BASIC MULTICAST TROUBLESHOOTING
Contents
1. incorrect path to RP R8 sh ip mroute 224 10 0 1 224 10 0 1 00 17 20 00 02 41 10 10 0 2 flags SJCL Incoming interface Ethernet0 2 RPF nbr 10 0 38 3 Outgoing interface list Ethernet Forward Sparse 00 17 20 00 02 41 R8 show ip rpf 10 10 0 2 RPF information for 10 10 0 2 interface Ethernet0 2 RPF neighbor 10 0 38 3 RPF route mask 10 10 0 2 32 RPF type unicast ospf 1 Doing distance preferred lookups across tables RPF topology ipv4 multicast base originated from ipv4 unicast base CCE POWERING 7 HFXrAcuL EmcE PROBLEM RECEIVER CAN T REGISTER oProblem solved We have all information required to build PIM Join G tree R8 sh mroute 224 10 0 1 224 10 0 1 00 17 20 00 02 41 RP 10 10 0 2 flags SJCL Incoming interface Ethernet 2 RPF nbr 10 0 38 3 Outgoing interface list Ethernet0 0 Forward Sparse 00 17 20 00 02 41 POWERING HPXrAcuL EmcE PROBLEM RECEIVER CAN T REGISTER oWhat if problem exists somewhere on path between LHR and oJust repeat diagnostic procedure on every router on this path POWERING 772 HXrcuL EDGE PROBLEM SOURCE IS NOT REGISTERING AT RP Problem 1 FHR router 1s not receiving nor processing multicast data E FHR RP S con Ea con _ CO UR E0 2 sf 0 2 0 2 e e POWERING IM umow EDGE PROBLEM SOURCE IS N2. G S Source G Group Receiver 1 Receiver 2 MULTICASTS BASICS YOU HAVE TO KNOW o Any Source Multicast ASM e Classic mode of PIM SM e Shared Tree and Source Tree are used For Shared Tree RP s are used o Source Specific Multicast SSM e Only Source Tree is used No RP Multicast groups only within 232 0 0 0 8 IPv4 and FF3x 96 IPv6 subnets o Bidirectional PIM BiDir Shared Tree POWERING HNowWwL_ESoce MULTICASTS BASICS YOU HAVE TO KNOW o G Shared Tree notification e RP 1s a root We know group address but source 1s unknown o S G Source Tree notification e Source of multicast traffic 1s a root We know both source and group address o Incoming Interface Interface towards multicast source Source Tree or RP Shared Tree o OIL Outgoing Interface List e List of interfaces where multicasts are replicated and distributed CCIE POWERING HPXrAcuL EmcE MULTICASTS BASICS YOU HAVE TO KNOW o RP Randezvous Point For Sparse Mode point of reference required to build common multicast tree o FHR First Hop Router First router on the path Responsible for source registration at RP o LHR Last Hop Router Last router on the path closes to the receiver POWERING IM umow EDGE MULTICASTS BASICS YOU HAVE TO KNOW o Reverse Path Forwarding Check e Used to avoid loops while distributing multicasts e Source addres
3. IP Multicast Statistics 3 routes using 1520 bytes of memory 2 groups 0 50 average sources per group Forwarding Counts Pkt Count Pkts per second Avg Pkt Size Kilobits per second Other counts Total RPF failed Other drops OIF null rate limit etc Group 224 10 0 1 Source count 1 Packets forwarded 1 Packets received 1 o RP tree Forwarding 0 0 0 0 Other 152 152 0 Cle POWERING 7 HraOou Egpcrm PROBLEM SOURCE IS NOT REGISTERING AT RP In next step RP builds S G tree to source of multicast traffic FHR RP 0 2 es zd 55 Sc E0 2 E0 2 EO 1 oa 0 0 am e m LHR RECEIVER POWERING IM umow EDGE PROBLEM SOURCE IS NOT REGISTERING AT RP In next step RP builds S G tree to source of multicast traffic source Shared RAC Tree G SUMMARY o Things we have to check Isip multicast routing is present configuration Is PIM enabled on all interfaces participating in multicast forwarding including loopbacks e If we are using PIM SM or PIM BiDir check if RP 1s properly configured and it s address 1s know for every router within network AutoRP BSR Static e Are there any problems with unicast routing e Is RPF requirement fulfilled Is security properly configured ACLs policers multicast boundary BSR boundary TTL etc POWERING 7 HFX
