phaoost's diginotes

Quick setup IP-over-IP (protocol 4) tunnel on Debian 5.0

192.168.x.x - router LAN IP
192.168.x.y - local LAN IP
172.16.x.x - router tunnel IP
172.16.x.y - local tunnel IP

On router add to /etc/network/interfaces:

# ipip tunnel
iface ipip0 inet static
address 172.16.x.x
netmask 255.255.255.255
pointopoint 172.16.x.y
mtu 1480
pre-up /sbin/ip tunnel add ipip0 mode ipip remote 192.168.x.y local 192.168.x.x dev eth0
post-down /sbin/ip tunnel del ipip0

On local system add same lines to /etc/network/interfaces switching local and remote IPs. Then use ifup/ifdown to add/remove ipip0 interface

Following rule may need to exist in iptables mangle table on both systems:

-A FORWARD -p tcp -m tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu