Для создания отдельных интерфесов на кождом из портов ASUS WL-500W, нужно разделить порты vlan'ами:
root@OpenWrt:/# cat /etc/config/network
#### VLAN configuration
config switch eth0
option enable 1
config switch_vlan eth0_0
option device "eth0"
option vlan 0
option ports "0 5"
config switch_vlan eth0_1
option device "eth0"
option vlan 1
option ports "1 5"
config switch_vlan eth0_2
option device "eth0"
option vlan 2
option ports "2 5"
config switch_vlan eth0_3
option device "eth0"
option vlan 3
option ports "3 5"
#config switch_vlan eth0_4
# option device "eth0"
# option vlan 4
# option ports "4 5"
#### Loopback configuration
config interface loopback
option ifname "lo"
option proto static
option ipaddr 127.0.0.1
option netmask 255.0.0.0
#### PORT 1
config interface lan1
option ifname "eth0.0"
option proto static
option ipaddr 192.168.10.1
option netmask 255.255.255.0
#### PORT 2
config interface lan2
option ifname "eth0.1"
option proto static
option ipaddr 192.168.20.1
option netmask 255.255.255.0
#### PORT 3 configuration
config interface lan3
option ifname "eth0.2"
option proto static
option ipaddr 192.168.30.1
option netmask 255.255.255.0
#### PORT 4 configuration
config interface lan4
option ifname "eth0.3"
option proto static
option ipaddr 192.168.40.1
option netmask 255.255.255.0
#### WAN configuration
config interface wan
option ifname "eth1"
option proto static
option ipaddr 192.168.195.66
option netmask 255.255.255.0
option gateway 192.168.195.65