I setup a gre tunnel a cisco router and a Linux machine, the tunnel interface in the Linux box named pic.
Well i have to forward traffic coming from cisco through the Linux box.
the rules i’ve set in the Linux box is described as follow:
echo "1" > /proc/sys/net/ipv4/ip_forward
iptables -A INPUT -p 47 -j ACCEPT
iptables -A FORWARD -i ppp0 -j ACCEPT
iptables -A FORWARD -i pic -o ppp0 -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i ppp0 -o pic -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE
I see the traffic coming from tunnel and forwarded to internet but no reply from sent packet.
May i miss something like a routing rule.