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EIGRP Troubleshooting

1. 16 retransmits takes between 50 and 80 seconds 5 f a reliable packet is not acknowledged before 16 Neighbor 10 1 1 1 Ethernet0 is retransmissions and the down retry limit exceeded hold timer duration has passed re initialize the neighbor Ack Packet 2006 Cisco Systems Inc All rights reserved 12 Presentation_ID scr Retry Limit Exceeded The Retransmit Timeout RTO is used to determine when to retry sending a packet when an Ack has not been received and is generally based on 6 X Smooth Round Trip Time SRTT The SRTT is derived from previous measurements of how long it took to get an Ack from this neighbor The minimum RTO is 200 Msec and the maximum is 5000 Msec Each retry backs off 1 5 times the last interval The minimum time required for 16 retransmits is approximately 50 seconds minimum interval of 200 ms with a max interval of 5000 ms For example If there isn t an acknowledgement after 200 ms the packet is retransmitted and we set a timer for 300 ms If it expires we send it again and set the timer for 450 ms then 675 ms etc until 5000 ms is reached 5000 ms is then repeated until a total of 16 retransmissions have been sent The maximum time for 16 retransmits is approximately 1 minute 20 seconds if the initial retry is 5000 ms and all subsequent retries are also 5000 ms Retry Limit Exceeded f a reliable packet is retransmitted 16 times without an acknowledgement EIGRP checks to
2. In this example network the designer implemented manual summarization to hide the specific routes located at the remote sites by summarizing toward the core On each of the interfaces of router A and router B toward router X is the summary statement ip summary address eigrp 1 10 1 0 0 255 255 0 0 This blocks the specific prefixes from being advertised to X and instead only installs the 10 1 0 0 16 prefix there Normally this works great Minimal info is known at the core and proper routing takes place just fine But what happens if a problem occurs 2006 Cisco Systems Inc All rights reserved Presentation _ID scr 46 Black Hole Summary Routes He the Discard Route to null0 X is still receiving the summary from both A and B and may chose A as its path for packets going to 10 1 1 0 24 A builds a discard route to nullO with an administrative distance of 5 when the summary is configured The traffic will be dropped at A ip summary address eigrp 1 10 1 0 0 255 255 0 0 Black Hole Summary Routes Another problem we sometimes encounter when network designers listen to our recommendations is with summary black holes The problem is that a summary will be issued if any component of the summary exists If a router doing summarization loses access to one of the components of the summary it will still advertise reachability to the entire summary even though packets destined to the missing component cannot be de
3. Let s Look at a Problem in Progress What Does A Say About 20 1 1 0 24 20 1 1 0 24 rtrA show ip eigrp topology active IP EIGRP Topology Table for AS 1 ID 20 1 1 1 A 20 1 1 0 24 1 successors FD is Inaccessible 1 replies active 00 01 17 query origin Local origin via Connected Infinity Infinity Ethernet1 0 Remaining replies via Fe Ethernet0 0 10 1 3 0 24 A Is Waiting on B Chasing Active Routes In our example network we ve noticed dual 3 sia messages in the log of RTRA and we know the trigger is an unstable network off of this router instead of just shutting down the unstable link we decide to try to determine the cause of the stuck part of stuck in active In the above output we see that RTRA is active on the route 20 2 1 0 24 note the A in the left column and has been waiting for an answer from 10 1 1 2 RTRB for 1 minute and 17 seconds We know that we are waiting on RTRB because of the lower case r after the IP address Sometimes the lower case r comes after the metric in the upper part of the output not under remaining replies Don t be fooled The lower case r is the key not whether it s under the remaining replies are or not Since we know why we are staying active on the route because RTRB hasn t answered us we need to go to him RTRB to see why he s taking so long to answer 2006 Cisco Systems Inc All rights reserved 31 Presentation_ID scr Chasing Act
4. 2006 Cisco Systems Inc All rights reserved Presentation _ID scr 81
5. 4 Routing for Networks 40 80 0 0 16 92 168 107 0 Routing Information Sources Gateway Distance Last Update this router 90 00401710 40 80 24 33 90 01 13 47 40 80 12 19 90 01 13 47 40 80 23 31 90 01 13 48 40 80 8 13 90 01 13 48 Distance internal 90 external 170 2006 Cisco Systems Inc All rights reserved Presentation_ID scr Other Show Commands Show IP Protocol More show ip protocol stuff Summarization defined both auto and manual along with the metric associated with each summary Max path setting Network statements Distance settings Note that the Routing Information Sources section is really useless for EIGRP since it doesn t use periodic update we didn t rip it out of the display but there isn t much useful information for EIGRP in this section EIGRP Troubleshooting Summary Most problems seen in EIGRP networks are caused by factors outside of EIGRP itself congestion lack of summarization etc There are many tools and techniques available for troubleshooting problems in EIGRP networks 2006 Cisco Systems Inc All rights reserved 70 Presentation_ID scr Cisco Technical Support Website http www cisco com techsupport a i Product Support gt Tum to Cisco networking Use the Cisco Technical Tools res Support sute of tools and rex A comprehensive technicst Downloads pat je Advisor c Goounents Tor troubleshooting ware Bua Too dt c end optimizing n
6. as mentioned in the earlier section on stuck in active routes This number should be relatively low If it s not it s taking a bit of time for replies to be received for queries and it might be worth exploring why Other Show Commands Show IP Protocol rtrA show ip protocol xxx IP Routing is NSF aware Routing Protocol is eigrp 200 Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Default networks flagged in outgoing updates Default networks accepted from incoming updates EIGRP metric weight Kl 1 K2 0 K3 1 K4 0 K5 0 EIGRP maximum hopcount 100 EIGRP maximum metric variance 1 Redistributing eigrp 200 EIGRP NSF aware route hold timer is 240s EIGRP NSF enabled NSF signal timer is 20s NSF converge timer is 120s 2006 Cisco Systems Inc All rights reserved 68 Presentation_ID scr Other Show Commands Show IP Protocol There are many fields in the show ip protocol which are useful in the troubleshooting process Some of the most interesting include Outgoing and incoming filter lists Variance setting Redistribution configured note that if a router is not redistributing other protocols it still shows that it is redistributing itself NSF configuration and timers Other Show Commands Show IP Protocol Automatic network summarization is not in effect Address Summarization 40 0 0 0 8 for Vlan301 Summarizing with metric 1536 Maximum path
7. or whatever route is removed Routes that are active sometimes also show up as zero successor routes but they are transient and don t remain in that state This command isn t often used or useful 2006 Cisco Systems Inc All rights reserved 65 Presentation_ID scr Other Show Commands Show IP EIGRP Neighbor Detail Show ip eigrp neighbor detail is the big brother of the command shown earlier show ip eigrp neighbor some of the additional information available via the detailed version of this command include Number of retransmissions and retries for each neighbor Version of cisco IOS and EIGRP Stub information if configured rtr302 cel show ip eigrp neighbor detail IP EIGRP neighbors for process 1 H Address Interface Hold Uptime SRTT RTO OQ Seq Type sec ms Cnt Num 1 17 17 17 2 Et1 0 14 00 00 03 394 2364 0 124 Version 12 0 1 2 Retrans 0 Retries 0 Stub Peer Advertising CONNECTED SUMMARY Routes 0 50 10 10 1 Et0 0 13 04 04 39 55 330 0 13 Version 12 0 1 2 Retrans 2 Retries 0 Other Show Commands Show IP EIGRP Interface Detail rtrB show ip eigrp interface detail IP EIGRP interfaces for process 1 Xmit Queue Mean Pacing Time Multicast Pending Interface Peers Un Reliable SRIT Un Reliable Flow Timer Routes Et0 0 1 0 0 737 0 10 5376 0 Hello interval is 5 sec Next xmit serial lt none gt Un reliable mcasts 0 3 Un reliable ucasts 6 3 Mcast exceptions 0 CR packets 0 ACKs suppressed 0 Retransmis
8. B active timer Query all neighbors B The Active Process The normal converged state of routes in EIGRP is known as passive when a route goes active it means that EIGRP no longer has a known good loop free path for that destination and must actively look for a path to it This happens when the route goes down or increases in metric so that the best path is no longer feasible Note for a better definition of a feasible route check out the topology table explanations in the Troubleshooting Tools section later in this presentation When a route goes active EIGRP sends queries to all neighbors possibly limited by split horizon and sets a 1 5 minute timer 2006 Cisco Systems Inc All rights reserved 18 Presentation_ID scr The Active Process B receives As query 10 1 1 0 24 No FS mark route active Set 1 5 minute active timer 10 1 10 24 Gone No FS Query all neighbors C Query C receives B s query Examine local topology table 10 1 10 24 Gone No FS No feasible successors No neighbors to query en 10 1 10 24 Gone The Active Process When B receives the query from A it looks in its topology table to see if it has a feasible path to that destination in this example it doesn t find another path to the destination so it too goes active on the route B will then set its own 1 5 minute timer and send queries to all of its neighbors except the neighbor who it received th
9. easy in order to demonstrate the tools and techniques In a real event on a network there would probably be many more routes active and many more neighbors replying This can make chasing the waiting neighbors significantly more challenging Usually you will be able to succeed at tracking the waiting neighbors back to the source of the problem Occasionally you can t On highly redundant networks in particular you can find yourself chasing neighbors in circles without reaching an endpoint cause of the waiting If you run into this case you may need to temporarily reduce the redundancy in order to simplify the network for troubleshooting and convergence 2006 Cisco Systems Inc All rights reserved 38 Presentation_ID scr Likely Causes for Stuck in Active Bad or congested links Query range is too long Excessive redundancy Overloaded router high CPU Router memory shortage Software defects seldom Likely Causes for SIAs Remember that the cause of the SIA route could be a different location than where the SIA message and bounced neighbors happened This is particularly true with code older than CSCdp33034 Some of the possible causes of SIAs are Links that are either experiencing high CRC or other physical errors or are congested to the point of dropping a significant number of frames queries replies or acknowledgements could be lost The time it takes for a query to go from on