4. and many topology changes 16 not activated on all interfaces NBMA segments o Many tunnels used to transport multicasts Problems with hardware performance o Bad network design and RP placement POWERING 7 HFXrAcuL EmcE TROUBLESHOOTING APPROACH o Debugging from receiver to the source e Problem can affect only group of receivers look for their common attributes Perform full diagnostics on every router on the path CCIE POWERING HPXrAcuL EmcE PROBLEM S G TREE IS NOT CREATING o Problem in multicast routing table mroute on LHR we can only see G entries We do have active source and its sending traffic G path is correct No S G entries in mroute table CCIE POWERING HPXrAcuL EmcE PROBLEM S G TREE IS NOT CREATING Solution e We need a receiver o Source specific multicast SSM tree would not build unless there is at least one receiver for a group o Properly registered receiver is the one that sent PIN Join for multicast group CCIE POWERING HPXrAcuL EmcE PROBLEM DUPLICATED PACKETS Problem Receiver sometimes receive duplicated packets for groups he joined to o Possible causes Traffic sent 1n dense mode gt Router periodically floods data on interfaces time to time f no receivers are registered then multicast traffic 1s pruned unless timer expire e f there are at least two routers on network segment they elect forwarde
5. MP Membership Report gt Registration request 1s not processed by LHR UR O E FHR RP 0 2 e C0 0 es C0 1 es 0 2 0 2 e zo e 08 RECEIVER PROBLEM RECEIVER CAN T REGISTER Possible causes e On L2 path from receiver to source IGMP filtering occurs e Access list on router interface PIM is not enabled on interface where receiver 1s connected R8 sh run int 0 0 Building configuration Current configuration 83 bytes interface Ethernet0 O ip address 10 0 89 8 255 255 255 0 ip ospf 1 area end POWERING HPXrAcuL EmcE PROBLEM RECEIVER CAN T REGISTER Possible causes e PIM is not enabled on interface where receiver is connected EthernetO 0 is up line protocol is up Internet address is 10 0 89 8 24 Broadcast address is 255 255 255 255 Address determined by setup command MTU is 1500 bytes2 Helper address is not set Directed broadcast forwarding is disabled Multicast reserved groups joined 224 0 0 5 224 0 0 6 Outgoing access list is not set Inbound access list is not set R8 sh ip igmp groups IGMP Connected Group Membership Group Address Interface Uptime Expires Last Reporter Group Accounted 224 0 1 40 Ethernet 1 02 13 52 00 02 03 10 0 78 8 PL POWERING T HmMmowL EDGE PROBLEM RECEIVER CAN T REGISTER o Possible causes e PIM is n
6. OT REGISTERING AT RP Problem 1 e FHR router 1s not receiving nor processing multicast data Possible causes e L2 IGMP filtering occurs on path between sender and the router Access list on router interface another point of filtering e PIM 1s not enabled on intertace CCIE POWERING HPXrAcuL EmcE PROBLEM SOURCE IS NOT REGISTERING AT RP Problem 2 e Source registration is not forwarded to RP CV E FHR RP 0 2 EO EO 1 e oW 22 amp 1 UR O E0 2 E0 2 1 Multicast traffic 2 PIM Register EO 1 PROBLEM SOURCE IS NOT REGISTERING AT RP Possible causes FHR router does not know RP for the group FHR router does not know path to RP for the group e FHR router does not know correct neighbour on the path to the RP incorrect path to RP R1l show ip mroute 224 0 1 40 01 07 32 00 02 32 0 0 0 0 flags DCL Incoming interface Null nbr 0 0 0 0 Outgoing interface list Loopback Forward Sparse Dense 01 07 32 00 00 00 Ethernet0 0 Forward Sparse Dense 01 07 31 00 00 00 o POWERING HPXrAcuL EmcE PROBLEM SOURCE IS NOT REGISTERING AT RP Possible causes FHR router does not know RP for the group FHR router does not know path to RP for the group e FHR router does not know correct neighbour on the path to the RP incorrect path to RP R1 show ip mroute 224 10 0 1 count
