3-1 Modems | Cisco Field Manual[c] Router Configuration

Internal modems include Modem ISDN Channel Aggregation (MICA) and NextPort SPE digital modems and network module analog modems.
Internal modems can be grouped into pools such that each pool can be used for a different purpose. Users dialing into a pool receive a Dialed Number Identification System (DNIS) number and a guaranteed maximum number of simultaneous connections.
The Call Tracker feature can be used to gather and record detailed statistics about active and disconnected calls. The statistics can be retrieved through the command-line interface, Syslog, or SNMP.
External modems can be used when they are connected to asynchronous lines (console, Aux, or line) on routers and access servers.

Configuration

(Optional) Use internal digital modems.
1. Set the country code for the modems:
```
 (global)  modem   country  {  mica   microcom_hdms  }  country  
```
  -OR-
```
 (global)  spe country   country  
```
  The digital modem type is given as mica (MICA), microcom_hdms (Microcom), or spe (NextPort). The country code must be one of argentina, australia , austria , belgium, brazil, canada, chile, china, columbia , czech-republic, denmark, europe, finland , france, germany , greece, hong-kong, hungary, india, indonesia, israel, italy, japan, korea, malaysia, mexico , netherlands, norway, peru, philippines, poland, portugal, saudi-arabia, singapore , south-africa, spain, sweden, switzerland, taiwan, thailand , united-kingdom, or usa. The MICA and NextPort modems also add country codes: e1-default (default E1, a-Law), russia, t1-default (default T1, u-Law), and turkey .
2. (Optional) Group modems into a logical pool.
  - Create a modem pool:
```
 (global)  modem-pool   pool-name  
```
    By default, all internal modems are members of a system default pool. Grouping modems into a logical or virtual pool allows each pool to be used for different purposes.
  - Define the range of modems in the pool:
```
 (modem-pool)  pool-range   low-high  
```
    The range is defined as low (the lowest numbered modem line), a dash, and high (the highest numbered modem line). To find the modem line numbers , you can use the show modem command.
  - Define one or more DNIS numbers for the pool:
```
 (modem-pool)  called-number   dnis-number  [  max-conn   connections  ] 
```
    When a user dials into an access server, the router uses the DNIS number (the number that was called) to find the appropriate modem pool. Each user accessing the pool can be limited to connections simultaneous connections.
3. (Optional) Use Call Tracker to gather statistics from internal modems.
  
  NOTE
  
  You can view the Call Tracker history from the command line by using the show call calltracker active (active calls) and the show call calltracker history (disconnected calls) commands. To see detailed information about the last call on a specific modem, use the show modem calltracker [ slot/port ] command.
  - Enable Call Tracker:
```
 (global)  calltracker enable  
```
  - Specify the Call Tracker history:
```
 (global)  calltracker history max-size   number  (global)  calltracker history retain-mins   minutes  
```
    The maximum number of call entries that are recorded can be set to number (0 to 10 times the number of DS0 channels supported on the router; the default is 1 times the maximum number of supported DS0s). A value of 0 prevents call entries from being recorded. Call entries can also be retained in memory for minutes (0 to 26000 minutes; the default is 5000). A value of 0 prevents the call history from being saved. When increasing the history size, choose the values carefully so that Call Tracker doesn't consume too much router memory.
  - (Optional) Collect statistics on MICA modems:
```
 (global)  modem link-info poll time   seconds  
```
    Call Tracker can poll MICA modems for statistics at intervals of seconds (10 to 65535 seconds).
  - (SNMP only) Enable the Call Tracker SNMP trap:
```
 (global)  snmp-server enable traps calltracker  
```
    If SNMP is used to gather the Call Tracker history, you must enable the calltracker trap. See Section 1-6 for more information about SNMP and Syslog configuration.
4. (Optional) Busy out or disable modems.
  - Disable a single modem:
```
 (line)  modem bad  
```
    -OR-
```
 (line)  modem shutdown  
```
  You can remove an idle modem from service with the bad keyword. A bad active modem can be abruptly shut down with the shutdown keyword.
  - Use modem recovery to detect and recover from faults.
    
