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Desk Phone Pickup problem with Mobile Connect (UCM8.5)


I have issue with desk phoen pickup when having mobile connect setup. The environment is using UCM 8.5SU2. The remote destination phone is ok and the mobility transfer to remote phone is also working fine. The symptoms and steps are:

1. User A call IP  phone B

2. Phone B and remote phone rang together - this is FINE

3. When we answered the cal from remote phone, it was connected well.

4. remote phone hang up then user A heard engaged tone straight. However IP Phone B will provide the resume button after 37 seconds and was able to pick up the call as long as user A has not hang up.

I looked at the Cisco Voice GW config, all seems good except there is a CLI "isdn alert-end-to-end". I never used this command and suspect might be the cause. Has anyone experience the same problem? Thanks


Steve Burdick

I am experiencing the same problem, but with a different setup.

1. Running CUCM7.1.5 instead of UCM8.5

2. Voice gateway is a 2611XM running IOS Version 12.4(25d).

Have you found any workaround?

not yet. I am going to raise TAC case on this issue.

Hi Steve,

My problem is fixed now. It is telco issue which sent the disconnect signal after 35 seconds. You can turn on ISDN q931 debug on the IOS GW and check for this. Hopefully this will fix yours too.

Hi Robin,

What was it that fixed the problem? Configuration change on your side or the telco's?

Hi Steve,

Once you confirmed the disconnect signal is sent by telco after long period of time (35s in my case), then you need to contact the PSTN provider to fix this. There's nothing to do from customer's end since the root cause is at Telco side. You may send the ISDN Q931 debug output to telco engineer to prove that IOS GW is functioning properly.

FYI My problem was resolved by switching IOS versions. I blame IOS version 12.4(25d).

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