7. PT M MSDP created entry E Extranet Proxy Join Timer Running A Candidate for MSDP Advertisement URD I Received Source Specific Host Report Multicast Tunnel z MDT data group sender Joined MDT data group y Sending to MDT data group RD 4 Vector v Vector Outgoing interface flags H Hardware switched A Assert winner Timers Uptime Expires Interface state Interface Next Hop or VCD State Flags 224 100 0 1 00 00 33 stopped 10 10 0 1 flags SJCL Incoming interface Ethernet0 2 RPF nbr 10 0 38 3 IE Outgoing interface list Shared Ethernet0 0 Forward Sparse Dense 00 00 32 00 02 56 e lt NC XK 4 10 10 0 1 224 100 0 1 00 00 30 00 02 29 flags LIT Incoming interface Ethernet0 2 RPF nbr 10 0 38 3 Outgoing interface list Ethernet0 0 Forward Sparse Dense 00 00 30 00 02 56 54 Source Tree POWERING 7 HKMOWL EOCE BASIC COMMANDS R8 sh ip igmp interface Ethernet0 is up line protocol is up Internet address is 10 0 89 8 24 IGMP is enabled on interface Current IGMP host version is 2 Current IGMP router version is 2 IGMP query interval is 6 seconds IGMP configured query interval is 66 seconds IGMP querier timeout 15 120 seconds IGMP configured querier timeout is 120 seconds IGMP max query response time is 16 seconds Last member query count is 2 Last member query response interval is 1000 ms Inbound IGMP access group is not set IGMP acti
8. Possible causes 1 e PIM Join 1s not transmitted by router no knowledge where RP is located R8 sh ip rp mapping 224 10 0 1 PIM Group to RP Mappings Group s 224 0 0 0 4 RP 10 10 0 1 v2 Info source 10 10 0 1 via bootstrap priority 0 holdtime 150 Uptime 03 49 01 expires 00 02 03 POWERING IM umow EDGE PROBLEM RECEIVER CAN T REGISTER Possible causes 1 e PIM Join 1s not transmitted by router no knowledge where RP is located e How router can know RP address o Auto RP o BSR o Static CCIE POWERING HPXrAcuL EmcE PROBLEM RECEIVER CAN T REGISTER o Possible causes 2 Router can t send PIM Join no path to RP R8 show ip mroute 224 10 0 1 00 33 17 00 02 36 RP 192 168 2 2 flags SJCL Incoming interface Null nbr 0 0 0 0 Outgoing interface list Ethernet0 0 Forward Sparse 00 33 17 00 02 36 R8 show ip rpf 192 168 2 2 failed no route exists R8 show ip route 192 168 2 2 Network not in table PROBLEM RECEIVER CAN T REGISTER Possible causes 3 Router can t send PIM Join incorrect path to RP R8 show ip pim rp mapping 224 10 0 1 IP address of RP is known PIM Group to RP Mappings Group s 224 0 0 0 4 RP 10 10 0 1 v2 Info source 10 10 0 1 via bootstrap priority holdtime 150 Uptime 04 13 05 expires 00 02 06 We know the path to RP R8 sh ip route 10 10 0 1 Routing entry for 10 10 0 1 32 Known vi
9. a ospf 1 distance 110 metric 31 type intra area Last update from 10 0 38 3 on Ethernet0 2 04 13 16 ago Routing Descriptor Blocks 10 0 38 3 from 10 10 0 1 04 13 16 ago via Ethernet 2 Route metric is 31 traffic share count is 1 Cle POWERING 7 HraOou Egpcrm PROBLEM RECEIVER CAN T REGISTER Possible causes 3 Router can t send PIM Join incorrect path to RP D C FHR RP E0 2 e 0 0 e E0 1 es 0 2 e m RECEIVER o POWERING IM umow EDGE L g LHR PROBLEM RECEIVER CAN T REGISTER Possible causes 3 Router can t send PIM Join incorrect path to RP R8 sh mroute 224 10 0 1 PIM don t know where the source of traffic is 224 10 0 1 2d 4h 00 02 22 10 10 0 2 Incoming interface Null RPF nbr 0 0 0 0 Outgoing interface list Ethernet0 0 Forward Sparse 2d04h 00 02 21 PIM don t know his neihghbor for this group o RPF rule 1s not fulfilled POWERING HPXrAcuL EmcE R8 show ip rpf 10 10 0 2 failed no route exists PROBLEM RECEIVER CAN T REGISTER Possible causes 3 gt Router can t send PIM Join incorrect path to RP Where 1s the problem PIM not enabled on interface Asymmetric routing Load balancing POWERING IM umow EDGE PROBLEM RECEIVER CAN T REGISTER Possible causes 3 e Router can t send PIM Join
