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Community Member

Modem troubles

we're using a 2801 router with mgcp for bri interfaces and fxs interfaces.

When an analoge phone is connected at the fxs port, it's working fine. A fax or modem is not working correctly. sometimes it's okay, but most of the time is lost the connection. Here's part of the config :

voice-port 0/3/3

no echo-cancel enable

no vad

compand-type a-law

cptone NL

timeouts interdigit 8

description H323 Test

mgcp modem passthrough voip mode nse

mgcp modem passthrough voip codec g711alaw

no mgcp fax t38 ecm

mgcp fax t38 inhibit

Community Member

Re: Modem troubles

your configuratrion needs to be looked into very well.are you using the right codecs.

also you can switch to a digital phones that has more feautures,appplications and lastly locate a more powerful modem than the one you are presently using


Re: Modem troubles

Try adding this to your dial peer:

fax-relay ecm disable

fax rate 7200

Some faxes fail with error correction.

Cisco Employee

Re: Modem troubles

I would check the outbound gateway. Many modem/fax issues I've seen are because of slips on the outbound trunks due to incorrect clock settings. A 'show interface' on the outbound trunks should tell you.


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