Cisco Systems DC-145 User's Manual
Contents
1. login requests in a queue when lines are busy See the section Configuring Asynchronous Rotary Line Queueing in the Configuring Asynchronous Lines and Interfaces chapter for more information mi Cisco 10S Dial Technologies Configuration Guide _ Configuring and Managing External Modems Step 1 Step 2 Step 3 Step 4 Managing Telnet Sessions W Suspending Telnet Sessions When you are connected to an external modem the direct Telnet session must be terminated before the line can accept incoming calls If you do not terminate the session it will be indicated in the output of the show users command and will return a modem state of ready if the line is still in use If the line is no longer in use the output of the show line value command will return a state of idle Terminating the Telnet session requires first suspending it then disconnecting it To suspend a Telnet session perform the following steps Enter Ctrl Shift 6 x to suspend the Telnet session suspend keystroke Router amp Note Ensure that you can reliably issue the escape sequence to suspend a Telnet session Some terminal emulation packages have difficulty sending the Ctrl Shift 6 x sequence Refer to your terminal emulation documentation for more information about escape sequences Enter the where EXEC command to check the connection numbers of open sessions Router where Conn Host Address Byte Idle Conn Name so 1 AGS2. reverse Telnet Performing a reverse Telnet means that you are initiating a Telnet session out the asynchronous line instead of accepting a connection into the line called a forward connection Note Before attempting to allow inbound connections make sure that you close all open connections to the modems attached to the access server If you have a modem port in use the modem will not accept a call properly To establish a direct Telnet session to an external modem determine the IP address of your LAN Ethernet interface and then enter a Telnet command to port 2000 n on the access server where n is the line number to which the modem is connected For example to connect to the modem attached to line 1 enter the following command from an EXEC session on the access server Router telnet 172 16 1 10 2001 Trying 172 16 1 10 2001 Open This example enables you to communicate with the modem on line 1 using the AT attention command set defined by the modem vendor Timesaver Use the ip host configuration command to simplify direct Telnet sessions with modems The ip host command maps an IP address of a port to a device name For example the modem1 2001 172 16 1 10 command enables you to enter modem1 to initiate a connection with the modem instead of repeatedly entering telnet 172 16 1 10 2001 each time you want to communicate with the modem You can also configure asynchronous rotary line queueing which places Telnet
3. the speed of the port on the access server is changed you must establish a direct Telnet session to the modem and send an at command so that the modem can learn the new speed Cisco 10S Dial Technologies Configuration Guide DC 148 _ Configuring and Managing External Modems Supporting Dial InModems W Modems differ in the method that they use to lock the E A TIA 232 serial port speed In the modem documentation vendors use terms such as port rate adjust speed conversion or buffered mode Enabling error correction often puts the modem in the buffered mode Refer to your modem documentation to learn how your modem locks speed check the settings amp b j amp q n or s register settings RTS and CTS signals must be used between the modem and the access server to control the flow of data Incorrectly configuring flow control for software or setting no flow control can result in hung sessions and loss of data Modems differ in the method that they use to enable hardware flow control Refer to your modem documentation to learn how to enable hardware flow control check the settings amp e amp k amp h amp r or s register The modem must use the DCD wire to indicate to the access server when a session has been negotiated and is established with a remote modem Most modems use the setting amp c1 Refer to your modem documentation for the DCD settings used with your modem The modem must interpret a toggle of the DTR signal a
4. Configuring and Managing External Modems Checking Other Modem Settings W Checking Other Modem Settings This section defines other settings that might be needed or desirable depending on your modem Error correction can be negotiated between two modems to ensure a reliable data link Error correction standards include Link Access Procedure for Modems LAPM and MNP4 V 42 error correction allows either LAPM or MNP4 error correction to be negotiated Modems differ in the way they enable error correction Refer to your modem documentation for the error correction methods used with your modem Data compression can be negotiated between two modems to allow for greater data throughput Data com pression standards include V 42bis and MNP5 Modems differ in the way they enable data compression Refer to your modem documentation for the data compression settings used with your modem Cisco 10S Dial Technologies Configuration Guide B 0c 155 Configuring and Managing External Modems HI Checking Other Modem Settings Cisco 10S Dial Technologies Configuration Guide
