I have an FXO port for a 1MB line on an H.323 gateway which forwards calls to a CUCM 6.0 server.
FXO Config:
voice-port 0/2/0
echo-cancel coverage 64
timing hookflash-out 50
connection plar 4488
description LINE FIVE
caller-id enable
Dial-peer config:
dial-peer voice 1000 voip
description TO-CUCM
destination-pattern ....
session target ipv4:10.2.0.1
dtmf-relay h245-alphanumeric
no vad
FXS Config:
voice-port 0/3/0
echo-cancel coverage 64
FXS Dial-peer config:
dial-peer voice 999230 pots
service mgcpapp
port 0/3/0
A fax machine is plugged into the FXS port. When the 1MB line is called, it will ring about 4 times and then you get about half a second of the fax beep and then then there is no more audio, though the call is not dropped and the faxes do not go through.
The FXS is registered correctly on the CUCM server. Other inbound calls work via 1MB lines on this router but this is the only one going to an FXS port.