10. going down Holding time expired we didn t hear any EIGRP packets from this neighbor for the duration of the hold time this is typically 15 seconds for most media 180 seconds for low speed NBMA Retry limit exceeded this neighbor didn t acknowledge a reliable packet after at least 16 retransmissions actual duration of retransmissions is also based on the hold time but there were at least 16 attempts OUOU What Causes Neighbor Instability Holding time expired Retry limit exceeded Manual changes Stuck in active routes Not as many as there used to be more on this later 2006 Cisco Systems Inc All rights reserved Presentation_ID scr What Causes Neighbor Instability number of network events can cause neighbor instability With the use of the log neighbor changes messages you can track down many of the causes In this section we ll describe what causes some of these messages and resulting instability and how to fix them Note that with later code most manual changes no longer cause neighbors to bounce After CSCdy20284 many manual changes like summaries and filters now cause a resync between neighbors instead of a full blown neighbor down Quite an improvement Holding Time Expired The holding time expires when an EIGRP packet is not received during hold time Ping 224 0 0 10 Typically caused by congestion Hello or physical errors Ping the multicast address B
11. ip eigrp topology lt network gt lt mask gt In the above display you ll see that EIGRP not only stores which next hops have reported a path to the target network it stores the metric components used to reach the total composite metric You also may notice that EIGRP contains a hop count in the vector metrics The hop count isn t actually used in calculating the metric but instead was included to limit the apparent maximum diameter of the network In EIGRP s early days developers wanted to ensure that routes wouldn t loop forever and put this safety net in place In today s EIGRP it actually isn t necessary any longer but is retained for compatibility 2006 Cisco Systems Inc All rights reserved 63 Presentation_ID scr Topology Table Show IP EIGRP Topology Network Showing the topology table entry for an external route shows additional information about the route 1 10 200 1 0 RtrA show ip eigrp topology 30 1 1 0 255 255 255 0 IP EIGRP topology entry for 30 1 1 0 24 State is Passive Query origin flag is 1 1 Successor s FD is 46738176 Routing Descriptor Blocks 10 1 3 2 Seriall 2 from 10 1 3 2 Send flag is 0x0 Static Route to pe 30 1 1 0 24 Is External data H H Originating router is 64 1 4 14 Redistributed AS number of route is 0 into EIGRP External protocol is Static external metric is 0 Administrator tag is 0 0x00000000 Topology Table Show IP EIGRP Topology Network
12. of EIGRP development of ways to solve this problem dynamically A sys wish bug has been filed against it CSCdw68502 but we haven t started the work yet We re still discussing the best way to solve it 2006 Cisco Systems Inc All rights reserved Presentation _ID scr 48 Troubleshooting Tools The event log Debugs Show commands Cisco s technical support web site EIGRP Troubleshooting Tools Debugs Versus the EIGRP Event Log On a busy unstable network debugs can be hazardous to your network s health Event log is non disruptive already running 2006 Cisco Systems Inc All rights reserved 49 Presentation_ID scr EIGRP Troubleshooting Tools Two weapons at your disposal are debugs and the event log realize that the output of both debugs and the event log are cryptic and probably not tremendously useful to you so why am telling you about them There are times when the output of debugs or the event log is enough to lead you in a direction even if you don t really understand all that it is telling you don t expect to be an expert at EIGRP through the use of debugs or the event log but they can help Don t forget debugs can kill your router Don t do a debug if you don t know how heavy the overhead is may tell you below about some debugs but don t consider this approval from Cisco to run them on your production network The event log is non disruptive so it i
13. route events recorded when neighbors are cleared in reality the debugs produced were far far more This is only a snapshot of the debug modifier was included to limit the output to only the events related to a single EIGRP neighbor 10 1 6 2 Notice that the debug output doesn t identify which neighbors are involved in any of the events without knowing the address used in the modifier command you really can t tell which neighbors you are interacting with in the debug output This output is often useful when trying to determine what EIGRP thinks is happening when there are route changes in the network Debugs Debug IP EIGRP Route Events RTRA debug ip eigrp P EIGRP Route Events debugging is on RAtdebug ip eigrp 1 10 1 70 255 2552550 P Target enabled on AS 1 for 10 1 7 0 24 P EIGRP AS Target Events debugging is on H TRA clear ip eigrp neighbor P EIGRP 10 1 7 0 24 do advertise out Serial1 2 P EIGRP 10 1 7 0 24 do advertise out Serial1 1 RP Int 10 1 7 0 24 metric 20512000 20000000 512000 RP 10 1 7 0 24 do advertise out Seriall 2 RP Processing incoming UPDATE packet RP 10 1 7 0 24 do advertise out Seriall 1 HHH HHH TD H H De G G G G G G 2006 Cisco Systems Inc All rights reserved 55 Presentation_ID scr Debugs Debug IP EIGRP Route Events Again this is the output of debugging routing events this time modified to only display output related to a single route in the ne
14. see if the duration of the retries has reached the hold time as well Since the hold time is typically 15 sec on anything but low speed NBMA it normally isn t a factor in the retry limit NBMA links that are T1 or less however wait an additional period of time after re trying 16 times until the hold time period 180 seconds has been reached before declaring a neighbor down due to retry limit exceeded This was done to give the low speed NBMA networks every possible chance to get the Acks across before downing the neighbor 2006 Cisco Systems Inc All rights reserved 13 Presentation_ID scr Retry Limit Exceeded Ping the neighbor s unicast address A Vary the packet size Try large numbers of packets This ping can be issued from either neighbor the results should be the same B Common causes ee R Target IP address Mismatched MTU 101 E Repeat count 5 100 Unidirectional link Datagram Size 1500 Timeout in seconds 2 Dirty link Extended commands n y Manual Changes Some manual configuration changes can also reset EIGRP neighbors depending on the Cisco IOS version Summary changes manual and auto Route filter changes This is normal behavior for older code CSCdy20284 removed many of these neighbor resets Implemented in 12 2S 12 3T and 12 4 2006 Cisco Systems Inc All rights reserved 14 Presentation_ID scr EEE Manual Changes Summary changes When a summary changes on a
15. thing You do this through Summarization auto summary seldom used or manual summary to summarize within a major network or to summarize external routes Distribute lists used to limit knowledge of routes particularly on dual homed remotes which tend to reflect all routes back to the other leg of the dual home connection Use hierarchy if the network doesn t have hierarchy the two techniques above cannot adequately be used Define spoke edge routers as stubs so they aren t queried at all Run a Cisco IOS with CSCdp33034 included It changes the timing to decrease SIAs and push them closer to the source of the problem if they do occur 2006 Cisco Systems Inc All rights reserved 40 Presentation_ID scr External Routes External Routes The most common problem with external routes is EIGRP not installing them on some routers Router A is redistributing 10 1 1 0 24 10 1 1 0 24 via RIP but B and C do not have the route The first thing to check is whether pass i A has a redistribution metric ess configured via either Default metric lt metric gt C show ip route 10 1 1 0 2 Redistribute rip metric lt metric gt EIGRP can t pull metrics out of thin air so it won t redistribute routes unless it knows what B show ip route 10 1 1 0 metric to assign to them Bt 2006 Cisco Systems Inc All rights reserved 41 Presentation_ID scr External Routes EIGRP will automatically learn t
16. 224 0 0 10 from the other router 4 If there are a lot of interfaces or neighbors you should use extended ping and specify the source address or interface Neighbor 10 1 1 1 Ethernet0 is down holding time expired 2006 Cisco Systems Inc All rights reserved Presentation_ID scr EEE Holding Time Expired When an EIGRP packet is received from a neighbor the hold timer for that neighbor resets to the hold time supplied in that neighbor s hello packet then the value begins decrementing if you do several show ip eigrp neighbor commands you should see the hold time value changing The hold timer for each neighbor is reset back to the hold time when each EIGRP packet is received from that neighbor long ago and far way it needed to be a hello received but now any EIGRP packet will reset the timer Since hellos are sent every five seconds on most networks the hold time value in a show ip eigrp neighbors is normally between 10 and 15 resetting to hold time 15 decrementing to hold time minus hello interval or less then going back to hold time Why would a router not see EIGRP packets from a neighbor He may be gone crashed powered off disconnected etc He or we may be overly congested input output queue drops etc Network between us may be dropping packets CRC errors frame errors excessive collisions Holding Time Expiration RouterA debug eigrp packet hello EIGRP Packets debugging is on
17. 4 Router E sends F a query Router F examines its local tables D No information about 10 1 1 0 24 so send a reply Query is bounded because F has no information about 10 1 1 0 24 No Knowledge of H Route so Reply The Active Process As already mentioned a query will stop being propagated when the router receiving the query doesn t know anything about the prefix In the example above router E is using summarization to suppress sending 10 1 1 0 24 to router F when E receives the query from A and doesn t have a feasible path E will send a query to F F looks in his topology table and doesn t find any entries for 10 1 1 0 24 at all because he doesn t know anything about the prefix F immediately sends a reply with an infinity metric unreachable to E notifying him that the prefix is not reachable through him E can then reply to A that the prefix is not reachable through him either since the only reply he received declared the prefix unreachable 2006 Cisco Systems Inc All rights reserved 23 Presentation_ID scr The Active Process Router G has no other 10 1 1 0 24 neighbors Router A loses its connection to 10 1 1 0 24 Router A sends G a query Router G examines its local tables 7 No other oe F Neighbors No other neighbors to query so Reply so send a reply The Active Process A query will also stop being propagated when there are no other routers to ask In the e
18. 9707 19707 EIGRP Sending UPDATE on Seriall 1 nbr 10 1 2 2 AS 1 Flags 0x0 Seq 2832 1708 idbQ 0 0 iidbQ un rely 0 0 peerQ un rely 0 1 serno 19707 19707 EIGRP Sending UPDATE on Seriall 2 nbr 10 1 3 2 AS 1 Flags 0x0 Seq 2833 1680 idbQ 0 0 iidbQ un rely 0 0 peerQ un rely 0 1 serno 19707 19707 EIGRP Received ACK on Serial1 0 nbr 10 1 1 2 AS 1 Flags 0x0 Seq 0 2831 idbQ 0 0 iidbQ un rly 0 0 peerQ un rely 0 1 EIGRP Serial1 0 multicast flow blocking cleared EIGRP Received ACK on Serial1 1 nbr 10 1 2 2 AS 1 Flags 0x0 Seq 0 2832 idbQ 0 0 iidbQ un rely 0 0 peerQ un rely 0 1 EIGRP Serial1 1 multicast flow blocking cleared 2006 Cisco Systems Inc All rights reserved 57 Presentation_ID scr Debugs Debug IP EIGRP Notifications Debug ip eigrp notifications is used to troubleshoot p roblems with redistribution into EIGRP the callbacks describe what is happening between EIGRP a Rt p Rt Rt nd the routing table as routes are redistributed rA debug ip eigrp notifications EIGRP Event notification debugging is on rA clear ip route rA GRP Callback reload_iptable GRP iptable_redistribute into eigrp AS 1 GRP Callback redist frm static AS 0 100 100 100 0 24 into eigrp AS 1 event 1 EIGRP Callback redist frm static AS 0 200 200 200 0 24 into eigrp AS 1 event 1 A ww Debugs Debug EIGRP FSM Finite State Machine RTRA debug eigrp fsm EIG RP FSM Events Actions debugging is on R
19. A Query Process What if B doesn t reply to 10 1 1 0 24 A within 1 5 minutes the active timer 10 1 10 24 Gone No FS A sends an SIA query A If B responds to the SIA query Query with an SIA reply A resets its timer and the A B neighbor relationship lex stays up B 10 1 10 24 Gone No FS B s relationship with C will fail at some point 3 Query Bad Link This clears the query __ Reply Never from B s point of view Reply Makes It B replies to A c 10 1 10 24 Gone Remove 10 1 1 0 24 The SIA Query Process Sometimes the active process doesn t complete normally This can be due to a number of different problems which are covered later in this presentation What happens when things go wrong f B doesn t respond to A within 1 5 minutes because it s waiting for a reply from C A will send an SIA query to B checking the status If B is still waiting on answer itself it will respond to A with an SIA reply This resets the SIA timer on A so it will wait another 1 5 minutes Eventually the problem keeping C from responding to B will take the neighbor relationship down between B and C which will cause B to reply to A ending the query process 2006 Cisco Systems Inc All rights reserved 26 Presentation _ID scr EaEaa_ _ The SIA Query Process SIA queries are sent to a neighbor up to three times May attempt to get a reply from a neighbor for a total of six minutes If still no reply
20. D scr TAC Case Collection Tool will clarify Cisco Systems st the problem area Edit problem type if query has been m I S u n d e rstood Your query is EIGRP router not establishing neighbors lunderstood Problem Type Edit Select which of the following best describes Not forming neighbors your problem IP Routing Protocols Edit Which of the following protocols does the EIGRP problem apply to Los coe a TAC Case Collection On this query confirmation page here the tool will clarify the problem area you also have the opportunity to edit the problem type if your query has been misunderstood In our example though the tool correctly understood my problem and identified EIGRP as the IP routing protocol associated with my problem Upon clicking the next button the search is submitted to the TAC Case Collection solution database 2006 Cisco Systems Inc All rights reserved 77 Presentation_ID scr DO TAC Case Collection A Search resu Its table Cisco Si now a Click View Solution links to be taken to solution s FREE TEXT QUERY VIEW ALL SOLUTIONS Knowledge Base IP Routing Showing 1 1 oft resus lt Prev Page 1 Z Next Your Search D 1 100 EIGRP neighbors are not forming over the secondary network Problem Not Not forming neighaors Neighbor issues Type forming eighbors IP Routing BGRP EIGRP Additional Details
21. HELLO 19 08 38 521 EIGRP Sending HELLO on Seriall 1 19 08 38 521 AS 1 Flags 0x0 Seq 0 0 idbQ 0 0 iidbQ un rely 0 0 19 08 38 869 EIGRP Received HELLO on Serial1 1 nbr 10 1 6 2 19 08 38 869 AS 1 Flags 0x0 Seq 0 0 idbQ 0 0 iidbQ un rely 0 0 19 08 39 081 EIGRP Sending HELLO on FastEthernet0 0 19 08 39 081 AS 1 Fags 0x0 Seq 0 0 idbQ 0 0 iidbQ un rely 0 0 Remember Any Debug Can Be Hazardous 2006 Cisco Systems Inc All rights reserved Presentation _ID scr 10 EEE Holding Time Expired Another troubleshooting tool available is to do the debug command debug eigrp packet hello this will produce debug output to the console or buffer log depending on how you have it configured that will show the frequency of hellos sent and received You should make sure you have the timestamps for the debugs set to a value that you can actually see the frequency something like service timestamps debug datetime msec Remember that any time you enable a debug on a production router you are taking a calculated risk It s always better to use all of the safer troubleshooting techniques before resorting to debugs Sometimes they re necessary however Retry Limit Exceeded EIGRP sends both unreliable and reliable packets Hellos and acks are unreliable Updates queries replies SIA queries and SIA replies are reliable Reliable packets are sequenced and require an acknowledgement Reliable packets are retra
22. How are Connected via LAN switch es Connected da Frame Relay bors Connected show ip Neighbor does not exist in neighbor table TAC Case Collection And we get to the search results table which shows one solution at 100 similarity a By clicking the View Solution link lII be taken to my solution 2006 Cisco Systems Inc All rights reserved Presentation _ID scr 78 TAC Case Collection nary address on Me interface is oi on command This network soul ehwork covers the Secondary IP address assigned to nterface e0 Alhough the 121 102 0 0 newer seighiber aver this network Hin 13110 o O newerk is in BORP EIGRP wil not farm a n owes the 131 50200 network is advertised nie secon of Enhanced Protieu Type Not forming nalgr ors Neighbor issues P Roming Protocuts ERP How aro Neighbors Connected via LAN stichies Connerled Connecid show app Neigngor does nat esist m neighbor table neaghbors TAC Case Collection And here the tool has provided us with a detailed solution page where we see the solution number title core issue resolution along with links to other resources As a reminder I d reiterate that the solutions presented here are from actual service requests taken by TAC engineers Before leaving the TAC Case Collection I d like to mention that there is a feedback form on the left hand side of the page beside the detailed solution we invite you to please take a few mo
23. ID scr Topology Table Show IP EIGRP Topology Zero Zero successor routes are those that fail to get installed in the routing table by EIGRP because there is a route with a better admin distance already installed 1 10 200 1 0 RtrA show ip eigrp topology zero IP EIGRP Topology Table for AS 1 ID 10 1 6 1 P 10 200 1 0 24 0 successors FD is Inaccessible via 10 1 1 2 21026560 20514560 Serial1 0 via 10 1 2 2 46740736 20514560 Serial1 1 via 10 1 3 2 46740736 46228736 Serial1 2 RtrA show ip route 10 200 1 0 255 255 255 0 Static Route to Routing entry for 10 200 1 0 24 10 200 1 0 24 Known via static distance 1 metric 0 Through RtrB Routing Descriptor Blocks 10 1 1 2 Route metric is 0 traffic share count is 1 Show IP EIGRP Topology Zero And last the show ip eigrp topology zero command is available to display the topology table entries that are not actually being used by the routing table Typically zero successor entries are ones that EIGRP attempted to install into the routing table but found a better alternative there already In our example above when EIGRP tried to install its route with an administrative distance of 90 it found a static route already there with an administrative distance of one and thus couldn t install it In case the better route goes away EIGRP retains the information in the topology table and will try to install the route again if it is notified that the static
24. IGRP Topology Table for AS 7 ID 192 168 1 1 If your event log is big enough or things are slow enough you might see the problem indicated in your even log 1 02 30 18 591 Ignored route metric 192 168 1 0 2297856 2 02 30 18 591 Ignored route neighbor info 10 0 24 Serial0 3 3 02 30 18 591 Ignored route dup router 192 168 1 1 2006 Cisco Systems Inc All rights reserved 44 Presentation_ID scr External Routes The EIGRP router ID is derived from The router id command Lowest numbered loopback interface Highest local interface IP address if no loopbacks Once the router ID is set it won t be changed without manual intervention even if the interface from which it s taken is removed from the router Impact on external routes EIGRP includes the router ID of the originating router in external routing information If a router receives an external route with a router ID matching its own local router ID it discards the route This prevents routing loops in externally derived routes Aggregation 2006 Cisco Systems Inc All rights reserved 45 Presentation_ID scr OU Black Hole Summary Routes This network implements manual summarization from the distribution routers toward the core 10 1 1 0 24 It normally doesn t matter whether A or B is used to reach a remote from X 10 1 2 0 24 10 1 3 0 24 ip summary address eigrp 1 10 1 0 0 255 255 0 0 OOUE Black Hole Summary Routes
25. If you perform the command show ip eigrp topology lt network gt lt mask gt for an external route one redistributed into EIGRP from another protocol even more information is displayed The initial part of the display is identical to the command output for an internal native route The one exception is the identifier of the route as being external Another section is appended to the first part however containing external information The most interesting parts of the external data are the originating router and the source of the route The originating router is the router who initially redistributed the route into EIGRP Note that the value for the originating router is router id of the source router which doesn t necessarily need to belong to an EIGRP enabled interface The router id is selected in the same way OSPF selects router ids starting with loopback interfaces if any are defined or using the highest IP address on the router if there aren t loopback interfaces Note that if a router receives an external route and the originating router field is the same as the receiver s router id he rejects the route This is noted in the event log as ignored dup router The originating routing protocol where it was redistributed from is also identified in the external data section This is often useful when unexpected routes are received and you are hunting the source 2006 Cisco Systems Inc All rights reserved 64 Presentation _
26. RE e 1 EIGRP Troubleshooting BRKRST 3330 2006 Cisco Systems Inc All rights reserved Presentation _ID scr Networkers fre e ET efo ern Cisco Networkers i EIGRP Troubleshooting Neighbors The Active Process External Routes Aggregation Troubleshooting Tools Neighbors 2006 Cisco Systems Inc All rights reserved Presentation _ID scr Troubleshooting EIGRP Neighbors Neighbor process Checking neighbor status Log neighbor changes Holding time expired Retry limit exceeded Manual changes Unidirectional links Primary secondary mismatch Neighbor Process Hello process used for neighbor discovery and maintenance Multicast hellos by default 224 0 0 10 Hello 0100 5e00 000a Hello interval 60 seconds for low speed NBMA 5 seconds for all other interfaces 2006 Cisco Systems Inc All rights reserved Presentation_ID scr Neighbor Process The hello process has two distinct purposes Neighbor discovery When a hello packet is seen on an interface with EIGRP enabled EIGRP looks at the information in the hello to see if it s legal for the sender to become a neighbor The IP address must be a member of the same subnet the AS number must match and the k values must match If the sender is legal and isn t currently in the neighbor table it is put into the neighbor table and the neighbor initialization proc
27. TRA clear ip route RTRA DUA DUA DUA DUA DUA DUA L Find FS for dest 10 1 8 0 24 FD is 28160 RD is 28160 Li 0 0 0 0 metric 28160 0 found Dmin is 28160 L Find FS for dest 10 1 3 0 24 FD is 21024000 RD is 21024000 L 10 1 6 2 metric 21024000 2169856 found Dmin is 21024000 L RT installed 10 1 3 0 24 via 10 1 6 2 L Find FS for dest 10 1 2 0 24 FD is 21536000 RD is 21536000 2006 Cisco Systems Inc All rights reserved 58 Presentation _ID scr Debugs Debug EIGRP FSM Debug eigrp fsm is very very similar to dual event log since the dual event log is non disruptive and this debug could certainly cause problems rarely use this debug FSM stands for Finite State Machine which describes the behavior of DUAL the path selection part of EIGRP Topology Table The topology table is probably the most critical structure in EIGRP Contains building blocks used by DUAL Used to create updates for neighbors populate routing table Understanding the topology table contents is extremely important in troubleshooting EIGRP problems 2006 Cisco Systems Inc All rights reserved 59 Presentation_ID scr Topology Table One of the reasons that EIGRP is called an advanced distance vector protocol is that it retains more information than just the best path for each route it receives This means that it can potentially make decisions more quickly when changes occur because it has a more complete
