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New Member

MGCP Gateway -- Fax/Modem configuration?


I have the following configuration.

PRI->2851 Gateway-CAS T1->Nortel PBX->Modem

There are no T1 problems between the Cisco and Nortel devices (no slips, etc) but modem/fax connections are slow and unreliable. Voice works perfectly.

I have some modem passthru commands on the MGCP gateway to support ATA186s that I have in service for fax machines, (they work well) but I am wondering if I need any additional commands for the Nortel device?

Here is my MGCP config as it stands:


mgcp call-agent CALLMANAGER-1 2427 service-type mgcp version 0.1

mgcp dtmf-relay voip codec all mode out-of-band

mgcp rtp unreachable timeout 1000 action notify

mgcp modem passthrough voip mode nse

mgcp quarantine mode process loop

mgcp package-capability rtp-package

no mgcp package-capability res-package

mgcp package-capability sst-package

no mgcp package-capability fxr-package

mgcp package-capability pre-package

no mgcp timer receive-rtcp

mgcp sdp simple

mgcp fax t38 inhibit

mgcp rtp payload-type g726r16 static


mgcp profile default


  • IP Telephony

Re: MGCP Gateway -- Fax/Modem configuration?

The command needs to be added is already added in the confgiuration "mgcp modem passthrough voip mode nse",

so i think the configuratiion is correct.

New Member

Re: MGCP Gateway -- Fax/Modem configuration?

I have the same issues. Calls through my ATAs work fine, but modems on the Nortel are unreliable. Did you find a fix for this?



New Member

Re: MGCP Gateway -- Fax/Modem configuration?

Unfortunately not.

I'm curious if it has something to do with the version of the analog line card I am using in the Nortel, but that is just a guess.