Routing

The Linux `route` command

Below is a list of useful commands

# show the routing table, with numeric addresses
route -n
# add a default route, through eth0
route add default dev eth0
# add a route to 10.150.0.0/24 through eth0
route add -net 10.150.0.0/24 dev eth0
# add a route to 10.150.0.0/24 through eth0, and the gateway 192.168.0.15
route add -net 10.150.0.0/24 gw 192.168.0.15 dev eth0

SIOCADDRT: No such process

The most unhelpful error possible. It generally means you have done something silly... check:

• Your addresses - e.g. is the gateway you specified actually directly accessible through the interface?

Setup NAT

To setup NAT between interfaces eth0 (outside) and tun0 (inside - e.g. a VPN server)

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A FORWARD -i eth0 -o tun0 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i tun0 -o eth0 -j ACCEPT