28. at anytime by selecting the submit button Also for a free text query the tool will switch to Guided Search if additional information is required to narrow the search or if the tool did not understand the entry Otherwise if your query is understood by the tool from the outset you could end up saving time because you will have started from a later stage in the search process as you work toward reaching the solutions So let s run the search for our example now 2006 Cisco Systems Inc All rights reserved 75 Presentation_ID scr TAC Case Collection Free Text Query Cont Problem Type Tor indi Ni Cisco Systems 0058 Window v E Feedback Help FREE TEXT QUERY GUIDED SEARCH VIEW ALL SOLUTIONS Knowledge Base IP Routing Your Search Free Te y Please enter your query EIGRP router not establishing neighbors Select which of the following best describes your problem Network not being propagated advertised I E Neighbor issues I Avoid neighbors on an interface I Neighbors flapping Router not forwarding packets tat covet se et C O O O e TAC Case Collection The tool understands the query correctly EIGRP Router not establishing neighbors and selects not forming neighbors as the problem type we click next to get the following screen as we work through the tool 2006 Cisco Systems Inc All rights reserved Presentation_I
29. ble packet from this peer RTO Retransmit Time Out how long to wait between retransmissions if Acks are not received from this peer Checking Neighbor Status EIGRP Log Neighbor Changes is on by default since 12 2 12 Turn it on and leave it on Best to send to buffer log RouterA config terminal Enter configuration commands one per line End with CNTL Z RouterA config router eigrp 1 RouterA config router eigrp log neighbor changes RouterA config router logging buffered 10000 RouterA config service timestamps log datetime msec 2006 Cisco Systems Inc All rights reserved Presentation_ID scr Checking Neighbor Status EIGRP log neighbor changes is the best tool you have to understand why neighbor relationships are not stable It should be enabled on every router in your network CSCdx67706 12 2 12 made it the default behavior As explained on the previous slide the uptime value from show ip eigrp neighbors will tell you the last time a neighbor bounced but not how often or why With log neighbor changes on and logging buffered you keep not only a history of when neighbors have been reset but the reason why Absolutely invaluable Logging buffered is also recommended because logging to a syslog server is not bulletproof For example if the neighbor bouncing is between the router losing neighbors and the syslog server the messages could be lost It s best to keep these types of messages local
30. by the end of this process consider the route stuck through this neighbor On the router that doesn t get a reply after three SIA queries Reinitializes neighbor s who didn t answer Goes active on all routes known through bounced neighbor s Re advertises to bounced neighbor all routes that we were advertising Stuck in Active Routes SIA DUAL 3 SIA Route 10 64 5 0 255 255 255 192 stuck in active state in IP EIGRP 100 Cleaning up Indicates at Least Two Problems A route went active It got stuck 2006 Cisco Systems Inc All rights reserved Presentation_ID scr OUUU Troubleshooting SIAs Two probably unrelated causes of the problem stuck and active Need to troubleshoot both parts Cause of active often easier to find Cause of stuck more important to find Troubleshooting SIAs If routes never went active in the network we would never have to worry about any getting stuck Unfortunately in a real network there are often link failures and other situations that will cause routes to go active One of our jobs is to minimize them however If there are routes that regularly go active in the network you should absolutely try to understand why they are not stable while you cannot ensure that routes will never go active on the network a network manager should work to minimize the number of routes going active by finding and resolving the causes Even if you reduce the number of routes going ac
31. d 10 1 3 0 24 C Is Waiting on D Chasing Active Routes Step 2 On RTRC we repeat the show ip eigrp topology active command and see what he thinks of the route Again he s waiting on another neighbor downstream to answer him before he can answer RTRB You are probably getting the idea of how exciting this process can be Of course in a real network you probably have users managers breathing down your neck making it a bit more interesting As l m sure you suspect our next step should be to see why 10 1 3 2 RTRD isn t answering RTRC s query 2006 Cisco Systems Inc All rights reserved 33 Presentation_ID scr Chasing Active Routes Step 3 Why Isn t D Answering 20 1 1 0 24 rtrD show ip eigrp topology active IP EIGRP Topology Table for AS 1 ID 10 1 3 2 rtrD Wow He Doesn t Even Know There Was a Question Asked Maybe He s Already Answered 10 1 3 0 24 Chasing Active Routes Step 3 And again we look at the active topology table entries this time on RTRD Wait RTRD isn t waiting on anyone for any routes Did the replies finally get returned and the route is no longer active We need to go back to RTRC and see if he is still active on the route 2006 Cisco Systems Inc All rights reserved 34 Presentation_ID scr Chasing Active Routes Step 4 No C Is Still Waiting on D What s the Deal 20 1 1 0 24 10 1 2 0 24 rtrC show ip eigrp top
32. d none of the replies contained an alternative path to the destination it will remove the prefix from its topology table and routing table The network is now converged on the new information 2006 Cisco Systems Inc All rights reserved 20 Presentation_ID scr The Active Process Where do queries stop 10 1 1 0 24 Router A loses its connection to 10 1 1 0 24 A Router sends B a query Local Knowledge of an Alternate Path so Reply Router B examines its local tables and finds C Its current path successor doesn t pass through A Router B answers with a valid alternative path The query is bounded where there is local knowledge of another loop free path C O O Oek The Active Process Since queries are used to find an alternative path to a lost destination where do these queries stop or do they just keep circulating through the network One place where a query will stop propagating is where the router receiving the query has an alternative path that it can reply with n the example above B receives the query from A looks in his topology table and finds that he has a loop free path to the destination B will reply to A with the metric he is using for that destination so that A can install the path through him to reach the destination There s no need to send the query on when you have a good answer yourself 2006 Cisco Systems Inc All rights reserved 21 Presentation _ID sc
33. due to retry limit exceeded Now we need to use our normal troubleshooting methodology to determine why these two routers can t talk to each other properly 2006 Cisco Systems Inc All rights reserved 36 Presentation_ID scr Chasing Active Routes Step 6 Let s Check General Reachability 20 1 1 0 24 rtrC ping 10 1 3 2 aed cenit ec Sending 5 100 byte ICMP Echos to 10 1 3 2 timeout is 2 seconds uccess rate is 0 percent 0 5 10 1 3 0 24 Okay We Can t Ping We Need to Fix This Before EIGRP Stands a Chance of Working Chasing Active Routes Step 6 How does basic connectivity look A ping between RTRC and RTRD isn t succeeding either We ll need to find out why they can t talk to each other Whatever is causing them to not talk to each other is undoubtedly a contributing factor to the SIAs we re seeing in the network we need to find and fix the problem with this link and remove the cause of the SIA routes 2006 Cisco Systems Inc All rights reserved 37 Presentation_ID scr Troubleshooting the Stuck Part of SIAs It s not always this easy to find the cause of an SIA Sometimes you chase the waiting neighbors in a circle If so summarize and simplify Easier after CSCdp33034 SIA should happen closer to the location of the cause of the problem a aa Troubleshooting the Stuck Part of SIAs Our example of chasing SIA routes was intentionally made very
34. e default hold time for low speed NBMA networks is 180 seconds 3 X 60 second hellos and 15 seconds for all other interface types 3 X 5 seconds Note if you change the hello interval using the ip hello interval eigrp 1 lt num gt command it does not automatically change the hold time to 3 X the new value you must also set the hold time to the value desired Note CSCdr96531 changed the neighbor establishment process to make it much more reliable Checking Neighbor Status RTRA show ip eigrp neighbors IP EIGRP neighbors for process 1 H Address Interface Hold Uptime SRTT RTO Q Seq sec ms Cnt Num 2 10 1 1 1 Eto 233 1 10 1 4 3 BEL 13 452 0 10 1 4 2 Etl 3 Seconds Remaining Before Declaring Neighbor Down How Long Since the Last Time Neighbor Was Discovered How Long It Takes for This Neighbor to Respond to Reliable Packets How Long We ll Wait Before Retransmitting If No Acknowledgement 2006 Cisco Systems Inc All rights reserved Presentation_ID scr EEE Checking Neighbor Status The most useful command for checking neighbor status is show ip eigrp neighbors Some of the important information provided by this command are Hold time time left that you ll wait for an EIGRP packet from this peer before declaring him down Uptime how long it s been since the last time this peer was initialized SRTT Smooth Round Trip Time average amount of time it takes to get an Ack for a relia
35. e end of the network to the other is too long and the active timer expires before the query process completes don t think I ve ever seen a network where this is true by the way The complexity in the network is so great due to excessive redundancy that EIGRP is required to work so hard at sending and replying to queries that it cannot complete them in time A router is low on memory so that it is able to send hellos which are very small but be unable to send queries or replies There have occasionally been software defects that caused SIAs CSCdi83660 CSCdv85419 2006 Cisco Systems Inc All rights reserved Presentation_ID scr 39 EEE Minimizing SIA Routes Decrease query scope involve fewer routers in the query process Summarization manual or auto Distribute lists Define spoke edge routers as stubs Run a Cisco IOS which includes CSCdp33034 Minimizing SIA Routes Weve now talked about the impart that SIA routes can cause on your network and how to track down the cause of SIA events while you may not be able to completely rid your network of SIA routes there are techniques you can use to minimize your exposure Decrease query scope in our example network you saw the queries sent to each router in a chain As explained earlier if a router received a query on a route that it doesn t have in its topology table it immediately answers and doesn t send the query onward This is a very good