    To detect a faulty modem, enter the following command:
```
 (global)  modem recovery threshold   number  
```
    After number (1 to 1000 attempts; the default is 30 call attempts) attempts are made to use an unresponsive modem, the modem recovery process is started.
    
    To define the amount of time before a modem is considered unresponsive, enter the following command:
```
 (global)  modem recovery-time   minutes  
```
    A modem is considered locked and unresponsive after minutes (the default is 5 minutes) have passed since a call request was made.
    
    To define the type of recovery action to take, enter the following command:
```
 (global)  modem recovery action  {  disable   download   none  } 
```
    When modem recovery enters the maintenance window, it attempts to recover faulty modems. The recovery action can be disable (mark a faulty modem as bad and disable it), download (schedule the modem for a firmware download), or none (don't try to recover a faulty modem; keep using it).
    
    To define the automatic modem recovery process, enter the following command:
```
 (global)  modem recovery maintenance  {  action  {  disable   drop-call   reschedule  }  max-download   number   schedule  {  immediate   pending  }  time   hh:   mm   window   minutes  } 
```
    Every 24 hours, the router performs the modem recovery maintenance process on modems that have been marked as faulty. Faulty modems have their firmware reloaded in an attempt to bootstrap them. All modems on the same module as a faulty modem are first flagged as being in the "recovery pending" state. This prevents some modems with active calls from being reinitialized with a firmware download. The window keyword defines a maintenance window for minutes (the default is 60 minutes); as soon as the window timer expires , the pending modems are recovered.
    
    As soon as the window is expired , an action is taken: disable (mark the faulty modems as bad and return other modems to service), drop-call (drop any active calls and reload the firmware), or reschedule (reschedule the firmware reload until the next maintenance window; this is the default). The maintenance window can be set with the schedule keyword, as immediate (attempt modem recovery now) or pending (wait until the next window 24 hours later; this is the default). The time of day for the regular maintenance window can be set with the time keyword, as hh:mm (a 24- hour time format; the default is 3:00 a.m.).
    
    To prevent a large number of modems from being disabled and reloaded at one time, you can use the max-download keyword to place a limit on the number of modems that will be recovered, as number (1 to 30; the default is 20 percent of the number of modems on a system).
Set modem parameters (internal or external modems).
1. Define a range of lines to use with modems:
```
 (global)  line   start-line end-line  
```
2. Define the connection protocols that can be used over the lines:
```
 (line)  transport  {  input   output  } {  all   none  } 
```
3. (Optional) Automatically start up an async protocol:
```
 (line)  autoselect  {  arap   ppp   slip  } 
```
  When a connection is made to a modem line, one or more of the protocols arap (AppleTalk Remote Access Protocol), ppp, and slip can be started.
4. Select the modem control mode:
```
 (line)  modem  {  dialin   inout  } 
```
  The modem can be configured to allow incoming connections only ( dialin ) or to allow both incoming and outgoing connections ( inout ).
5. Define the modem initialization string.
  - (Optional) Use an existing modem definition.
    
    To see if the router has a preconfigured entry for your modem, enter the following command:
```
 (exec)  show modemcap  [  modem-type  ] 
```
    A list of the preconfigured modem types is shown. As soon as you find a modem type in the list, you can view all the preconfigured attributes for it by adding the modem-type to the command.
    
    To edit a preconfigured modem type if needed, enter the following optional command:
```
 (global)  modemcap edit   modem-name attribute at-command  
```
    The modem-name must be one of the types listed from show modemcap . The attribute is the name of an attribute listed in the show modemcap modem-type command. The at-command is a string of characters that define the "AT-style" modem command you want to use for the attribute.
    
    To apply the modem type to the line, enter the following command:
```
 (line)  modem autoconfigure type   modem-name  
```
    For internal digital modems, the type of modem can be defined as microcom_server (Cisco Microcom V.34/56k on an AS5200), cisco_v110 (Cisco NEC internal V.110 TA on an AS5200), microcom_mimic (Cisco Microcom internal analog modem on an NM-AM), mica (Cisco MICA), nextport (Cisco NextPort CSMV/6), or microcom_hdms (Microcom HDMS chassis).
    
