by custom firmware, do you mean 3rd party? If so, you'll have to check the websites for that firmware for the details on it, I don't use 3rd party firmware, as if there's a problem, it could be really bad, and it's also possible for someone to program the firmware to send a copy of all Internet data to a specific IP, so I wouldn't trust my data's defiantly safe. Stick to official firmware, unless your wanting to do something very special/specific, it'll be able to do it just as well/better than any 3rd party firmware.