SIP Phones NAT issue on ASA 5505

[Mady]

Hi Team,

Please help me on this. The SIP phone is successfully registered to CUCM but the IP registered on it is its inside IP not the NAT'd IP.

But when we use SCCP phones the registered IP is its NAT'd IP.

CUCM - ASA- ISP - ASA - SIP IP Phones

Thanks for your help.

[Aditya Ganjoo]

Hi Mady,

Is it possible to share the show run of the ASA ?

Regards,

Aditya

[Mady]

Hi Aditya, I am afraid I cannot provide all the config. The registration of SCCP with successful NAT happened when SIP inspection is disabled. All ip phones are in Static NAT.

[Aditya Ganjoo]

Hi Mady,

If you examine the "VIA header" of the SIP invite and the IP addresses should  have been masqueraded (as per the NAT static rules).When the response sip packet is seen on the inside server, the "VIA header" ammended by the ASA should retain the INSIDE ip address.

Since the voice server is on the inside interface of the ASA you should see the inside IP and not the Nat'd IP.

Please check the following doc:

http://www.cisco.com/c/en/us/support/docs/security/asa-5500-x-series-next-generation-firewalls/82446-enable-voip-config.html#sip

Regards,

Aditya

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[Mady]

Hi Aditya,

Thank you very much for the inputs. I'll do study the docs you've provided.

Regards,

Madel