Veja o padrão de gateway linux
ip route
# first line is your default gateway, next lines are your other routes
Clever Capybara
ip route
# first line is your default gateway, next lines are your other routes
sk@sk:~$ ip route show
default via 192.168.1.1 dev eth1 proto static
192.168.1.0/24 dev eth1 proto kernel scope link src 192.168.1.100 metric 1
ip route add default gw {IP-ADDRESS} {INTERFACE-NAME}