[asterisk-users] SIP and Firewall

[Guenther Sohler]

Dear Group!

I want to improve the firewall rules for SIP
and I already compiled the linux kernel with additional SIP netfilter
settings

Now I found this on the internet:


modprobe ip_conntrack_sip ip_nat_sip

Set IPtables filter rules

iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -p udp --dport 5060 -j ACCEPT

Set IPtables NAT rules

iptables -A FORWARD -o eth0 -p udp --dport 5060 -j ACCEPT
iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source ip.add.dr.ess

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But I do not understand it. where is eth0 connected to in this example ?
and what would be the source ip adress ? what will happen if i amn connected to 2 sip gateways ?



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