NAT with RTP

[Henrik Nordstrom]

Only provided both route their traffic via the netfilter NAT router.

The problem is return traffic. If both are in the same network then 
they will normally send return traffic directly to the other, 
bypassing the NAT router, and this obviously won't work that well in 
most cases.

What can be done is to fool the other that the caller is on an 
address that will be routed via the NAT router. This can be done by 
NAT the source IP address as well as the destination on such 
connections.

Regards
Henrik



On Wednesday 17 April 2002 05:20, luoqiang wrote:
> Hi,
>
> I am a newbie for netfilter and is planing a SIP enabled module
> with netfilter, but some question puzzled me.
>
> 10.10.1.2¡ª¡ª159.226.1.1¡ª¡ª159.226.1.2¡ª¡ª10.10.2.2
> A------>B£¨GW:10.10.1.1)-->C(GW:10.10.2.1)-------->D
> A(159.226.1.1:10000)
> D(159.226.1.2:10000)
>
> There are two NATs,  host A and D are in the NAT.
> If A have known the IP address and port of D which had been
> mapped(159.226.1.2:10000), can A send RTP packet to D directly?
> In other word,if A and D had known the others mapped address,
> can A communicate with D directly?
> Does  ip_nat_expect_register() founction  in netfilter can fulfil
> above goal?
>
> Thanks