36. e query from its previous successor in this case C is the only neighbor to ask C receives the query from B and checks its own topology table to see if it has a feasible path to the destination it doesn t have a feasible route and also doesn t have any other neighbors to ask Note that up to this point B has not replied A and C has not replied B 2006 Cisco Systems Inc All rights reserved 19 Presentation_ID scr The Active Process Chas no alternate path to 10 1 1 0 24 Remove from local tables Reply to querying neighbors B receives C s reply No outstanding queries Remove from local tables 10 1 1 0 24 10 1 10 24 Gone No FS Remove 10 1 1 0 24 Query Reply 10 1 10 24 Gone No FS Remove 10 1 1 0 24 Query Reply 10 1 10 24 Gone Remove 10 1 1 0 24 Reply to querying neighbors A receives B s reply No outstanding queries Remove from local tables The Active Process Since C doesn t have any other neighbors to ask it deletes the prefix that was active from both the topology table and routing table then sends a reply to B notifying it that it doesn t have a path to the destination When B receives replies to all of its queries in this case only from C B will remove the prefix from its topology table and routing table and send a reply to A notifying it that it doesn t have a path to the destination When A receives replies to all of its queries from B an
37. ery Please enter a brief description of your problem or question and click the Submit button Search Tips EIGRP router not establishing neighbors Guided Search Use the Guided Search to step through a series of questions to arrive atthe most relevant solutions TAC Case Collection With that background let s look at how to use the tool Clicking the IP Routing Protocols link from the previous jump page brings me here to a new child window In the upper right of the page you d see the knowledge base selected in our example IP Routing First let s focus our attention on how to perform a free text query highlighted in the top white tab You will notice that Guided Search and View All solutions are the next tabs highlighted in green So basically the free text field is where youd type in a description of the problem or question EIGRP router not establishing neighbors and then click the Submit button to begin the search The application then parses the information in the query and in some instances will prompt you for further information via refining questions The tool continues to ask questions until the search results are narrowed to three or fewer at 100 similarity and then will present a search results table as we work through the tool to get to our solutions I d like to point out that while you can continue to narrow your search by clicking the next button you can also view search results
38. ess is started Neighbor maintenance Once a neighbor relationship is established hello packets are sent in order to keep the neighbor relationship alive Since EIGRP doesn t send periodic updates the hello process is used to keep track of which neighbors are still functioning As long as hellos are seen from a neighbor his routes are considered still valid Neighbor Process Hold timer How long to wait without hearing an EIGRP packet from a neighbor before declaring it dead Value contained in hello packets sent by each router Defaults to 3 X hello interval 15 seconds on most interfaces RTRB show ip eigrp neighbors H Address Interface Hold sec 2 A Eto D 180 seconds on low speed NBMA 2006 Cisco Systems Inc All rights reserved Presentation _ID scr Neighbor Process The hold timer defines how long to wait without hearing an EIGRP packet from a neighbor before declaring them down prior to CSCdi36031 it had to a hello received that DDTs changed it so that any EIGRP packet will reset the timer though normally it s still a hello that keeps the neighbor relationship alive Each EIGRP router includes its own hold time in the hellos it sends This allows it to define how long its neighbors should wait for it This allows us to have different hello hold timers on routers on the same subnet unlike OSPF or IS IS The hold time defaults to 3 X the default hello intervals therefore th
39. etworks gt gt ire securty Advisories amp wene Cross a nie TAC Sandon Roques Rept Product Secutly Inciderts Scout Adhiseries Cisco Technical Support Web Site This is the Cisco Technical Support Website To access the range of useful support tools and documentation on the site at www cisco com techsupport please be sure to log in with your registered cisco com user name and password If you are not a registered user and would like information about what is needed to register at Cisco com e g a service contract please click the Register tab at the top of the page The Technical Support site is divided into modules The first two modules Product Support and Technology Support under Documentation and Tools contain all the technical content on the Cisco Technical Support Website These two modules provide an intuitive and easy way to navigate to all the technical documents and tools on the site Also in this screen capture are additional modules that provide fast access to specific types of information on the site for example the Tools section links to useful online support tools and in the upper right of the home page we now have links to some of our top tools under Featured Tools You ll also see on the home page a link to software downloads called Downloads and a section to Contact Cisco for Support that include links to the TAC Service Request Tool to create a new service req
40. f routes going active as dial in users connect and disconnect Are links flapping bouncing up and down causing the routes and everything behind it to regularly go active Are most or all of the routes coming from the same area of the network If so you need to determine what is common in the topology to them so that you can determine why they are not stable 2006 Cisco Systems Inc All rights reserved 29 Presentation_ID scr E UUT Troubleshooting the Stuck Part of SIAs Show ip eigrp topology active Useful only while the problem is occurring f problem isn t occurring at the time it is difficult to find the source of routes getting stuck OOl Troubleshooting the Stuck Part of SIAs Our best weapon to use to find the cause of routes getting stuck in active is the command show ip eigrp topology active it provides invaluable information about routes that are in transition Examples of the output of this command and how to evaluate it will be in the next several slides Unfortunately this command only shows routes that are currently in transition It probably isn t useful after the fact when you are trying to determine what happened earlier If you aren t chasing it while the problem is occurring there aren t really any tools that will help you find the cause 2006 Cisco Systems Inc All rights reserved 30 Presentation_ID scr Chasing Active Routes Why Is A Reporting SIA Routes
41. hat the router on the right exists RtrA is sending out his hellos waiting for a neighbor to show up on the network What he doesn t realize is that the rtrB is already out there and trying to bring up the neighbor relationship RtrB on the other hand sees the hellos from rtrA sends his own hellos and then sends an update to rtrA to try to get their topology tables routing tables populated Unfortunately since the updates are also not being received by rtrA it of course isn t sending acknowledgements RtrB tries it 16 times and then resets his relationship with rtrA and starts over You ll spot this symptom by the retry limit exceeded messages on rtrB rtrB having rtrA in his neighbor table with a continual Q count and rtrA not seeing rtrB at all CSCdy45118 has been implemented to create a reliable neighbor establishment process three way handshake and reliable neighbor maintenance neighbor taken down more quickly when unidirectional link encountered 12 2T 12 3 and up Primary Secondary Mismatch IP EIGRP Neighbor neighbor 10 1 1 1 not on common subnet for Ethernet 1 EIGRP always sources Primary 10 1 1 1 24 packets from the Secondary 192 168 1 1 24 primary interface address f a router receives an EIGRP packet with a source address not on the subnet for that dre pre interface Primary 192 168 1 3 24 The adjacency won t be formed The receiving router will print log messages indicating the primar
42. he redistributing router matches the router id of the router refusing to install the route To block routing loops a router doing redistribution will not accept a route from a neighbor if he is the one that originated it this is known by the originating router field in the external data section of the topology table entry Since the router ids are the same on router A and router C router C thinks router A s external routes originated on router C and he rejects them 2006 Cisco Systems Inc All rights reserved 43 Presentation_ID scr External Routes In older versions of Cisco IOS Software the only way to find out a router s router ID was to go to an adjacent router and look for some redistributed route from that router f there isn t anything being redistributed redistribute something router show ip eigrp topology 10 1 1 0 255 255 255 0 IP EIGRP AS 7 topology entry for 10 1 1 0 24 State is Passive Query origin flag is 1 1 Successor s FD is 2560000256 Routing Descriptor Blocks 10 1 2 1 Ethernet0 0 via 10 1 2 1 Send flag is 0x0 Composite metric is 2560000256 0 Route is External External data Originating router eee AS number of route is 0 External protocol is RIP external metric is 1 Administrator tag is 0 0x00000000 External Routes In newer versions of Cisco IOS Software a router s router ID is listed in the output of show ip eigrp topology router 1 show ip eigrp topology IP E
43. he redistribution metrics from A connected interface for redistribute connected The interface through which a static route is reached for redistribute static note this isn t always reliable You re better off still specifying the redistribution metric The metric of an IGRP route in the same AS The metric of an EIGRP route from another AS If none are those are true you must supply the metric for redistribution External Routes We ve resolved the redistribution metric issue on A and B is now receiving the route but C isn t why 10 1 1 0 24 via RIP a FI ean router eigrp 100 redistribute rip default metric C show ip route 10 1 1 0 B show ip route 10 1 1 0 10 1 1 0 24 via A 2006 Cisco Systems Inc All rights reserved 42 Presentation _ID scr External Routes Looking at B s topology table we can see the originating router ID field in the external route is set to 192 168 1 1 But that s router C s loopback address 10 1 1 0 24 via RIP a T B show ip eigrp topology 10 1 1 0 IP EIGRP AS 1 topology entry for 10 10 1 0 24 External data Originating router is External Routes In the example above we have a problem where routes are being redistributed just fine but one router elsewhere in the network is refusing to install the external routes into its topology table or routing table As the slide shows the problem is that the router id of t
44. hts reserved 60 Presentation_ID scr Topology Table Show IP EIGRP Topology Show ip eigrp topology displays a list of successors and feasible successors for all destinations known by EIGRP 1 10 200 1 0 RtrA show ip eigrp topology D IP EIGRP Topology Table for AS 1 ID 10 1 6 1 SAP P 10 200 1 0 24 1 successors FD is 21026560 m Feasible Distance via 10 1 1 2 21026560 20514560 Seriall 0 Successor via 10 1 2 2 46740736 20514560 Seriall1 1 Feasible Successor Computed Reported Distance Distance Topology Table Show IP EIGRP Topology The most common way to look at the topology table is with the generic show ip eigrp topology command this command displays all of the routes in the EIGRP topology table along with their successors and feasible successors In the above example the P on the left side of the topology entry displayed means the route is Passive If it has an A it means the route is Active The destination being described by this topology entry is for 10 200 1 0 255 255 255 0 This route has one successor and the feasible distance is 21026560 The feasible distance is the metric that would appear in the routing table if you did the command show ip route 10 200 1 0 255 255 255 0 Following the information on the destination network the successors and feasible successors are listed The successors one or more are listed first then the feasible successors a
