Iptables breaks a working VoIP phone?
kenneth at mail1.ttak.org
Sun Oct 28 22:57:14 MDT 2007
Gabriel Gunderson wrote:
> In general, I agree with this. But whatever you use, make sure iptables
> has a debugging mode where everything is logged before dropped. It's
> likely you will be able to look at your logs, see what is being dropped,
> and make changes to fix it.
> Good luck.
I have dropped packets being logged, and I can see the
source/destination IP and port of an occasional packet being lost. I am
not sure the packets I am seeing a from the direct phone call or some
sort of "ping" VoIP traffic. When I put in the rules where it would
forward ALL TCP/UDP traffic to the Sipra box, these logs would no longer
appear, but the phone calls were still broken.
The weekend is over and my wife wishes to have a working phone, so I
switched back to the Linksys router, and the phone began to work like
I am still determined to get the Linux firewall working, as I can do so
much more with the Linux firewall.
The only two thoughts I have as to what could be the problem are:
1. The Linksys does some sort of "special" NAT. The shorewall
configuration has both options for "NAT" and "masquerading", and I am
using the "masquerading" option. I assume this is just a 1 to many NAT,
where the "NAT" option is a 1 to 1 translation of NAT. I assume since I
only have one IP address, that the Linksys would be doing the
"masquerading" NAT that I have shorewall configured for.
2. Connection tracking. I know with FTP you had to have a special
connection tracking module, which is why I brought up that I had the
sip-tracking module loaded. I am wondering if it is not working right,
but I am not sure there are any configuration options, or even if I have
iptables/shorewall setup correctly to indicate this is SIP traffic.
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