NAT for H.323 on Cisco 2800 router

Unanswered Question
Mar 20th, 2008

Hello,I have configure NAT for H323 packets so that when call goes out of router it should be a natted ip address for outside world but its not happening.

Could some one tell if this is possible.:

NAT Configured:-

ip nat inside source static 10.0.10.10 10.88.1.80

And i have applied it to the interfaces aswell.

But when i see the traceroute:-

Internet Protocol Src:-10.88.1.80 dest:- 10.203.5.30(which is wrong)

TCP1720 is opened and there is no firewall inbetween which is blocking this.

Anyhelp on this would be appriciated.

Thanks in advance.

I have this problem too.
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bwilmoth Fri, 03/28/2008 - 08:32

VoIP protocols use dynamic port numbers that are negotiated while establishing a call. The port numbers and addresses are exchanged during the negotiation phase in the IP packet payload. This presents a challenge when configured along with NAT because NAT normally looks only at the IP header to do the translation.

Cisco IOS? Software has been enhanced with the Application Layer Gateway (ALG) feature, which is intelligent enough to automatically scan the addresses and port numbers carried in the payload of these protocols. This feature allows VoIP to work across a NAT router by setting up translations for the negotiated parameters.

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080093f96.shtml

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