45. ive Routes Step 1 So Why Hasn t B Replied 20 1 1 0 24 rtrB show ip eigrp topology active IP EIGRP Topology Table for AS 1 ID 10 1 2 1 A 20 1 1 0 24 1 successors FD is Inaccessible 1 replies active 00 01 26 query origin Successor Origin via 10 1 1 1 Infinity Infinity Ethernet0 0 Remaining replies via 10 1 2 2 Ethernet1 0 10 1 3 0 24 B Is Waiting on C Chasing Active Routes Step 1 We repeat the show ip eigrp topology active command on RTRB and we get the results seen above We see that RTRB probably isn t the cause of our stuck in active routes since he is also waiting on another router downstream to answer his query before he can reply again the lower case r beside the IP address of 10 1 2 2 tells us he is the neighbor slow to reply We now need to go to 10 1 2 2 RTRC and see why he isn t answering RTRB 2006 Cisco Systems Inc All rights reserved 32 Presentation_ID scr Chasing Active Routes Step 2 What s C s Problem 10 1 1 0 24 20 1 1 0 24 rtrC show ip eigrp topology active IP EIGRP Topology Table for AS 1 ID 10 1 3 1 Codes P Passive A Active U Update Q Query R Reply r reply Status s sia Status A 20 1 1 0 24 1 successors FD is Inaccessible Qqr 1 replies active 00 01 33 query origin Successor Origin retries 1 via 10 1 2 1 Infinity Infinity Ethernet0 0 serno 20 via 10 1 3 2 Infinity Infinity q Ethernet1 0 serno 19 anchore
46. livered This isn t a problem if the summarizing router is the only path the lost network but often it s not In the diagram above both rtrA and rtrB have access to the remotes and are Summarizing them toward the core of the network If rtrA loses access to 10 1 1 0 24 routers downstream like rtrX could send packets to rtrA that he cannot deliver If the packets went to rtrB however they would have been delivered successfully 2006 Cisco Systems Inc All rights reserved Presentation_ID scr 10 1 2 0 24 10 1 1 0 24 10 1 3 0 24 47 Black Hole Summary Routes Possible Solutions Add a new link between New Link No Summarization A and B without F summarization configured 7 10 1 1 0 24 Add a GRE tunnel between A and B without summarization configured 10 1 2 0 24 GRE Tunnel No Summarization 10 1 3 0 24 ip summary address eigrp 1 10 1 0 0 255 255 0 0 Black Hole Summary Routes The normal method to avoid resolve this problem is to have another link between summarizing routers another Fast Gig Ethernet PVC etc and not summarize across this link in that way rtrA would be getting component routes from rtrB and would know how to deliver packets to 10 1 1 0 through rtrB Another approach used if the cost of another link is too high is to put a GRE tunnel between rtrA and rtrB and allow all component routes to be advertised across this tunnel There s also some discussion inside
47. ly on the router in addition to the syslog server t may also be useful to increase the size of the buffer log in order to capture a greater duration of error messages You would hate to lose the EIGRP neighbor messages because of flapping links filling the buffer log If you aren t starved for memory change the buffer log size using the command logging buffered 10000 in configuration mode The service timestamps command above puts more granular timestamps in the log so it s easier to tell when the neighbor stability problems occurred Log Neighbor Changes Messages So this tells us why the neighbor is bouncing but what do they mean Hint peer restarted means you have to ask the peer he s the one that restarted the session Neighbor 10 1 1 1 Ethernet0 is down peer restarted Neighbor 10 1 1 1 Ethernet0 is up new adjacency Neighbor 10 1 1 1 Ethernet0 is down holding time expired Neighbor 10 1 1 1 Ethernet0 is down retry limit exceeded Neighbor 10 1 1 1 Ethernet0 is down route filter changed Others but not often 2006 Cisco Systems Inc All rights reserved Presentation_ID scr Log Neighbor Changes Messages Peer restarted the other router reset our neighbor relationship you need to go to him to see why he thought our relationship had to be bounced New adjacency established a new neighbor relationship with this neighbor happens at initial startup and after recovering from a neighbor
48. mentation Neighbor check a 7 P S No Main Troubleshooting Flowchart mg EI RP Neighbor Chack route sme p TRES k Main j A 7 Canyou successtulyping N x K bewoon neighbors with pacit gt Z N faces up to interface MTU size Which symptom on N Yes Nig A best describes your problem No Y Local EIGRP router not establishing EIGRP neighbors with neighboring router EIGRP Neighbor Check y Routes static dynamic not being EIGRP Redistribution redistributed into EIGRP Check Routes missing from routing table show ip route x x x x command displays nothing s For more information see What Do EIGRP Not On Receiving Not on Common Subnet message Common Subnet Messages Mean T Troubleshooting EIGRP Documentation Having clicked the link for the Troubleshooting EIGRP document shown in the previous slide we arrive here where we have a document that outlines steps of a flowchart for troubleshooting common issues with EIGRP The document starts off by asking you what symptom best describes your problem For example you may respond that the local EIGRP router is not establishing EIGRP neighbors with the neighboring router and then click the command box in red to be taken to the next flowchart as we see in this slide and so on By the way this is one of our interactive documents that offers customized analysis of you
49. ments to rate the solution let us know if it resolved your problem and provide us with any additional feedback 2006 Cisco Systems Inc All rights reserved 79 Presentation_ID scr Recommended Reading EIGRP for IP Basic Operation and Configuration ALVARO RETANA RUSS WHITE DON SLICE com einen Troubleshooting IP Routing Protocols The efinitive ressarce for EGRP design deployment ars cperation EIGRP Network DESIGN SOLUTIONS ASIN 1578701651 ISBN 0201657732 ISBN 1 58705 019 6 e Continue your Networkers at Cisco Live learning experience with further reading for this session from Cisco Press Check the Recommended Reading flyer for suggested books Available Onsite at the Cisco Company Store 2006 Cisco Systems Inc All rights reserved 80 Presentation_ID scr Eee Complete Your Online Session Evaluation Give us your feedback and you could win Don t forget to activate fabulous prizes Winners announced daily your virtual _ account for access to Receive 20 Passport points for each session all session material evaluation you complete on demand and return for our live virtual event Complete your session evaluation online now in October 2008 open a browser through our wireless network Go to the Collaboration to access our portal or visit one of the Internet Zone in World of stations throughout the Convention Center Solutions or visit _ rs Afafe CISCO
50. n interface components of the summary may need to be removed from any neighbors reached through that interface neighbors through that interface are reset to synch up topology entries Route filter changes Similar to summary explanation above neighbors are bounced if a distribute list is added removed changed on an interface in order to synch up topology entries In the past we also bounced neighbors when interface metric info changed delay bandwidth but we no longer do that CSCdp08764 CSCdy20284 was implemented to stop bouncing neighbors when many manual changes occur in late 12 25 12 3T and 12 4 summary and filter changes no longer bounce neighbors Unidirectional Links Operational PVC Broken PVC Hello 1 poe RtrA show ip eigrp neighbors i Updates IP EIGRP neighbors for process 1 RtrA RtrB show ip eigrp neighbors IP EIGRP neighbors for process 1 H Address Interface Hold Uptime SRTT RTO Q Seq sec ms Cnt Num 1 10 1 102 2 Eto 14 00 00 15 0 5000 4 0 2006 Cisco Systems Inc All rights reserved 15 Presentation _ID scr Unidirectional Links In this example we see what happens when a link is only working in one direction unidirectional links can occur because of a duplicate IP address a wedged input queue link errors or any other reason you can think of that would allow packets to be delivered only in one direction on a link The router on the left doesn t even realize t
51. nsmitted up to 16 times if not acknowledged 2006 Cisco Systems Inc All rights reserved 11 Presentation_ID scr Retry Limit Exceeded Exceeding the retry limit means that we re sending reliable packets which are not getting acknowledged by a neighbor When a reliable packet is sent to a neighbor he must respond with a unicast acknowledgement If a router is sending reliable packets and not getting acknowledgements one of two things are probably happening The reliable packet is not being delivered to the neighbor The acknowledgement from the neighbor is not being delivered to the sender of the reliable packet These errors are normally due to problems with delivery of packets either on the link between the routers or in the routers themselves Congestion errors and other problems can all keep unicast packets from being delivered properly Look for queue drops errors etc when the problem occurs and try to ping the unicast address of the neighbor to see if unicasts in general are broken or whether the problem is specific to EIGRP You also see this symptom when a link with separate unidirectional connections is having a problem for example an ATM or Frame Relay link with a PVC working one direction but not the other more on this later Retry Limit Exceeded Reliable packets are re sent after Retransmit Time Out RTO a Typically 6 x Smooth Round Trip Time SRTT Minimum 200 ms Maximum 5000 ms five seconds
52. nterface however then you may want to look into what s happening on the interface Are there errors You can also use this command to see if an interface only contains stub neighbors and if authentication is enabled Other Show Commands Show IP EIGRP Traffic rtrB show ip eigrp traffic IP EIGRP Traffic Statistics for AS 1 Hellos sent received 574 558 Updates sent received 5 7 Queries sent received 2 2 Replies sent received 2 2 Acks sent received 11 7 Input queue high water mark 2 0 drops SIA Queries sent received 1 1 SIA Replies sent received 1 1 Hello Process ID 64 PDM Process ID 63 2006 Cisco Systems Inc All rights reserved 67 Presentation _ID scr Other Show Commands Show IP EIGRP Traffic Show ip eigrp traffic can be very useful to see what kind of activity has been occurring on your network some of the most interesting information include Input queue high water mark this shows how many packets have been queued inside of the router to be processed When packets are received from the IP layer EIGRP accepts the packets and queues them up for processing If the router is so busy that the queue isn t getting serviced the queue could build up Unless there are drops there is nothing to worry about but it can give you an indication of how hard EIGRP is working SIA queries sent received this is useful to determine how often the router has stayed active for at least 1 1 2 minutes
