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New Member

Modem relay/passthrough via FXO

Modem relay/passthrough is introduced for 2600/3600 routers with 12.2(11)T, is this supported for FXO connection to the PSTN?? as it doesn`t seem to work properly. The modem will answer but not "train up". The Cisco configuration only mentions T1 connectivity.

4 REPLIES
Cisco Employee

Re: Modem relay/passthrough via FXO

Please describe a bit what you are trying to do. Is the GW MGCP? H323?

Where are the two modems that are trying to train?

Here is the feature page:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t11/ftmodrly.htm#xtocid6

New Member

Re: Modem relay/passthrough via FXO

Crieman

We are trying to connect a PC/Laptop via FXS port-IP-FXO port to a ISP, using H323. Consequently not sure on the modems used however have tried laptop modem to US Robotics 56k modem and this also fails. Interestingly the call is o.k. across the IP network from FXS to FXS (modem to modem) but not FXS to FXO on the same router and out to PSTN. Have also tried passthrough and that fails as well.

New Member

Re: Modem relay/passthrough via FXO

Got the exact same problem here but using FXS interfaces. I tried to have a simple VoIP connection between a 1750 and a 1751V router through a LAN using SIP. I loaded 12.2(4)XM4 IOS in both routers, but still having the same problem.

I worked around the situation by using G.711 codec in dial-peer configuration, but doing this doesn't involve the use of "modem passthrough" feature. Still investigating on this and already have a case opened with Cisco.

New Member

Re: Modem relay/passthrough via FXO

got the same probleme but using E&m and fxs interface using H323 . I worked around the situation by using G711 codec in dial-peer

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