5. Configuring and Managing External Modems This chapter describes how to configure externally connected modems These tasks are presented in the following main sections e External Modems on Low End Access Servers e Automatically Configuring an External Modem e Manually Configuring an External Modem e Supporting Dial In Modems e Testing the Modem Connection e Managing Telnet Sessions e Modem Troubleshooting Tips e Checking Other Modem Settings To identify the hardware platform or software image information associated with a feature use the Feature Navigator on Cisco com to search for information about the feature or refer to the software release notes for a specific release For more information see the Identifying Supported Platforms section in the Using Cisco IOS Software chapter For a complete description of the modem support commands in this chapter refer to the Cisco IOS Dial Technologies Command Reference To locate documentation of other commands that appear in this chapter use the command reference master index or search online External Modems on Low End Access Servers Some of the Cisco lower end access servers such as the Cisco AS2511 RJ shown in Figure 23 have cable connections to external modems The asynchronous interfaces and lines are inside the access server Cisco 10S Dial Technologies Configuration Guide Bm 0c 145 Configuring and Managing External Modems W Automatically Configuring
6. aging External Modems Testing the Modem Connection Hi Testing the Modem Connection Step 1 Step 2 Step 3 To test the connection send the modem the AT command to request its attention The modem should respond with OK For example at OK If the modem does not reply to the at command perform the following steps Enter the show users EXEC command and scan the display output The output should not indicate that the line is in use Also verify that the line is configured for modem inout Enter the show line EXEC command The output should contain the following two lines Modem state Idle Modem hardware state CTS noDSR DTR RTS If the output displays no CTS for the modem hardware state the modem is not connected is not powered up is waiting for data or might not be configured for hardware flow control Verify the line speed and modem transmission rate Make sure that the line speed on the access server matches the transmission rate as shown in Table 13 Table 13 Matching Line Speed with Transmission Rate Modem Transmission Rate Line Speed on the Access Server in bits per second in bits per second 9600 38400 14400 57600 28800 115200 To verify the line speed use the show run EXEC command The line configuration fragment appears at the tail end of the output The following example shows that lines 7 through 9 are transmitting at 115200 bits per second bps Sixteen 28800 kbps
7. an External Modem Figure 23 Cisco AS2511 RJ Access Server Cisco AS2511 RJ SESS Sesssoses GO 2 E o NSOLE AUX cor 000000000 X Modems are outside peer the chassis 14479 When you configure modems to function with your access server you must provide initialization strings and other settings on the modem to tell it how to function with the access server This section assumes that you have already physically attached the modem to the access server If not refer to the user guide or installation and configuration guide for your access server for information about attaching modems Automatically Configuring an External Modem The Cisco IOS software can issue initialization strings automatically in a file called a modemcap for most types of modems externally attached to the access server A modemcap is a series of parameter settings that are sent to your modem to configure it to interact with the Cisco device in a specified way The Cisco IOS software defines modemcaps that have been found to properly initialize most modems so that they function properly with Cisco routers and access servers For Cisco IOS Release 12 2 these modemcaps have the following names e default Generic Hayes interface external modem e codex_3260 Motoro
8. bo 80 Dar cred BY Sig re 0 O 172 16 1 10 2 AIS 6 LTI 17216 111 0 12 modem2 When you have suspended a session with one modem you can connect to another modem and suspend it Router telnet modem2 Trying modem2 172 16 1 11 2002 Open suspend keystroke Router To disconnect completely close a Telnet session enter the disconnect EXEC command Router disconnect line 1 Closing connection to 172 16 1 10 confirm y Router disconnect line 2 Closing connection to 172 16 1 11 confirm y Router Cisco 10S Dial Technologies Configuration Guide Configuring and Managing External Modems W Modem Troubleshooting Tips Modem Troubleshooting Tips Table 14 contains troubleshooting tips on modem access and control Table 14 Modem Troubleshooting Tips Problem Likely Cause Connection refused Someone already has a connection to that port or an EXEC is running on that port or The modem failed to lower the carrier detect CD signal after a call disconnected resulting in an EXEC that remained active after disconnect To force the line back into an idle state clear the line from the console and try again If it still fails ensure that you have set modem inout command for that line If you don t have modem control either turn off EXEC on the line by using the exec timeout line configuration command before making a reverse connection or configure the modem using an external terminal As a last reso
