TPLink with stock firmware doesn't have VLAN tagging. (621 for Maxis)
So, you need to flash TPLink 1043 into custom firmware to get VLAN tagging.
I am using OpenWRT now and it works.

Check your hardware revision of TPLink. (Refer to sticker on your box)
Read the table from below link carefully for correct firmware to download.

http://wiki.openwrt.org/toh/tp-link/tl-wr1043nd

If you are on revision V1.10, you can download the firmware from this link :

http://downloads.openwrt.org/attitude_adju...hfs-factory.bin

The rest just follow instruction from klseet

http://www.klseet.com/index.php/tl-wr1043nd-ver18

Step is the same, klseet is using unifi and we are using maxis with different vlan.

You need to follow this for VOIP to work

http://forum.lowyat.net/topic/2710206