I have Apple TV 4K connected router A, IP is 192.168.1.10. Apple TV send Bluetooth Low Energy(BLE) advertisement with the IP. I captured by BLE sniffer.
I try "Screen Mirroring" from MacBook on router B, IP is 192.168.2.10 MacBook send "GET /info...RTSP/1.0" to appleTV:7000. Apple TV replay with 1368 bytes of "RTSP/1.0 200 OK..." that includes device name, type, features. But MacBook does not show my AppleTV as Display list. I like to know why my AppleTV is not recognized as mirroring display even all RTSP traffic has no error.
mDNS from AppleTV is blocked by router.
Ping from MacBook to Apple TV was success.
If Apple TV and MacBook connect on same router, screen mirroring was success.
Router A and B : Netgear Nighthawk Router netmask : 255.255.255.0 (both) MacBook : macOS Monterey 12.4 Apple TV : tvOS 15.6(19M65)