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Connect modem to s0 interface 1602

We need to implement a modem backup to our frame-relay if it goes down. However we are using 1602 routers with T1-Wics for our frame connection. The only ports available for modems are the console and the serial 0 port which is the 56K DSU/CSU port. Is there any way to configure the serial 0 port to work with an external modem?

New Member

Re: Connect modem to s0 interface 1602

The built-in 56K CSU/DSU is non-removable and not configurable as async transport device for a modem.

It is possible to use the console port for this purpose, but I would HIGHLY recommend that you do not choose this option.

A number of low-priced replacement routers are available that offer an AUX port for this purpose (Cisco1720) or, if you have access to a Cisco 1601 (which are a dime/dozen on Ebay), you can use the following procedure...

Use the following command on your serial 0 interface:

physical-layer async

After you add this line, a new TTY line will be added. You can configure this just like it was an AUX port or a async port on a terminal server.

Use a RS-232 DTE cable to attach the modem. I believe the part is: CAB-232MT= (don't take my word on this, look it up).

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