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network_user
Beginner

Help!! Cisco 8811 (SIP) behind NAT registering to CUCM

Hello,

I have a Cisco IP phone 8811 (SIP) which is behind a Cisco 2821 router. This phone NAT's to public IP on Cisco 2821 and then registers to a CUCM on internet. When it registers,  CUCM has phone's private IP address instead of Public. I think the problem is that Cisco 2821 is not able to do SIP ALG for Register request that phone send to the CUCM. I see phone sends a SIP register message which is TCP and sent to TCP port 5060 to CUCM. When I try configuring SIP ALG on Cisco 2821, it gives me an option to configure the SIP NAT service only for UDP port.

Is there any other way I can make Cisco 2821 to do SIP ALG on TCP 5060? If not, is there a way I can configure the phone to send the SIP register message on UDP 5060 instead of TCP?

From Cisco 2821 (does not give me a TCP option):

(config)#ip nat service sip ?
udp UDP protocol

Thanks!

3 REPLIES 3
network_user
Beginner

Does anyone has any clue on how I can fix this without a VPN?

network_user
Beginner

Any ideas???

Pasha Teplitsky
Beginner

Hi,

8800 phones do not support SIP over UDP.

SIP ALG for TCP is supported depending on your IOS version.

This is probably what you are looking for.

Let me know if it helps.

Pasha

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