Configure Wireless Bridge to Main Tomato Router

Question

I have installed a tomato router in my home network as the main router. It is a Linksys E900 with Tomato (Shibby mod) release/version 121.

Now on the other side of the house, I have setup a HP V-M200, which is an AP without DHCP capabilities, but according to the manual it can be set as a WDS bridge.

According to the manual, for this setup, I have to

1. Set the main router to a AP + WDS Bridge routing mode.
2. Fix a wireless mode and a channel.
3. WDS-Link the bridge MAC in the main router.
4. Set the bridge router to a AP + WDS Bridge routing mode.
5. Fix the wireless mode and channel to those of the main router.
6. WDS-Link the main router MAC in the bridge router.

Now both routers have different IPv4 addresses and live in the same IP subnet.

On the main router device list, I can see the bridge router is recognized; its MAC address, and signal readings. However, on the bridge router, the WDS link appears as not running.

How could I debug this?

Edit 1: I found I can make it work by disabling security on the main router and disabling WDS security on the bridge router. However, now DNS is not working. I can only ping nodes in the LAN when I am connected to the bridge (gateway included). It is not optimal for me to have network security off in the main router, but there seems to be no separate setting for WDS security.

Edit 2: DNS is working indeed, my mistake. However, ping packets seem unable to reach past the main router, so when one is connected to the bridge router, ping packets to outer nodes never return. What could be causing this?