[ramsamba]

Wifi Router: DLink DIR-600 rev B1
Firmware: DD-WRT v24-sp2 (03/25/13) std

This entry is to share my knowledge after having found out my problem with the following setup:

1. Repeater Bridge connecting to my host modem-wireless-router, which i will refer to as host router.
2. Virtual Interface (VAP) that has a different SSID than the host router

The reason my repeater-bridge router and host router have different SSIDs is because my devices tend to have their connections dropping or take a long time to connect, or not connect at all to the wifi.

The solution to that was to have a different SSID (from the host router SSID) set up on a virtual interface on the repeater-bridge wifi router.

In my DLink DIR-600 modem, every time I created a virtual interface, my connection to the host router would drop.

The solution was to clone the MAC address of the wireless interface, which is the solution I got from here, as revealed by "Boyscout" in the comments:
https://jgiam.com/2012/07/06/setting-up-a-repeater-bridge-with-dd-wrt-and-d-link-dir-600

Before I created the virtual interface, I went into the menu: Setup > MAC Address Clone,
- MAC Clone: set to Enabled
- copied the Clone WAN Mac into the Clone Wireless MAC,
- then Save, Apply Settings
- Back to Wireless > Basic Settings, and refresh the page, and the cloned MAC will now show in the "Physical Interface...HWAddr[<cloned MAC address>]
- Next, create the virtual interface by clicking on Add in the Virtual Interface section of the same page
- Save, Apply Settings
- Go to menu Wireless>Wireless Security, and duplicate the settings of the Physical Interface into the Virtual Interface.
- Save, Apply Settings

Done!!

Hope this helps someone. I spent 10 hours trying to make this work.