NAT traversal for H.323 gateway

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Jul 24th, 2009
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I need help with following scenario: I have CUCM cluster in my private subnet with addressing. Also I have 2821 gateway with 2 interfaces: one in subnet and second interface resides in another subnet with real IPs. I need to create connection between CUCM and a H.323 GW in the outside network. How do I need to configure NAT on 2821 GW to allow inbound connections to pass to CUCM from the outside GW?

Thank in advance!

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dfokin Mon, 07/27/2009 - 22:38
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Thank you for your reply. I have tried to establish static NAT, but unfortunately, this works in wrong way. I have no problems with signaling, but have problems with RTP, because RTP traffic goes between IP phones and external GW and I need to somehow establish dynamic NAT rules to forward RTP traffic to IP phones, instead CUCM.

chiawong Tue, 07/28/2009 - 00:14
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I'm not sure how your topology looks like, but i have a lab setup below that works, allowing the CUCM IP phones to call the CME phones and vice versa.

CUCM+IP phones -- NAT router --- h323 GW --- CME router --- CME phones

The CUCM+IP phones are in the "inside" network, and NAT router does static NAT for the CUCM and PAT for the IP phones. CUCM is configured with a route-pattern pointing to the h323 GW for the CME phone numbers. while CME has a dial-peer pointing to the H323 GW for the CUCM IP phone numbers. The h323 GW is effectively an IPIPGW and is configured with the appropriate dial-peers.

You may want to try to configure PAT for the IP phones, static NAT for the CUCM in the inside network to see if that works.

dfokin Tue, 07/28/2009 - 02:17
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Topology is the same. I will try to do PAT, as you have suggested. Thanks.


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