53. ology active IP EIGRP Topology Table for AS 1 ID 10 1 3 1 A 20 1 1 0 24 1 successors FD is Inaccessible Qqr 1 replies active 00 01 52 query origin Successor Origin retries 1 via 10 1 2 1 Infinity Infinity Ethernet0 0 serno 20 via 10 1 3 2 Infinity Infinity q Ethernet1 0 serno 19 anchored 10 1 3 0 24 rtrC C Is Still Waiting on D a Chasing Active Routes Step 4 Hmmm RTRC still thinks the route is active and it s gotten even older There appears to be a problem Houston RTRC thinks he needs a reply from RTRD yet RTRD isn t active on the route we need to take a look at the neighbor relationship between these two routers to try to identify what is going wrong 2006 Cisco Systems Inc All rights reserved 35 Presentation_ID scr Chasing Active Routes Step 5 Let s See Why They Don t Seem to Agree About the Active Route 20 1 1 0 24 rtrC show ip eigrp neighbors IP EIGRP neighbors for process 1 H Address Interface Hold Uptime SRTT RTO Q Seq sec ms Cnt Num 0 10 1 3 2 Et1 0 13 00 00 14 0 5000 0 a 1 10 1 2 1 Eto 0 13 01 22 54 227 1362 385 Looks Like Something s Broken Between Rtrc and Rtrd Chasing Active Routes Step 5 It appears that RTRC is having a bit of a problem communicating with RTRD The neighbor relationship isn t even making it completely up based on the Q count on RTRC We also notice in the log that the neighbor keeps bouncing
54. ork connectivity NAT PBR HSRP and error messages Routing protocols by TAC eng ineers covered include EIGRP OSPF BGP and RIP LAN Switching Configuration connecthtty VLANs trunking autonegotiation passwords and catalyst hardware issues TAC Case Collection The TAC Case Collection is an evolution of the troubleshooting assistant tool and has been enhanced to include new knowledge bases including for IP routing protocols we ll be looking at an EIGRP example today The tool enables you to interactively identify and troubleshoot common problems involving hardware configuration and performance issues These solutions provided directly by TAC engineers have resolved actual networking problems You d select a technology or product area in which you are experiencing a problem or have a question in order to begin the troubleshooting process If you would like to view a short video on demand about how to use the TAC Case Collection please click the link on the tool s launch page This tool offers four different methods of searching for solutions Free text query allows you to interact with the application through natural language This method will be the focus of our coverage of the tool today Guided search allows you to perform a step by step search by answering a series of questions that lead to the most relevant solutions based on the symptoms selected Search by solution in instances where the solution numbe
55. ould have a hard time sorting through it for the pieces you care about the two modifier commands above allow you to limit what the debug output will show Debug ip eigrp AS lt network gt lt mask gt will limit the output to only those entries that pertain to the route identified Debug ip eigrp neighbor AS address will limit the output to those entries pertaining to a particular neighbor Unfortunately you have to enable the debug packet or route events prior to putting the modifier on so you could kill your router before you are able to get the limits placed on the output sorry but that s the way it is Examples of route events with modifiers will be in the next few slides Debugs Debug IP EIGRP Route Events RTRA debug ip eigrp P EIGRP Route Events debugging is on RTRA debug ip eigrp neighbor 1 10 1 6 2 P Neighbor target enabled on AS 1 for 10 1 6 2 P EIGRP Neighbor Target Events debugging is on RTRA Clear ip eigrp neighbor RTRA P EIGRP 10 1 8 0 24 do advertise out Seriall 2 P EIGRP Int 10 1 8 0 24 metric 28160 256002560 P EIGRP 10 1 7 0 24 do advertise out Seriall 2 P EIGRP 10 1 1 0 24 do advertise out Seriall 2 P EIGRP Int 10 1 1 0 24 metric 28160 25600256 P EIGRP Processing incoming UPDATE packet P EIGRP 10 1 6 0 24 do advertise out Seriall 1 2006 Cisco Systems Inc All rights reserved Presentation_ID scr Debugs Debug IP EIGRP Route Events In this debug we are looking at
56. r The Active Process Router C is filtering 10 1 1 0 24 10 1 1 0 24 towards D Router A loses its connection to 10 1 1 0 24 Router A sends C a query Router C has no FS for 10 1 1 0 24 Router C sends D a query Router D examines its local tables No information about 10 1 1 0 24 so send a reply Query is bounded because D has no information about 10 1 1 0 24 No Knowledge of Route so Reply The Active Process Another place where a query will stop being propagated is where the router receiving the query doesn t know anything at all about the prefix In the example above router C is using a distribution list to block the sending of 10 1 1 0 24 to router D when C receives the query from A and doesn t have a feasible path C will send a query to D D looks in his topology table and doesn t find any entries for 10 1 1 0 24 at all because he doesn t know anything about the prefix D immediately sends a reply with an infinity metric unreachable to C notifying him that the prefix is not reachable through him C can then reply to A that the prefix is not reachable through him either since the only reply he received declared the prefix unreachable 2006 Cisco Systems Inc All rights reserved 22 Presentation_ID scr The Active Process Router E is summarizing 10 1 1 0 24 towards F Router A loses its connection to 10 1 1 0 24 Router A sends E a query Router E has no FS for 10 1 1 0 2
57. r Cisco device so if you have the output of a show interface serial show ip eigrp neighbor show tech support or a show ip eigrp topology x x x x command from your Cisco device you can use the Output Interpreter tool to display potential issues and fixes To use the Output Interpreter you must be a registered customer be logged in and have JavaScript enabled And speaking of useful technical support website tools why don t we take a look at one of our most popular ones the TAC Case Collection in order to troubleshoot an EIGRP issue 2006 Cisco Systems Inc All rights reserved 73 Presentation _ID scr TAC Case Collection Free text query Guided search Search by solution number ET TOOLS S UTIUITIES i j The TAC Case Collection an evolution of the Troubleshooting Assistant tool helps you V lew al SO U t 10 ns interactively identify a troubleshoot common problems involving hardware j configuration and performance issues These solutions provided directty by TAC engineers have resolved actual networking problems Please select a technology or a Suggests solutions product area frorn the list below to begin troubleshooting To view a short video on demand on how to use the TAC Case Collection click here that come from actual 4 Common issues on configuration routes missing fom rouling table route not being service requests taken gid nehon OI being sverige neighbor often or Tapping art gt and netw
58. r is known for example if you have been provided the URL to the tool along with a solution number by a TAC engineer you d simply type the solution number in the free text field and be provided directly with the details of that solution these solution numbers begin with the letter K followed by a series of numeric digits View all solutions will link you to a list of all the solution titles in the solution base hyperlinked to their respective solution details page and categorized by problem type So guided search search by solution and view all solutions would yield the same solutions via those other routes as via free text query invite you to check out these three methods on your own A quick note on the tool due to the dynamic nature of the application the supported browser versions are IE 5 5 and above or Netscape 6 x Also please note that you must use the controls and navigation provided within the tool If you use your browser s navigation controls for example the back button search data may be lost 2006 Cisco Systems Inc All rights reserved Presentation_ID scr TAC Case Collection Free Text Query MiBe Close Window T FREE TEXT QUERY En CH VIEW ALL SOLUTIONS X Knowledge Basd P rowing Note Due to the dynamic nature of content within the TAC Case Collection please use the controls and navigation provided within the tool Using the browser s Back button will result in lost data Free Text Qu
59. re listed The entry for each next hop includes the IP address the computed distance through this neighbor the reported distance this neighbor told us and which interface is used to reach him As you can see 10 1 2 2 is a feasible successor because his reported distance 21514560 is less than our current feasible distance 21026560 remember the feasibility condition 2006 Cisco Systems Inc All rights reserved 61 Presentation_ID scr Topology Table Show IP EIGRP Topology All Links Show ip eigrp topology all links displays a list of all neighbors who are providing EIGRP with an alternative path to each destination 10 200 1 0 RtrA show ip eigrp topology all links IP EIGRP Topology Table for AS 1 ID 10 1 6 1 ie SOTO si P 10 200 1 0 24 1 successors FD is 21026560 via 10 1 1 2 21026560 20514560 Serial1 0 Successor via 10 1 2 2 46740736 20514560 Seriall 1 Feasible Successor via 10 1 3 2 46740736 46228736 Seriall 2 Possible Successor f RD Topology Table Show IP EIGRP Topology All Links If you want to display all of the information which EIGRP contains in its topology table use the show ip eigrp topology all links command You ll notice in the above output that not only are the successor 10 1 1 2 and feasible successor 10 1 2 2 shown but another router that doesn t qualify as either is also displayed the reported distance from 10 1 3 2 46228736 is far worse than the cur
60. rent feasible distance 21026560 so he isn t feasible This command is often useful to understand the true complexity of network convergence I ve been on networks with pages of non feasible alternative paths in the topology table because of a lack of summarization distribution lists These large numbers of alternative paths can cause EIGRP to work extremely hard when transitions occur and can actually keep EIGRP from successfully converging 2006 Cisco Systems Inc All rights reserved 62 Presentation_ID scr Topology Table Show IP EIGRP Topology Network Show ip eigrp topology lt network gt lt mask gt displays detailed information for all paths received for that destination 10 200 1 0 RtrA show ip eigrp topology 10 200 1 0 255 255 255 0 IP EIGRP topology entry for 10 200 1 0 24 State is Passive Query origin flag is 1 1 Successor s FD is 21026560 Routing Descriptor Blocks 10 1 1 2 Serial1 0 from 10 1 1 2 Send flag is 0x0 Composite metric is 21026560 20514560 Route is Internal Vector metric 10 1 2 2 Seriall 1 from 10 1 2 2 Send flag is 0x0 Composite metric is 46740736 20514560 Route is Internal Vector metric 10 1 3 2 Seriall 2 from 10 1 3 2 Send flag is 0x0 Composite metric is 46740736 46228736 Route is Internal Vector metric Topology Table Show IP EIGRP Topology Network f you really want to know all of the information EIGRP stores about a particular route use the command show
61. s much much safer just display it and see what s been happening lately Event Log Always running unless manually disabled Default 500 lines configurable EIGRP event log size lt number of lines gt Most recent events at top of log Read bottom to top 2006 Cisco Systems Inc All rights reserved 50 Presentation_ID scr EEE Event Log Separate event log is kept for each AS 500 lines are not very much On a network where there is significant instability or activity 500 lines may only be a second or two or less You can change the size of the event log if needed by the command igrp event log size is the number of lines If number of lines set to 0 it disables the log You can clear the event log by typing clear ip eigrp event Most recent at the top of the log so time flows from bottom to top I Event Log Three Different Event Types Can Be Logged EIGRP log event type dual xmit transport Default is dual normally most useful Any combination of the three can be on at the same time Work in progress to add additional debug info to event log 2006 Cisco Systems Inc All rights reserved 51 Presentation _ID scr EEE Event Log RtrA show ip eigrp events Event information for AS 1 1 01 52 51 223 NDB delete 30 1 1 0 24 1 2 01 52 51 223 RDB delete 30 1 1 0 24 10 1 3 2 a 01 52 51 191 Metric set 30 1 1 0 24 4294967295 4 01 52 51 191 Poi