    For external modems, the type of modem can be defined as default (generic Hayes -compatible), codex_3260 (Motorola Codex 3260), usr_courier (US Robotics Courier), usr_sportster (US Robotics Sportster), hayes_optima (Hayes Optima), global_village (Global Village Teleport), viva (Viva Rockwell ACF with MNP), telebit_t3000 (Telebit T3000), nec_v34 (NEC V.34), nec_v110 (NEC V.110 TA), or nec_piafs (NEC PIAFS TA).
    
    The modem initialization string is preconfigured in the IOS software and is reapplied to the modem every time the line goes down. To see a complete list of the preconfigured modem types, use the show modemcap command.
  - (Optional) Automatically discover the modem type:
```
 (line)  modem autoconfigure discovery  
```
    Each time the line goes down, the router sends a string of commands to the modem in an attempt to discover the modem's type. The router can discover only modem types that are already configured ( show modemcap ). If the modem type can't be discovered , the router retries for 10 seconds. To see the results of the discovery, use the show line line command. Be aware that discovery mode is considerably slower than using a modem type that is manually configured.
6. (Optional) Place modem lines into a rotary group:
```
 (line)  rotary   group  
```
  The line is identified with the rotary group numbered group. It becomes part of a hunt group for outgoing calls.
(Optional) Create a chat script for interaction with a modem or remote system.
1. Define the chat script:
```
 (global)  chat-script   script-name expect-send-string  
```
  A chat script is created with the name script-name (text string). You can choose a script name that corresponds to a modem vendor, type, and modulation, as in vendor- type-modulation. When chat scripts are used, the name of the script can be wildcarded so that a matching chat script name will be selected.
  
  The actual chat script consists of an expect-send-string (text string), which consists of pairs of strings. The expect string is expected to be received from the modem or remote system, and the send string is to be sent back in response.
  
  A chat script can contain special escape sequences, as shown in Table 3-1.
  
  Here is a sample chat script:
```
  chat-script DialRemote ABORT ERROR ABORT BUSY ABORT "NO ANSWER" ""   "AT H" OK "ATDT \T" TIMEOUT 45 CONNECT \c  
```
  The script is named DialRemote, and it aborts if either ERROR, BUSY, or " NO ANSWER " is received from the modem. The script expects to see nothing (two double quotes), and then it sends " AT H " to force the modem to go on-hook. As soon as OK is received from the modem, the script sends " ATDT \T " to dial the digit string that is sent in place of the \T characters. The script waits for a maximum timeout of 45 seconds, expecting to see CONNECT from the modem. The \c causes the script to suppress a newline character as the final send string.
2. Use the chat script during a line event:
```
 (line)  script  {  activation   connection   dialer   reset   startup  }  regexp  
```
  A chat script that matches the regexp regular expression is used to communicate with a modem or remote system over the line when the specified line event occurs. Line events can be activation (when the line is activated with a new EXEC session), connection (when a network connection is made on the line), dialer (when DDR triggers an outbound call; used with a modem), reset (when the line is reset), or startup (when the router is started up).

NOTE

If a chat script is not working properly, you can use the debug chat line line-number command to watch the interactive expect-send process.

Table 3-1. Chat Script Escape Sequences

Escape Sequence	Description
\value	Sends the ASCII character that has the value in octal (three digits of 0 to 7).
\\	Sends a backslash (\) character.
\"	Sends a double-quote (") character.
\c	Suppresses a new line at the end of the send string.
\d	Delays for 2 seconds.
\K	Inserts a BREAK.
\n	Sends a newline or linefeed character.
\N	Sends a null character.
\p	Pauses for 0.25 seconds.
\q	Reserved.
\r	Sends a return.
\s	Sends a space character.
\t	Sends a tab character.
\T	\T is replaced by the phone number from a dial string.
""	Expects a null string.
BREAK	Causes a BREAK.
EOT	Sends an end-of-transmission character.
ABORT string	Expects a string and indicates an aborted condition.
TIMEOUT time	Sets the time to wait for an expected input for time seconds (the default is 5).