[SIPForum-discussion] Change of contact field when behind NAT

Mohit Soni Mohit.Soni at matrixcomsec.com
Tue Oct 8 05:31:48 UTC 2013

Hi Rahul,



In the behind the NAT scenarios, the SIP UAC should change the IP Address in
the Contact, VIA, "c=" and "m=" for successful calls.


However, if the SIP UAS is Outbound Proxy or B2BUA then they have symmetric
signaling and Symmetric RTP implemented to overcome the NAT issues.

So, in that case, the calls will be successful even if the UAC is not
changing the IP Address  and Port in Contact, VIA, "c=" and "m=" fields.



Best regards,

Mohit Soni


From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of rahul sankanur
Sent: Tuesday, October 01, 2013 4:30 PM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] Change of contact field when behind NAT


Hello all,


When we are behind NAT, we need to change the 'c=' field and the 'm=' field
for changing the ip address and port respectively.


I wanted to know if we have to change the contact field in the message
header when we are behind NAT..Does the rfc specify the change ?


Best regards,

Rahul Sankanur

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