Second Step - Setting up Network B and establishing the trunk on port 4

1)  Back to the telnet window. Copy the following script and paste on the command line.  

 ------------------- Copy starting below this line. ------------------- 

nvram set vlan2ports="1 2 3 4t 5t"

nvram set vlan3ports="4t 5t"

nvram commit

echo '

#!/bin/ash

PATH="/sbin:/usr/sbin:/bin:/usr/bin:${PATH}"

iptables -I FORWARD -i br0 -o vlan3 -j ACCEPT

iptables -I FORWARD -i vlan3 -o br0 -j ACCEPT

iptables -I FORWARD -i vlan3 -o vlan1 -j ACCEPT

iptables -I INPUT -i vlan3 -j ACCEPT 

ip addr add 192.168.2.1/24 brd + dev vlan3 

ifconfig vlan3 up

' > /jffs/etc/config/vlan3.startup 

chmod 750 /jffs/etc/config/vlan3.startup

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2)  On port 4 select the tagged checkbox and then select VLAN 3.

 i

3)  Click the Save Settings button at the bottom of the page.

4)  Back to the telnet window.  At the prompt type reboot and hit <enter>

Your WRT should be configured and port 4 is a 802.1q trunk with both VLAN 2 and 3 present and tagged. (Network A and B)