[Firehol-support] VOIP with SIP/RTP and firehol stateful firewall

Andreas Unterkircher unki at netshadow.at
Tue Feb 19 04:51:02 GMT 2008

> I have been told from a person i know, that voip with sip/rtp wont work
> properly with a stateful firewall on the router.

It's a bit like FTP. You have one signaling channel (SIP) and then the 
channel for your voice (RTP). As the RTP stream got established between 
randomly selected ports, iptables may have problems with it, if you have 
a very strict ruleset.

But there for now ip_conntrack_sip exist (already in the mainstream 
kernel). Afterwards you only need to allow SIP in your firewall.


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