On my new box, port 30100 is open, though. No idea what it's for.
EDIT: Interesting. It does seem to create local LAN UDP traffic to port 33484 on the box. Large amounts while playing video. A 32 byte packet every second while idle.
EDIT2: The UDP traffic seems to be initiated by the box.
Also, I'm seeing UDP broadcast traffic from the cameras that are connected to the box's ethernet ports leaking into the LAN. I wonder if the box will route the traffic somehow. This after the box broadcasts 51a80000000000000000000000000000 from port 18153 to 18152. The camera message comes from port 18152 to port 18153.
EDIT3: If you add routing to 192.168.138.0/24 to the IP address of the CCTV box, it also responds at address 192.168.138.99. No difference in which ports are open, though. It does not seem to route the cameras.
EDIT4: Set your own IP address in the 138 range (below 99), the cameras appear to be reachable directly. The CCTV box acts like a regular switch between the LAN and PoE ports. Camera has open ports 23, 554, 8000, and 8080.
Port 554 on the camera:
RTSP/1.0 400 Bad Request
Cache-Control: no-cache
Server: Hisilicon Ipcam
Port 23 on the camera:
(none) login:
Password:
Login incorrect