AirPlay over ASUS RT-N56U

I bought an Apple TV 3 today, intending to airplay stuff from the family's other Apple products; an iPad 2 and an iPhone 5. Turns out the AirPlay icon does not appear on either of the two. So obviously, they are not communicating with the Apple TV. All devices are connected on the same wireless network, via our ASUS RT-N56U router (firmware version 3.0.0.4.260). I have read online tonight about disabling the IGMP snooping, but I'm not able to find out how to do that.

So basically what I'm asking is what I can do to get this to work?

I have had problems in the past connecting to my work over VPN and also downloading/streaming contents from my Seagate NAS (uploading is no problem). I have not tried again after having updated the router firmware today. I suspect that the NAS and the AirPlay issues are related, whilst the VPN issue is something different. I have not yet tried home sharing, but I guess that too would not work.

Well, I hope someone out there can help...