Before trying this verify your hardware configuration including correct port labels and order.
This guide is for Netgear n600 routers (WNDR3700 and WNDR37AV)
The port layout is as follows
Lan 1 = 0
Lan 2 = 1
Lan 3 = 2
Lan 4 = 3
CPU = 5
Go here to find yours: http://wiki.openwrt.org/toh/start
*******Configure your Network settings (/etc/config/network) following these steps:******
### Step 1 add your interfaces ###
config interface vlan2
option ifname eth0.2
option type bridge
option proto static
option ipaddr 192.168.2.1
option netmask 255.255.255.0
config interface vlan3
option ifname eth0.3
option type bridge
option proto static
option ipaddr 192.168.3.1
option netmask 255.255.255.0
config interface vlan4
option ifname eth0.4
option type bridge
option proto static
option ipaddr 192.168.4.1
option netmask 255.255.255.0
### Step 2 add your default vlan0 config always using the cpu port ####
config switch_vlan
option device rtl8366s
option vlan 0
option ports "*5"
### Step 3 define and configure your vlans in this configuration ###
### I'm using all 4 ports one per vlan ###
config switch_vlan
option device rtl8366s
option vlan 1
option ports "0 5t" ### Notice the CPU port has to be tagged on all vlans ###
config switch_vlan
option device rtl8366s
option vlan 2
option ports "1 5t"
config switch_vlan
option device rtl8366s
option vlan 3
option ports "2 5t"
config switch_vlan
option device rtl8366s
option vlan 4
option ports "3 5t"
****Leave the remaining settings as is (unless you need specific configuration for WAN, etc)****
****Then Configure your DHCP servers (/etc/config/dhcp) for each new Vlan****
config dhcp lan
option interface lan
option start 100
option limit 150
option leasetime 12h
config dhcp vlan2
option interface vlan2
option start 100
option limit 150
option leasetime 12h
config dhcp vlan3
option interface vlan3
option start 100
option limit 150
option leasetime 12h
config dhcp vlan4
option interface vlan4
option start 100
option limit 150
option leasetime 12h
****Leave the remaining settings as is (unless you need specific configuration for WAN)*****
*****Finally configure your firewall (/etc/config/firewall) to allow Internet access for your newly created Vlans*****
config zone
option name lan
option network "lan vlan2 vlan3 vlan4"
option input ACCEPT
option output ACCEPT
option forward REJECT
*****And you are done*****
Enjoy!