[Asterisk-Dev] Feature request: auto-guessing NAT status based on From: IP address

[Mark Spencer]

What sort of device do you have that does not work with nat=1 when nat is
not actually taking place?

As far as I know, the pingtel is the only one.

Mark

On Wed, 16 Apr 2003, John Todd wrote:

>
> [Sorry to put this up to the list instead of submitting code; I can't
> code my way out of a wet paper bag, as I've said before.]
>
>
> Proposal:
>
> Extension to the "nat=" flag in sip.conf to automatically guess on NAT status.
>
> Reason:
>
> I have a bunch of people that keep moving their SIP devices between
> home and work (NAT and non-NAT IP space) and I get tired of switching
> their "nat=" status every time they move.  Most (but of course, not
> all) NAT devices give out RFC1918 addresses, so in any given REGISTER
> or INVITE status we have a pretty good idea if a device is NAT'ed or
> not.  Why not use that data to solve the problem for the 90% of the
> people who have NATs that provide addresses in this space?  Retaining
> the "yes" and "no" flags maintains backwards static compatibility for
> those who need it or for address spaces that are NAT'ed but do not
> fall into the RFC1918 area.
>
>
> Syntax:
>
> Old syntax:
>   nat=[1,0]
>
> New Syntax
>   nat=[1,0,yes,no,auto]
>
> The "0" and "1" definitions will retain their historical meaning, and
> will also have duplicates with the terms "yes" and "no" to mean "1"
> and "0" respectively.
>
> If the keyword "auto" is specified, the system will make a 'best
> guess' as to the status of the NAT flag for that SIP peer.  If the IP
> address in the "From:" field in an INVITE or REGISTER is set to one
> of the common RFC1918 addresses, then the system will assume "yes"
> and the appropriate re-write and "via" headers will be set.
>
>
> Definitions:
>
> RFC1918 space:
>
> 10/8
>    - match on first octet being a "10"
>
> 172.16/12
>   -  match on first octet being 172, and second octet being between 16 and 31
>
> 192.168/16
>   - match on first octet being 192, and second octet being 168
>
> See RFC1918 (http://www.zvon.org/tmRFC/RFC1918/Output/index.html)
>
>
> JT
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