echo "1 isp1" >> /etc/iproute2/rt_tables
echo "2 isp2" >> /etc/iproute2/rt_tables

# IPv4 routes
ip rule add from 172.16.20.0/24 dev eth0 table isp1
ip rule add to 172.16.20.0/24 dev eth0 table isp1

ip rule add from 172.16.30.0/24 dev eth1 table isp2
ip rule add to 172.16.30.0/24 dev eth1 table isp2

ip route add 172.16.20.0/24 dev eth0 src 172.16.20.10 table isp1
ip route add default via 172.16.20.1 dev eth0 table isp1

ip route add 172.16.30.0/24 dev eth1 src 172.16.30.10 table isp2
ip route add default via 172.16.30.1 dev eth1 table isp2

# IPv6 routes
ip -6 rule add from 2001:db8:20:1::/64 dev eth0 table isp1
ip -6 rule add to 2001:db8:20:1::/64 dev eth0 table isp1

ip -6 rule add from 2001:db8:30:1::/64 dev eth1 table isp2
ip -6 rule add to 2001:db8:30:1::/64 dev eth1 table isp2

ip -6 route add 2001:db8:20:1::/64 dev eth0 src 2001:db8:20:1::10 table isp1
ip -6 route add default via 2001:db8:20:1::1 dev eth0 table isp1

ip -6 route add 2001:db8:30:1::/64 dev eth1 src 2001:db8:30:1::10 table isp2
ip -6 route add default via 2001:db8:30:1::1 dev eth1 table isp2