[asterisk-users] SIP reply CALL-ID from ITSP has internal address in host part

[Alex Balashov]

Andrew Stewart wrote:

> We are using using what Cisco's Port Address Translation, so that all
> SIP traffic is done through %EXTERNIP%.  To any outside box, it should
> look like the asterisk server is actually on %EXTERNIP%.
> 
> My SIP packet gets sent to the ITSP with a Call-ID:
> 2fd557964ca936b66661d72f1328c918@%EXTERNIP% , but the SIP 200 OK reply
> from ITSP has Call-ID: 2fd557964ca936b66661d72f1328c918@%INTERNIP%.  I
> can not figure out where the ITSP is even getting my %INTERNIP% from,
> I don't see it in the packet anywhere.

This doesn't seem quite right.  If the 200 OK reply is truly for the 
INVITE (or whatever other transaction is initiated by your "SIP 
packet"), it *must* have the *same* Call-ID per the RFC, otherwise it's 
not a valid reply.

The Call-ID is what's called a GUID (Globally Unique IDentifier).  It is 
up to every SIP user agent to generate one, and the only requirement is 
that it be as unique as practical in time and SIP space.  Many network 
elements like to tack on IP addresses in the GUID as a means of 
differentiating it further, though personally I think that's a bad idea.

Would you mind pasting a capture of the transaction in question, from 
the vantage point of the outside interface of your Asterisk host?  You 
can change the representations of the external IP to something else if 
you don't want to post it to a public list.

Thanks,

-- 
Alex Balashov - Principal
Evariste Systems
Web     : http://www.evaristesys.com/
Tel     : (+1) (678) 954-0670
Direct  : (+1) (678) 954-0671