10. eiver is on every subnet so multicast traffic should be replicated on every network Routers must explicitly declare they do now want to receive multicast traffic for particular group due to no receivers and refresh this request periodically Sparse Mode unidirectional tree is built from defined point in network RP toward receivers that have explicitly declare they want to receive traffic In next stages this tree can be rebuild using source of multicast traffic as a root CCIE POWERING HPXrAcuL EmcE MULTICASTS BASICS YOU HAVE TO KNOW Sparse Dense Mode e Hybrid mode Groups with defined RP use sparse mode All others use dense mode e This mode is required to propagate information of RP if Auto RP technology is used but without Auto RP Listener CCIE POWERING HPXrAcuL EmcE MULTICASTS BASICS YOU HAVE TO KNOW Building multicast tree Shared Tree root of the tree is RP All receivers have to register to RP he manage traffic distribution to receivers Shared Distribution Tree Source 1 Notation G All Sources G Group RP PIM Rendezvous Point Shared Tree Source Tree Receiver 1 Receiver 2 MULTICASTS BASICS YOU HAVE TO KNOW Building multicast tree e Source Tree root of the tree is source for prticular multicast group For each receiver S G pair is created Shortest Path or Source Distribution Tree Source 1 Notation S
11. o BASIC MULTICAST TROUBLESHOOTING o Piotr Wojciechowski CCIE 25543 CL C l Ez OWE i IC kA IC LLIL ABOUT Senior Network Engineer MSO at VeriFone Inc Previously Network Solutions Architect at one of top polish IT integrators o CCIE 25543 Routing amp Switching Blogger http ccieplayground wordpress com o Administrator of CCIE PL board e The biggest Cisco community in Europe e Over 6100 users e 8 admin 7 moderators gt 48 polish CCIEs as members 20 of them actively posting e About 150 new topics per month e About 1000 posts per month o e English section available POWERING HPXrAcuL EmcE AGENDA 1 Multicasts basics you have to know 2 Basic diagnostics Why can t I register 1n multicast network CCIE POWERING HPXrAcuL EmcE MULTICASTS BASICS YOU HAVE TO KNOW Multicasts UDP Traffic e Best effort State of multicast distribution and signalization changes dynamically e Application controlled e Multicast replication gt Both source and receiver have to register CCIE POWERING HPXrAcuL EmcE MULTICASTS BASICS YOU HAVE TO KNOW One source many receivers e Source have unicast A B or C class address e Receiver is unknown destination address 16 from class D CCIE POWERING HPXrAcuL EmcE MULTICASTS BASICS YOU HAVE TO KNOW o Three modes gt Dense Mode we assume that rec
12. ot enabled on interface where receiver is connected R8 conFf t Enter configuration commands one per line End with CNTL Z R8 config int e0 0 R8 config if ip pim sparse mode R8 sh 1 igmp groups IGMP Connected Group Membership Group Address Interface Uptime Expires Last Reporter Group Accounted 224 10 0 1 Ethernet 0 00 00 03 00 02 56 10 0 89 8 224 0 1 40 Ethernet0 1 03 21 35 00 02 23 10 0 78 8 Cle POWERING 7 HraOou Egpcrm PROBLEM RECEIVER REGISTER Problem 2 LHR router 1s receiving registration requests e PIM Join is not transmitted over the network Possible causes 1 e Routers are not forwarding IGMP Membership Report no known RP for the group R8 show pim rp 224 10 0 1 Group 224 10 0 1 RP 10 10 0 1 v2 uptime 03 30 41 expires 00 02 19 R8 show 1 mroute IP Multicast Routing Table 224 10 0 1 00 21 06 00 02 30 RP 10 10 0 1 flags 52 1 Incoming interface Ethernet0 2 nbr 10 0 38 3 Outgoing interface list o Ethernet0O 0 Forward Sparse 00 21 06 00 02 30 POWERING HPXrAcuL EmcE PROBLEM RECEIVER CAN T REGISTER Problem 2 LHR router 1s receiving registration requests PIM Join 1s not transmitted over the network D C FHR RP E0 2 e 0 0 e E0 1 es 0 2 RECEIVER o POWERING 7 HFXrAcuL EmcE e ae LHR PROBLEM RECEIVER CAN T REGISTER
