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Community Member

QSIG PRI not coming up

I'm trying to configure a QSIG T1 PRI on a 3825 running 12.4(8) but the link is not establishing. I have the router configured to be the network side but it

appears to be ignoring that command. Here is the output from "debug isdn


*Jun 26 22:38:53.242: ISDN Se0/0/0:23 Q921: L2_EstablishDataLink: sending SABME

*Jun 26 22:38:53.242: ISDN Se0/0/0:23 Q921: Net TX -> SABMEp sapi=0 tei=0

*Jun 26 22:38:54.242: ISDN Se0/0/0:23 Q921: Net TX -> SABMEp sapi=0 tei=0

Isn't that backwards? According to the CiscoPress book Troubleshooting

Cisco IP Telephony, the SABME frames should be incoming from the user side if

the router is configured as the network side. Instead, the router still appears

to be sending the SABME, which makes me think that the link isn't coming

up because both sides are acting as the user side. Our PBX guru says that the errors she's seeing indicate that the PBX is receiving frames that it should not be receiving.

From that debug output, can you tell me if the router is actually behaving as

the user side even though I have "isdn protocol-emulation network"


I checked the Bug Toolkit and I don't see any bugs related to this.



Re: QSIG PRI not coming up

Since is MGCP the configuration will be downloaded from CCM including Network|User side.

Check that CCM config is ok.

And yes, to establish the D channel the user side must send a SABME message and the Network side respond with a UAf message

Community Member

Re: QSIG PRI not coming up

Both CCM and the router config states that the gateway should be acting as the network side. I think this may be a bug. I'm going to try switching things around tomorrow so that the router is the user side. I'll be okay as long as that works. If it doesn't work, I'm in trouble. :-(

Community Member

Re: QSIG PRI not coming up

I opened up a TAC case and discovered that the troubleshooting book is a little misleading. In reality, either side (or both sides, actually) can send the SABME frame, but only the network side responds to it. I dug a little deeper and noticed that we weren't receiving ANY frames from the PBX. I think we probably have a case of one-way communication. I'll replace the cables and connectors tomorrow and see what happens.

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