62. sions sent 0 Out of sequence rcvd 0 Authentication mode is not set Et1 0 1 0 0 885 0 10 6480 0 Hello interval is 5 sec Next xmit serial lt none gt Un reliable mcasts 0 2 Un reliable ucasts 5 3 Mcast exceptions 0 CR packets 0 ACKs suppressed 0 Retransmissions sent 0 Out of sequence rcvd 0 Authentication mode is not set 2006 Cisco Systems Inc All rights reserved Presentation_ID scr Other Show Commands Show IP EIGRP Interface Detail There is also a show ip eigrp interface which contains a subset of this info You may want to just use that if you don t need all the detail This command supplies a lot of information about how the interfaces are being used and how well they are obeying some of the interesting information available via this command is Retransmissions sent this shows how many times EIGRP has had to retransmit packets on this interface indicating that it didn t get an ack for a reliable packet having retransmits is not terrible but if this number is a large percentage of packets sent on this interface something is keeping neighbors from receiving and acking reliable packets Out of sequence rcvd this shows how often packets are received out of order which should be a relatively unusual occurrence Again it s nothing to worry about if you get occasional out of order packets since the underlying delivery mechanism is best effort If the number is a large percentage of packets sent on the i
63. son squashed 30 1 1 0 24 lost if 5 01 52 51 191 Poison squashed 30 1 1 0 24 metric chg 6 01 52 51 191 Send reply 30 1 1 0 24 10 1 3 2 7 01 52 51 187 Not active net 1 SH 30 1 1 0 24 1 8 01 52 51 187 FC not sat Dmin met 4294967295 46738176 9 01 52 51 187 Find FS 30 1 1 0 24 46738176 10 01 52 51 187 Rev query met succ met 4294967295 4294967295 LL 01 52 51 187 Rev query dest nh 30 1 1 0 24 10 1 3 2 12 01 52 36 771 Change queue emptied entries 1 13 01 52 36 771 Metric set 30 1 1 0 24 46738176 Debugs Remember debugs can be dangerous Use only in the lab or if advised by the TAC To make a little safer Logging buffered lt size gt No logging console 2006 Cisco Systems Inc All rights reserved Presentation_ID scr Debugs By enabling logging buffered and shutting off the console log you improve your odds of not killing your router when you do a debug still no guarantees We often change the scheduler interval when we do debugs in the TAC as well this command is version dependent so I m not going to give you syntax here Debugs Use Modifiers to Limit Scope of Route Events or Packet Debugs Limit to a particular neighbor debug ip eigrp neighbor AS address Limit to a particular route debug ip eigrp AS network mask 2006 Cisco Systems Inc All rights reserved 53 Presentation_ID scr EEE Debugs Both packet debugs and route event debugs create so much output that you w
64. tive to the minimum possible if you don t eliminate the reasons that they get stuck you haven t fixed the most important part of the problem the next time you get an active route you could again get stuck The direct impact of an active route is small the possible impact of a stuck in active route can be far greater 2006 Cisco Systems Inc All rights reserved 28 Presentation _ID scr Troubleshooting the Active Part of SIAs Determine what is common to routes going active Flapping link s From the same region of the network 32s from dial in Resolve whatever is causing them to go active if possible Troubleshooting the Active Part of SIAs The syslog may tell you which routes are going active causing you to get stuck Since the SIA message reports the route that was stuck it seems rather straight forward to determine which routes are going active This is only partially true Once SIAs are occurring in the network many routes will go active due to the reaction to the SIA You need to determine which routes went active early in the process in order to determine the trigger Additionally you can do show ip eigrp topology active on the network when SIAs are not occurring and see if you regularly catch the same set of routes going active f you are able to determine which routes are regularly going active determine what is common to those routes Are they 32 routes created from PPP This is acommon cause o
65. twork This modifier can be very useful when trying to troubleshoot a single route or representative route Debugs Debug EIGRP Packet RTRA debug eigrp packet ack EIGRP ack packets hello EIGRP hello packets ipxsap EIGRP ipxsap packets probe EIGRP probe packets query EIGRP query packets reply EIGRP reply packets request EIGRP request packets stub EIGRP stub packets retry EIGRP retransmissions terse Display all EIGRP packets except Hellos update EIGRP update packets verbose Display all EIGRP packet 2006 Cisco Systems Inc All rights reserved Presentation_ID scr Debugs Debug EIGRP Packet This debug is used in a variety of problems and circumstances Debug eigrp packet hello is used to troubleshoot neighbor establishment maintenance problems Debug eigrp packet query reply update etc are also often used to try to determine the process occurring when a problem occurs Be careful I ve crashed hung more than one router by doing a debug on a router that was too busy Probably the most commonly used debug eigrp packet option is terse which includes all of the above except hellos an example follows on the next page Debugs Debug EIGRP Packet Terse RtrA debug eigrp packet terse EIGRP Packets debugging is on UPDATE REQUEST QUERY REPLY IPXSAP PROBE ACK STUB EIGRP Sending UPDATE on Serial1 0 nbr 10 1 1 2 AS 1 Flags 0x0 Seq 2831 1329 idbQ 0 0 iidbQ un rely 0 0 peerQ un rely 0 1 serno 1
66. uest or to query an existing service request In addition under Communities and Training you ll find a link Technical Support Training Resources for training information I d also like to point out a new section Security and Advisories and Alerts that contains links to security advisories field notices and so on We re interested today specifically in troubleshooting EIGRP so we d click the link for Technology Support IP Routing EIGRP Verification and Troubleshooting section for EIGRP as we ll see in the next slide 2006 Cisco Systems Inc All rights reserved 71 Presentation_ID scr Troubleshooting Support for EIGRP Known problems doou mented as ed nes bi field notices GATEWAY ROUTING Troubleshooting steps Verification and 112 Troubleshooting e Fi Troubleshooting tools Troubleshooting Support for EIGRP Here we are in the Verification and Troubleshooting section for EIGRP under IP Routing The troubleshooting section contains a sub section for known problems such as field notices There are also sub sections for troubleshooting steps and tools We re going to take a quick look at a document under troubleshooting steps Troubleshooting EIGRP and at one of our useful troubleshooting tools TAC Case Collection using an EIGRP example 2006 Cisco Systems Inc All rights reserved 72 Presentation _ID scr Troubleshooting EIGRP Docu
67. view of the network than RIP for example The place this additional information is stored is in the topology table The topology table contains an entry for every route EIGRP is aware of and includes information about the paths through all neighbors that have reported this route to him When a route is withdrawn by a neighbor EIGRP will look in the topology table to see if there is a feasible successor which is another downstream neighbor that is guaranteed to be loop free If so EIGRP will use that neighbor and never have to go looking Contrary to popular belief the topology table also contains routes which are not feasible these are called possible successors and may be promoted to feasible successors or even successors if the topology of the network were to change The following slides show a few different ways to look at the topology table and give hints on how to evaluate it Topology Table Show IP EIGRP Topology Summary Total Number of Routes in the Local Topology Table Number of Queries This Router Is Waiting on Replies for Internal Data Structures Used to Manage the Topology Table RtrA sh ip eigrp topology sum IP EIGRP Topology Table for AS 200 ID 40 80 0 17 Head serial 1 next serial 1526 IP EIGRP 0 enabled on 12 interfaces neighbors present on 4 interfaces Quiescent interfaces Po3 Po6 Po2 Gi8 5 Interfaces with No Outstanding Packets to Be Sent or Acknowledged 2006 Cisco Systems Inc All rig
68. xample above router A sends a query to router G router G looks in his topology table and doesn t find an alternative path to the destination Since G doesn t have any other routers to send a query to he will reply to A with a metric of infinity unreachable 2006 Cisco Systems Inc All rights reserved 24 Presentation _ID scr The Active Process In summary a Query Is 10 1 1 0 24 Bounded by Local knowledge of an alternate loop free path not learned through the neighbor the query was received from Local Knowledge of an Alternate Path so Reply No local knowledge of the route because of filtering or summarization No more neighbors No Knowledge of to query Route so Reply No Neighbors F so Reply No Knowledge of H Route so Reply The Active Process So in summary no pun intended a query will stop propagating when A router receiving the query has a loop free alternative path and replies with that value A router receiving the query doesn t have the prefix in its topology table no paths at all much less alternative paths A router receiving the query has no other routers to ask The second point is the most important one in the proper design of a scalable stable EIGRP network use information hiding techniques summarization and filtering to minimize the query scope in your network 2006 Cisco Systems Inc All rights reserved 25 Presentation_ID scr The SI
69. y 10 1 1 2 24 mismatch Secondary 192 168 1 2 24 RtrC show ip eigrp neighbors IP EIGRP neighbors for process 1 RtrC 2006 Cisco Systems Inc All rights reserved 16 Presentation_ID scr Primary Secondary Mismatch While secondary addresses are not used as much as they were when routing protocols were not capable of VLSM Variable Length Subnet Masking they are still sometimes used It is very important to make sure that the primary IP addresses match i e are part of the same subnet EIGRP will accept hellos that are sourced from an address that is a member of the secondary subnet in the example above rtrA and rtrB will accept the hello from rtrC since the 192 168 1 3 address falls in the subnet covered by their secondary addresses If the source is from an address that doesn t exist on the interface neighbors will not form in the example above the hellos from rtrA and rtrB will be sourced from 10 1 1 1 and 10 1 1 2 and when rtrC evaluates the received hello it will find that the sources are not on its only subnet on that interface and the hellos will be rejected The Active Process 2006 Cisco Systems Inc All rights reserved Presentation_ID scr The Active Process What happens if there isn t 10 1 1 0 24 a feasible successor when a router loses its path to a destination A loses its route to 10 1 1 0 24 No FS mark route active 10 1 10 24 Gone No FS Query Set a 1 5 minute

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