Apple TV crosses the vlan boundary

Hi,

I have a separate VLAN for my guest network and I cannot ping any of the devices on the private LAN from the Guest network.

However, I have an Apple TV on my private network which while cannot be pinged from the Guest network, iOS devices on the guest network can airplay to the device.

Have other folk experienced this? If so, do you know why this is the case?

Thanks
Shibby V138 on R7000