[Serusers] Port mapping with Linksys wrt54g

Ladislav Andel ladia6 at centrum.cz
Wed Mar 29 14:58:09 CEST 2006


Hi Paul,
I've been using wrt54g too and have no problem with it.
STUN server tell me that my wrt54g is port restricted NAT and not 
symmetric NAT.
My WRT54G is version 2.
What firmware have you been using in your router? I have OpenWRT.

Yes I think TCP connection would help to it but you would have to keep 
open persistent connection by
keep-alives.

Lada

PREVOT Paul wrote:
>
> Hello,
>
> I am using a Linksys wrt54g router that applies Symetric NAT.
>
> When I register with my OpenSer proxy, I set my private IP address to 
> Via, Call-ID and Contact fields, because I have enabled 
> fix_nated_contact(); from the nathelper module.
>
> There is no problem with the registration. I get the OK back and 
> openserctl ul show returns public IP and public port in Contact field.
>
> Also, OpenSer knows an IP:port to use to forward me SIP messages, or 
> small UDP packets to keep the mapping on my NAT alive.
>
> To do so, I use modparam("nathelper", "natping_interval", 10).
>
> But I noticed that after each SIP transaction the router changes the 
> mapping used.
>
> It means Register and OK on port for example 10000 on the router’s 
> public interface and the next INVITE-OK-ACK through port 10005, a 
> second INVITE, through other port.
>
> So the mapping done for my 5060 port change very often and also as 
> soon as the register transaction is finished, it becomes false and 
> openSer can’t send me any Sip Message.
>
> There is no problem with MSN or Skype because the signalling is done 
> on TCP.
>
> Do you think registration using TCP instead of UDP will fixe the issue?
>
> Have you ever come across that issue? Can it be solved out differently?
>
> Thanks,
>
> Paul
>
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