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New Member

Modem Connection

Hello,

When connecting an external modem to a synchronous serial interface is there any need to configure lines, and if so which lines would I configure as most times external modems would be attached to the AUX port and the corresponding lines are configured. Any help would be appreciated.

Thanks

5 REPLIES
Bronze

Re: Modem Connection

You can only connect a modem to an asynchronous interface (or an async/sync interface).

For an A/S interface you need to configure it as asyn first:

interface serial

physical-layer async

this will add a "line " to your config which you can then configure further.

hth

Herbert

New Member

Re: Modem Connection

Greetings Herbert,

Thanks for your response. Can you still not even if the modem is an external synchronous modem? It seems that one of my other router (same series, same configuration, same modem) is working fine with the modem attached to the serial interface all calls are connected and go through okay, or are they getting through some other way that I am not aware of. Any help is appreciated as this is mind boggling.

Dallas

Bronze

Re: Modem Connection

Sorry, since you mentioned lines I assumed you meant an async modem. Don't have any experience with synchronous modems, I must admit.

So you're saying the other router works fine but this one does not? What are the symptoms?

Herbert

New Member

Re: Modem Connection

Greetings Herbert,

Well the modem is a codex 3260 and it will answer when it is dialed, however it does not seem to be handshaking with the router that it is attached to to let info pass. I am going to issue a debug modem and try and make a call and see where the errors are occuring, I may paste it in here if I cannot locate the problem area. When I issue a show int serial, the line is down, protocol is down no dcd, dtr, etc, and have tried pretty much everything, changing cables, etc. The modem will however work when connected to another router of the same series and similar config so I do know the issue is with the interface. The debug modem output is my last hope to see exactly whats happening. Thanks for your input.

Dallas

Bronze

Re: Modem Connection

Hi Dallas,

I have installed a few sync modems for some of our customers. At first I was worried on how am I going to configure the router with a sync modem connected. I assume you're using a sync dial modem connected to a sync serial interface. What we did was to dial the number using the modem itself. After getting a successful connection, we just configured the serial interface of the router with an IP address. We have tried Cisco's HDLC and PPP as the encapsulation, both are working fine. This may not be exactly the same with your setup but I might be able to offer some help. Please post the debugs here after getting them.

Goodluck!

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