[Asterisk-Users] SIP Nat Issue

[Olle E. Johansson]

Eric Wieling wrote:

> On Mon, 2003-10-20 at 11:31, Chris Albertson wrote:
> 
>>Asterisk works perfectly fine in back of a NAT firewall, as long
>>as all of your SIP phones are also in back of that same fire
>>wall ;-)
>>
>>Seriously, I'd fix this if I knew enough about SIP protocol.
>>Is anyone willing to write up what is required at the "bit and byte
>>level"?   One thing that could help is try this and report
>>findings:
>>
>>X-Lite _can_ dail out to FWD through a firewall but Asterisk can't.
>>SO this gives us the perfect chance to compare the content of
>>outbound packets where we have a working and non-working example.
>>
>>I'd look into hacking Asterisk to mimic the X-Lite generated
>>SIP protocol.  
>>
>>Put the result on the wiki.  Doing this will greatly speed up
>>the fix.
>>
>>
>>
>>--- WipeOut <wipe_out at onetel.com> wrote:
>>
>>>Mark Evans wrote:
>>>
>>>
>>>>Hi All
>>>>
>>>>Has anything been done to fix the issue where the * box is sat
>>>
>>>behind a
>>>
>>>>nat firewall?
>>>>
>>>>Regards
>>>>
>>>>Mark
>>>>
>>>> 
>>>>
>>>
>>>As far as I know it can't be done.. The server has to be on a public
>>>IP..
>>>
>>>You could try using a SIP aware router like the intertex range but I 
>>>don't know how much milage you will get from that..
>>>
>>>Later..
>>>
 > Actually it requires CHANGING the SIP protocol.  Asterisk already
 > changes the SIP protocol when you use nat=yes and many clients also
 > change the SIP protocol to work with NAT.
 >

Well, it requires changing messages exchanged in the SIP protocol.
The outbound proxy may want to change data in the SDP body when
doing an invite, so the media path for the incoming media stream
has to be changed.

/O