Dropped calls on IOS h.323 gateway and CUCM 6

Unanswered Question
Feb 5th, 2010

Hello everyone,

I've got a very vexing issue.  I converted a router over from MGCP to h.323.  IOS Advanced IP Services 12.4-4(t).  With MGCP there was never an issue with dropped calls.  Ever since switching gateway over to h.323, any calls are dropped with alarming regularity within 5 minutes or less of call being established.  I am using the VIC-2FXO-M1 as my gateway interface.  I've been searching for information on this and have come up with nothing.  Unfortunately, MGCP will not allow CallerID over MGCP using FXO at this time.  I'm not sure what is causing this dropping of calls.  Any ideas?

On another note, is it possible to setup a SIP trunk between CUCM to the router and still use the 79xx phones as SCCP?  Not sure on that either.  If it is something with h.323, that would be an alternative solution but I think unnecessary.  The 79XX (type A) phones don't work as well using SIP unfortunately.  Thanks for any information.

I have this problem too.
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fieryhail Fri, 02/05/2010 - 10:28

I changed the router config to act as a sip-server.  Configured a SIP trunk in CUCM and pushed calls through that instead of h.323 gateway.  Seems to have solved the issue.  Still curious as to why that was happening.  Any ideas?

fieryhail Fri, 02/05/2010 - 10:35

I take back my previous post.  The problem is still not solved.  It seems that no matter what I do, I keep getting dropped calls.  Is it the VIC itself?  And how would I test for such?  Thanks.

ausjustin Wed, 09/03/2014 - 04:43

Hi Fieryhail 


Have you fixed your issue ? I had same problem like your one . 

1.       Intermittent call drop outs
2.       call hang up / call termination / end call delay issue around 30 second delay 


gogasca Fri, 02/05/2010 - 10:43

Any Firewall in the middle? between CUCM and IOS GW?

H323 establishes a TCP connection b/w CUCM and IOS GW

if for some reason this connection is dropped either H225 or H245 call is dropped as well

We have a Service parameter that helps to prevent this

Allow Peer to Preserve  H.323 Calls

But is only a workaround, investigation needs to be done if above theory is true.



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