13. r who will replicate traffic on this segment e When the timers expires process of flooding pruning and election are repeated which may cause of duplicated packets being sent over that segment o POWERING HPXrAcuL EmcE PROBLEM DUPLICATED PACKETS Solution e Change dense mode to sparse mode e This may also be caused by hardware problems 1 overloaded line cards ln routers or switches ts up to an application to handle duplicated packets so don t worry to much unless it kills your bandwidth CCIE POWERING HPXrAcuL EmcE PIM SM REGISTRATION PROCESS uno ED 9 RP RSA ee ee 1 Sender start sending data 0 2 2 register source in using PIM Register message E0 2 e e On RP and all routers towards source G and S G entries are created gt LHR RECEIVER CCIE POWERING HPXrAcuL EmcE PIM SM REGISTRATION PROCESS 0 0 1 Receiver send IGMP Membership Report 1 his LAN segment its received by R8 0 0 2 8 send registration to 2 RP using PIM Join message G RECEIVER 3 G entries are created on all router on path to RP PIM SM REGISTRATION PROCESS 1 Traffic is being transmitted using Shared Tree 0 2 e e PROBLEM RECEIVER REGISTER Problem 1 We are sure that receiver sends IG
14. rAcuL EmcE QUESTIONS 9 C C I L OWE i IC ani FI IC LLIL ECE THANK YOU e C CCIEE F L OWE i 1C ani FI IC LLIL ECE
15. s is used as a reference If best route unicast routing table to source is through the interface where the packet was received then 1 should be replicated o If packed 1 received with other interface then 1t should be dropped e If same packet is received through multiple interfaces 1t will be replicated only once CCIE POWERING HPXrAcuL EmcE REVERSE PATH FORWARDING CHECK o Both packets with data data plane as well as some of control packets control plane have to pass RPF rule PIM G Join are always sent using shortest path to RP e BSR RP addresses sent inside of BSR messages e Every multicast packet 1n data plane POWERING HPXrAcuL EmcE REVERSE PATH FORWARDING CHECK Multicast Packet from Source 196 7 25 18 Wrong Interface RPF Fails Unicast Routing Table 204 1 16 0 24 Network Interface 196 7 25 0 24 wermom 80 Packet arrived on wrong interlace therefore packet should be dropped 204 1 16 0 24 REVERSE PATH FORWARDING CHECK gt Correct interface APF succeeds Multicast Packet fram Souroa 195 7 25 178 204 1 16 0 24 Unicast Routing Table Packet arrived on correct interface EEN LE 196 7 26 0 24 0 BASIC COMMANDS R8 show ip mroute IP Multicast Routing Table Flags D Dense S Sparse B Bidir Group s SSM Group C Connected L Local P Pruned RP bit set F Register flag SPT bit set J Join S
16. vity 1 joins leaves Multicast routing is enabled on interface Multicast TTL threshold is Multicast designated router DR 15 10 0 89 8 this system IGMP querying router is 10 0 89 8 this system Multicast groups joined by this system number of users 224 100 0 1 1 Cle POWERING 772 HXrcuL EDGE BASIC COMMANDS R8 show ip igmp groups IGMP Connected Group Membership Group Address Interface Uptime Expires Last Reporter Group Accounted 224 100 0 1 Ethernet e 00 07 19 00 02 56 10 0 89 8 224 0 1 40 Ethernet 1 00 30 09 00 02 47 10 0 78 8 CCE POWERING 7 HFXrAcuL EmcE BASIC COMMANDS R8 sh igmp groups detail Flags L Local U User SG Static Group VG Virtual Group SS Static Source VS Virtual Source Ac Group accounted towards access control limit Interface Etherneto 0 Group 224 100 0 1 Flags L Uptime 00 07 30 Group mode EXCLUDE Expires 00 02 45 Last reporter 10 0 89 8 Source list is empty Interface Ethernet 1 Group 224 0 1 40 Flags L Uptime 00 30 20 Group mode EXCLUDE Expires 00 02 36 Last reporter 10 0 78 8 Source list is empty CCE POWERING 7 HFXrAcuL EmcE SAMPLE NETWORK 0 0 EO 1 e E0 2 E0 2 EO 1 e m LHR RECEIVER C C I _ POWERING HPrac3uL St WHEN WE CAN EXPECT PROBLEMS Many IGP protocols and redistribution between them possible routing asymmetry
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