As long as that Netgear is on the latest firmware, it should work. I've honestly never run into multicast protocol issues with Netgear routers in a long time. Try maybe updating the firmware on that, make sure UPnP (Universal PnP) is turned on on the router and all else fails, just restore to factory and reconfigure it. While you're at it, might as well make sure you're on WPA2/AES security for it. (You're doing all the legwork to reconfigure it anyway, might as well bump up the security the current standards while you're at it.) Also, make sure both your laptop and AppleTV have good signal and speed on the WIFI network. A weak signal could have issues with the mirror function since it's a bit more intensive than pure streaming is.
BTW, as long as your MacBook displays the AirPlay mirroring icon on the Finder menu bar, it is properly seeing that device as available for the necessary protocols. If that works, but the mirror portion doesn't, that points more to a possible network speed issue, but taking care of the above listed things will get you started with a nice clean stable base to work from.