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New Member

Garbled characters when establishing a aux modem connection on 1720

We have a remote office running a Qwest frame relay circuit on a 1720. The aux port has a USR modem connected to it for out-of-band management. The location is currently down, and we are having difficulty establishing a usable connection to the modem. It actually connects, but then the screen fills with garbled characters. I've checked our settings, and they all appear to be correct. Unfortunately, I cannot access the router any other way, as there is no one there who can do anything more than reboot the equipment. I've seen this before but cannot remember the cause. The device is not accessible via the internal LAN either (does not respond to ICMP). Any assistance or advice on things to check would be appreciated.


New Member

Re: Garbled characters when establishing a aux modem connection

Make sure that you are connecting at 9600 and the aux 0 on the router has a speed 9600 command. It sounds like a connection speed is mismatched.

Hope that helps.

New Member

Re: Garbled characters when establishing a aux modem connection

I only have a hard copy of the config for this router (I just took this position, and network documentation is limited). Under line aux 0:

speed 115200

I cannot change this until access is gained to the router (catch-22).

The strange thing is, the modem was hanging off the console port originally. I'm not sure if this was intentional, or accidental.

New Member

Re: Garbled characters when establishing a aux modem connection

You can change your settings on you machine to connect at 9600. If you machine is connecting a 115200, that is probably the problem because it can't negotiate at a higher speed. Try setting the speed to each of the settings on the client and try to connect.

The router might be set at auto.

Also, you can have the modem off of the Aux or the con port - depends on how it was configured.

See the info below for the configs on both console and Aux on a USR Modem:

USR modem on aux


1) Set dip switches 3 and 8 down, all others up.

2) Connect modem to aux port using rolled (console) cable

and Cisco "modem" adapter.

3) Paste the following at an enable (#) prompt:

config t

modemcap edit usrmodem misc &FS0=1&C1&D3&H1&R2&B1

line aux 0

line aux 0

password 7 11281523371E0D0D


modem InOut

modem autoconfigure discovery

transport preferred none

stopbits 1

speed 9600

flowcontrol hardware

NOTE: You might get errors on the "autoselect" lines.

4) Dial into modem. You should get a router prompt.


1) Type "show line" a couple of times and check

if speed of aux line is consistent. If it

changes, it is not autoconfiguring properly.

This means you do not have physical connectivity

to the modem. Power-cycle the modem, check the

cables, and then do "clear line aux 0".

2) If you get garbage when you dial into it, your

init string is bad. You may need a different

modemcap. Try this one:

modemcap edit usrmodem misc &F1S0=1

3) If you get nothing (not even garbage) when you

dial into it, reload the router.


USR modem on console port


1) Set dip switches to 3,8 down, all others up

2) Connect modem to PC

3) Run hyperterminal and connect to modem at 9600 baud

4) Send init string: at&fs0=1&c1&h0&d2&r2&b1&m4&k0&n6&w

5) Set dip switches to 1,4,8 down, all others up

6) Connect modem to console port with appropriate cable

Good Luck.

New Member

Re: Garbled characters when establishing a aux modem connection

Thanks for your help. We were able to get in to the router, but there were no apparent problems. eth0 showed up, as did ser0 (line and protocol). However, we could not ping to or from the router in any direction.

We were getting an error of "ip routing table limit exceeded". I turned off eigrp and setup a static route, but this did not change anything. We're down to ordering a new router for this location, to see if that resolves it.


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