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internal v.92 modem on ISR (800/1800/1900) for out-of-band remote management (dial-in)


For Out Of Band Management (Dial-in):


This Config allows one to dial-in to the router for out of band mgmt when the main line is down. This cannot be used as a link for internet access.


this sample is from 891-F


use show platform and identify modem port. You can use show line as well.



------------------ show platform ------------------





Assigned Handlers...

  Vect Handler # of Ints Name

  0 05521278 1 CPLD Interrupt

  1 0564BAD4 0 PEB3081 ISDN S/T Transceiver Interrupt

  2 05A7D69C 10 DX MRVL Address Update interrupt

  3 05F8680C 0 V92 Modem Interrupt  <<=======modem port


sample config:



interface Async3

no ip address

encapsulation slip

keepalive 10


line 3

exec-timeout 0 0

login local

modem InOut

transport input all

transport output all

stopbits 1

speed 115200

flowcontrol hardware


Special note: Please note at times you have to use "modem always-on" instead of "modem inout" and "autohangup" in addition to above.


use clear line <#> to clear the session.


following debugs can be used for troubleshooting:


debug modem

debug confmodem


show commands:

show modem version

show modem

show modem summary

show modem call-stats


Perform following to ensure line is good and modem is working fine


clear line 3

telnet 2003  -- any ip address that is showing up/up

atz - hit enter -this will reset modem config

ats0=1 - hit enter-this will tell modem to answer automatically after one ring

atd - enter -if you are local to the router you should hear dialtone

atdt <tel #> -it should dial out.. try to dial ur cell phone


upon reverse telnet into the modem if you get  "no carrier" "no dialtone" then that is L1 issue.


Dial-Out (When using V.92 as a back-up interface for internet access):


Configuring a V.92 Modem Interface 

The Cisco 891 ISR has a V.92 modem backup interface. To configure this interface, perform these steps, beginning in global configuration mode: 


  1. 1. interface type number
  2. 2. ip address ip-address mask
  3. 3. encapsulation ppp
  4. 4. dialer in-band
  5. 5. dialer string dial-string
  6. 6. dialer-group group-number
  7. 7. async mode dedicated
  8. 8. exit