9. e current and stored configuration of the modem that you are using Generally you enter at commands such as amp v i4 or o to view inspect or observe the settings You must first create a direct Telnet or connection session to the modem before you can send an initialization string You can use AT amp F as a basic modem initialization string in most cases To establish a direct Telnet session to an external modem determine the IP address of your LAN Ethernet interface and then enter a Telnet command to port 2000 n on the access server where n is the line number to which the modem is connected See the sections Testing the Modem Connection and Managing Telnet Sessions for more information about making Telnet connections A sample modem initialization string for a US Robotics Courier modem is as follows amp b1 amp h1 amp r2 amp c1 amp d3 amp m4 amp k1s0 1 Modem initialization strings enable the following functions e Locks the speed of the modem to the speed of the serial port on the access server e Sets hardware flow control RTS CTS or request to send clear to send e Ensures correct data carrier detect DCD operation e Ensures proper data terminal ready DTR interpretation e Answers calls on the first ring Note Make sure to turn off automatic baud rate detection because the modem speeds must be set to a fixed value The port speed must not change when a session is negotiated with a remote modem If
10. hnologies Configuration Guide gy Configuring and Managing External Modems W Supporting Dial In Modems Figure 24 EXEC Creation on a Line Configured for Modem Dial In Idle state DTR low watching oe CTS Ee 4 I I I I 1 i I l I l Lower DTR 1 i i I l I I f I I l I I I Answer timeout SY SS DTR high Hang up DTR low lt watching Ringing CTS I I I I I I i Lower DTR i close connection CTS raised I I I I I I 1 I 1 I 1 CTS lowered 1 Create EXEC or exit N DTR high 7 1 N 1001a i Ready and active Note The modem callin and modem cts required line configuration commands are useful for SLIP operation These commands ensure that when the line is hung up or the CTS signal drops the line reverts from Serial Line Internet Protocol SLIP mode to normal interactive mode These commands do not work if you put the line in network mode permanently Although you can use the modem callin line configuration command with newer modems the modem dialin line configuration command described in this section is more appropriate The modem dialin command frees up CTS input for hardware flow control Modern modems do not require the assertion of DTR to answer a phone line that is to take the line off hook E Cisco 10S Dial Technologies Configuration Guide _ Configuring and Man
11. la Codex 3260 external e usr_courier U S Robotics Courier external e usr_sportster U S Robotics Sportster external e hayes_optima Hayes Optima external e global_village Global Village Teleport external e viva Viva Rockwell ACF with MNP external e telebit_t3000 Telebit T3000 external e nec_v34 NEC V 34 external e nec_v110 NEC V 110 TA external e nec_piafs NEC PIAFS TA external The hayes_optima modemcap is not recommended for use instead use the default modemcap Cisco 10S Dial Technologies Configuration Guide _ Configuring and Managing External Modems Step 1 Step 2 Automatically Configuring an External Modem W Enter these modemcap names with the modemcap entry command If your modem is not on this list and if you know what modem initialization string you need to use with it you can create your own modemcap see the following procedure Using the Modem Autoconfigure Type Modemcap Feature To have the Cisco IOS software determine what type of modem you have use the modem autoconfigure discovery command to configure it as described in the procedure Using the Modem Autoconfigure Discovery Feature Using the Modem Autoconfigure Type Modemcap Feature Use the modemcap edit command to define your own modemcap entry The following example defines modemcap MODEMCAPNAME Router config modemcap edit MODEMCAPNAME miscellaneous amp FS0 1 amp D3 Apply the modemcap to the modem lines a
12. modems are connected to a Cisco AS2511 RJ access server via a modem cable Router show run Building configuration Current configuration I line 1 16 login local modem InOut speed 115200 transport input all flowcontrol hardware script callback callback autoselect ppp autoselect during login Cisco 10S Dial Technologies Configuration Guide gy Configuring and Managing External Modems W Managing Telnet Sessions Step 4 Step 5 The speeds of the modem and the access server are likely to be different If so switch off the modem and then switch it back on This action should change the speed of the modem to match the speed of the access server Check your cabling and the modem configuration echo or result codes might be off Enter the appropriate at modem command to view the modem configuration or use the at amp f command to return to factory defaults Refer to your modem documentation to learn the appropriate at command to view your modem configuration Note See the section Configuring Cisco Integrated Modems Using Modem Attention Commands in the Configuring and Managing Integrated Modems chapter for information about modem attention commands for the Cisco internal modems Managing Telnet Sessions You communicate with an external modem by establishing a direct Telnet session from the asynchronous line on the access server which is connected to the modem This process is also referred to as
