H.323 clients connected via GK-controlled Trunks?

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Jan 7th, 2008
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Hi everyone,

I'm trying to configure CM connected to a GK with H.323 clients registered with the GK.

It should be fairly simple but I've only got communication in one direction:

Calls from CM to the GK work perfectly. But calls from the GK-clients to CM do not work.

CM sees the call setup come in but, as it doesn't recognise the IP address, it just drops the call. We can MAKE it work by hardcoding the IP address as an H.323 phone but as they typically use DHCP this isn't a solution.

- Can anyone suggest the workaround - at the moment the CSS of the trunk is simply ignored?

- Is there anyway to force the setup message to come into CM from the GK instead of the originating device?

The SRND says DHCP clients are supported by configuring a route pattern to point to the H.225 trunk - but it doesn't say how to make it work in the opposite direction!

Many Thanks to everyone,


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Avner Izhar Tue, 01/08/2008 - 22:26
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What version of call manager are you using?

There is a call manager service parameter which disables that behavior of call manager, under 4.1 it is called "Accept Unknown TCP Connection" .

The other option is to use some sort of via zone gatekeeper integrated with ip2ip.

HTH, Avner.

stu_syn Wed, 01/09/2008 - 07:41
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Hi Avner,

Thank you - we're using 5.1 but that still has the "Accept Unknown TCP Connection".

I've tried changing this but it makes no difference. The SRND says:

"As discussed in previous sections, when a gatekeeper routes a call to the H.225 trunk of

Cisco CallManager, Cisco CallManager looks at the source IP address of the calling endpoint and tries to match that address to a device in its database. If it finds a matching IP address, Cisco CallManager applies that device's calling search space and other relevant settings. If it does not find a match, Cisco CallManager applies the calling search space and other relevant settings of the trunk."

I'm just not sure how it associates the incoming call with the trunk - any ideas?



Avner Izhar Wed, 01/09/2008 - 15:07
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Do you get the call rejected behavior from the first post, or do you see css problem now?

The service param is only for accepting calls from unknown ip addresses.

What do you see in the logs that tells you it is a css issue?

HTH, Avner.


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