iproute2 for Linux

eth0:
192.168.0.1

eth1:
10.0.0.1

destination      next
192.168.0.0/24   192.168.0.88
10.0.0.0/8       10.0.0.88

# ip route add default via 192.50.109.88 table ispA
# ip route add default via 150.65.118.88 table ispB

# ip rule add from 192.168.0.0/24 lookup ispA
# ip rule add from 10.0.0.0/8 lookup ispB

# ip route add default via 192.168.0.88