VIC-2FXO module and disconnection problems...

[ADB100]

I have a Cisco 1751V with a VIC-2BRI module and a VIC-2FXO module installed. The router is configured as an MGCP gateway and is working fine. I have one of the FXO interfaces connected directly to a UK PSTN line and I am having disconnection detection problems. i.e. If I call into the PSTN line and then hang up before the call is answered (I have an attendant DN configured in CCM) the FXO interface doesn't detect the disconnection and continues to ring.
I have been through the troublshooting guide on CCO but can't resolve the problem:

http://www.cisco.com/en/US/partner/tech/tk652/tk653/technologies_tech_note09186a00803736c1.shtml

I have tried various all variants of the 'supervisory disconnect' command but the FXO interface still cannot detect a disconnection.

Has anyone had this before and found a workaround?

Thanks

Andy

 

[MG2005]

what IOS?

 

[MG2005]

see if this helps, had this from a past issue. Forget what it was that fixed it tho, was a while back

http://www.cisco.com/en/US/customer/tech/tk652/tk653/technologies_tech_note09186a00800ae2d1.shtml

 

[pndscm]

Is making the PSTN line Ground Start an option?? That solves many supervisory problems.

 

[ADB100]

I have tried making the port Ground Start but this has makes no difference (I though the SP (BT) would need to make changes for this as well?). I have change cable polarity as well and this makes no difference either.

MG2005 - I have already been through the stuff on that page, but thanks anyway.

IOS is 12.3(14)T5 - but this problem has been there since I upgraded it from an earlier 12.3T release.

Andy

 

[jneiberger]

If you set your side to ground start, the provider must re-provision the line as ground start, as well.

 

[pndscm]

Change both ends to Ground Start. GS gives disconnect supervision. This will also help prevent 'glare' when 2 calls, 1 in, 1 out, hit head to head and connect together.

 

[jneiberger]

MG2005, that is an awesome link. I understood loop start and ground start signaling but I wasn't aware of the three types of supervisory disconnect methods for loop start trunks.

Thanks!

 

[ADB100]

I have no control over the service providers end, I can only change settings on the VIC-2FXO module. Is it possible I have the incorrect FXO module?

Andy

 

[jneiberger]

Your FXO module is working as intended. You are experiencing the joys of loop start trunks. Did you read the link that MG2005 provided? It explains the problem as well as the options you have for resolving it.

 

[ADB100]

I have been through all combinations of the 'supervisory disconnect' command and the problem remains. If I change it to 'anytone' then it is slightly better in that as soon as I answer the call the gateway disconnects if the caller had already hung up. Setting either 'signal' or 'dual-tone' as the supervisor disconnect option the gateway doesn't hang up until the receiver hangs up.

Are there any other settings I can try?

Andy

 

[jneiberger]

Even if you change those settings on your side, it remains to be seen if your provider is participating on those supervisory signalling methods. If they're not participating then changing settings on your side won't do any good. You might want to try calling them to see what they support. This may be a feature they can turn on for you. If not, changing the circuit to ground start is really the only good solution.