13. rt disconnect the modem clear the line make the Telnet connection and then attach the modem The prevents a misconfigured modem from denying you line access Connection appears to hang Try entering U clear line Q XON and press Return a few times to try to establish terminal control EXEC does not come up autoselect is on Press Return to enter EXEC Modem does not hang up after entering quit The modem is not receiving DTR information or you have not set up modem control on the router Interrupts another user session when you dial in The modem is not dropping CD on disconnect or you have not set up modem control on the router Connection hangs after entering on the The answering modem saw and interpreted the when it was echoed dialing modem followed by an ATO to you This is a bug in the answering modem common to many modems There may be a switch to work around this problem check the modem s documentation Losing data You may have Hardware Flow Control only on for either the router s line DTE or the modem DCE Hardware Flow Control should be on for both or off for both but not for only one Using MDCE Turn MDCE into an MMOD by moving pin 6 to pin 8 because most modems use CD and not DSR to indicate the presence of carrier You can also program some modems to provide carrier info via DSR mi Cisco 10S Dial Technologies Configuration Guide _
14. s a command to drop any active call and return to the stored settings Most modems use the settings amp d2 or amp d3 Refer to your modem documentation for the DTR settings used with your modem If a modem is used to service incoming calls it must be configured to answer a call after a specific number of rings Most modems use the setting s0 1 to answer the call after one ring Refer to your modem documentation for the settings used with your modem Supporting Dial In Modems Command The Cisco IOS software supports dial in modems that use DTR to control the off hook status of the telephone line This feature is supported primarily on old style modems especially those in Europe To configure the line to support this feature use the following command in line configuration mode Purpose Router config line modem callin Configures a line for a dial in modem Figure 24 illustrates the modem callin command When a modem dialing line is idle it has its DTR signal at a low state and waits for a transition to occur on the data set ready DSR input This transition causes the line to raise the DTR signal and start watching the CTS signal from the modem After the modem raises CTS the Cisco IOS software creates an EXEC session on the line If the timeout interval set with the modem answer timeout command passes before the modem raises the CTS signal the line lowers the DTR signal and returns to the idle state Cisco 10S Dial Tec
15. s shown in the following example Router terminal monitor Router debug confmodem Modem Configuration Database debugging is on Router configure terminal Enter configuration commands one per line End with CNTL Z Router config line 33 34 Router config line modem autoconfigure type MODEMCAPNAME Router config line Jan 16 18 12 59 643 TTY34 detection speed 115200 response OK Jan 16 18 12 59 643 TTY34 Modem command AT amp FS0 1 amp D3 Jan 16 18 12 59 659 TTY33 detection speed 115200 response OK Jan 16 18 12 59 659 TTY33 Modem command AT amp FS0 1 amp D3 Jan 16 18 13 00 227 TTY34 Modem configuration succeeded Jan 16 18 13 00 227 TTY34 Detected modem speed 115200 Jan 16 18 13 00 227 TTY34 Done with modem configuration Jan 16 18 13 00 259 TTY33 Modem configuration succeeded Jan 16 18 13 00 259 TTY33 Detected modem speed 115200 Jan 16 18 13 00 259 TTY33 Done with modem configuration Using the Modem Autoconfigure Discovery Feature If you prefer the modem software to use its autoconfigure mechanism to configure the modem use the modem autoconfigure discovery command The following example shows how to configure modem autoconfigure discovery mode Router terminal monitor Router debug confmodem Modem Configuration Database debugging is on Router configure terminal Enter configuration commands one per line End with CNTL Z Router config line 33 34 Rou
16. ter config line modem autoconfigure discovery Jan 16 18 16 17 724 TTY33 detection speed 115200 response OK Jan 16 18 16 17 724 TTY33 Modem type is default Jan 16 18 16 17 724 TTY33 Modem command AT amp F amp C1 amp D2S0 1H0 Jan 16 18 16 17 728 TTY34 detection speed 115200 response OK Jan 16 18 16 17 728 TTY34 Modem type is default Jan 16 18 16 17 728 TTY34 Modem command AT amp F amp C1 amp D2S0 1H0 Jan 16 18 16 18 324 TTY33 Modem configuration succeeded Cisco 10S Dial Technologies Configuration Guide gy Configuring and Managing External Modems W Manually Configuring an External Modem Jan 16 18 16 18 324 TTY33 Detected modem speed 115200 Jan 16 18 16 18 324 TTY33 Done with modem configuration Jan 16 18 16 18 324 TTY34 Modem configuration succeeded Jan 16 18 16 18 324 TTY34 Detected modem speed 115200 Jan 16 18 16 18 324 TTY34 Done with modem configuration Manually Configuring an External Modem Timesaver If you cannot configure your modem automatically you must configure it manually This section describes how to determine and issue the correct initialization string for your modem and how to configure your modem with it Modem command sets vary widely Although most modems use the Hayes command set prefixing commands with at Hayes compatible modems do not use identical at command sets Refer to the documentation that came with your modem to learn how to examine th
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