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Joined: Jun 2008
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Hi all. Having this issue intermittantly for a few months now. Here's the layout in a nutshell.
Running CM 4.1(3) in location A
IPSec tunnels (3.0Mb NxT1) between 4 locations(A, B, C, D) dedicated to VoIP traffic
Cisco 2811 voice routers in each locations configed for H323
All phones are either Cisco 7940 or 7960 DHCP addys

Issue is that even though IPSec tunnels are up (can ping and telnet between devices), phones will register normally and calls will connect to each other, but callers cant hear each other...just dead air. After a while...maybe a few hours things go back to normal.
VPN endpoints are Cisco VPN-3005 concentrators using DES-56 encryption authentication is ESP/MD5/HMAC128

Stumped here.
I'm almost positive its a routing issue...but where? It works most of the time!
UDP issue perhaps?
Any help would be great.
Thanks

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Joined: Aug 2005
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Somehow your RTP steam is not routing. Sounds to me like either a H.323 or MGCP issue. Which protocol are you running? Are you binding the address of the voice gateway to a loopback interface? Can you ping that loopback interface? Do you have a static route in the 3k5 concentrator pointing to the loopback? Do have the loopback in your network list in both 3k5s? This is what I would check first.

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We're running H.323. Hmmm. If there's any truth to that...why would it be intermittently then instead of a persistent problem?

Joined: Aug 2005
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You are right in saying the it should be persistent and not intermittent. Do you have the h323-gateway voip bind srcaddr 10.1.1.1 command on the voice interface? It really sound like the issue is related to the RTP stream. Can you ping the h323-gateway voip bind srcaddr 10.1.1.1 when you are having the issue? There are no fixup protocols on the concentrator so I am not thinking the problem is related to that.

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One other thing I just thought off, are you transcoding your calls on the other side of the concentrator. Have you checked your media resource lists? What device pool are they in? Possibly you are out of media resources? Try setting all of the phones on the other side to G.729, but make sure you have the media resources to do it. What codec are you running on the LAN?


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