/etc/config/network:
config interface 'wan3'
  option proto 'dhcp'
  option ifname 'eth3'
  option delegate '0'
  option defaultroute '0'
  option peerdns '0'

config interface 'wan4'
  option proto 'dhcp'
  option ifname 'eth4'
  option delegate '0'
  option defaultroute '0'
  option peerdns '0'

vytvořit v /etc/iproute2/rt_tables
10 wan3
11 wan4

a po restartu:

ip link add eth3 link eth2 type macvlan
ip link add eth4 link eth2 type macvlan
ip rule add from $(ip a | grep 'scope global eth3' | awk '{print $2}' | cut -f1  -d'/') table wan3
ip rule add from $(ip a | grep 'scope global eth4' | awk '{print $2}' | cut -f1  -d'/') table wan4
ip route add default via $(ip r | grep 'eth3  proto static' | awk '{print $1}') table wan3
ip route add default via $(ip r | grep 'eth4  proto static' | awk '{print $1}') table wan4