auto eth0
iface eth0 inet static
  address 198.51.100.87
  netmask 255.255.255.0
  gateway 198.51.100.1
  post-up ip route add 198.51.100.0/24 dev eth0 table 1
  post-up ip route add default via 198.51.100.1 table 1
  post-up ip rule add from 198.51.100.87/32 table 1 priority 100
  post-up ip route flush cache
  pre-down ip rule del from 198.51.100.87/32 table 1 priority 100
  pre-down ip route flush table 1
  pre-down ip route flush cache

auto eth1
iface eth1 inet static
  address 203.0.113.144
  netmask 255.255.255.0
  post-up ip route add 203.0.113.0/24 dev eth0 table 2
  post-up ip route add default via 203.0.113.1 table 2
  post-up ip rule add from 203.0.113.144/32 table 2 priority 110
  post-up ip route flush cache
  pre-down ip rule del from 203.0.113.144/32 table 2 priority 110
  pre-down ip route flush table 2
  pre-down ip route flush cache