Internet-Security.com UDP port 253 details

UDP port 253 is assigned to MADCAP (Multicast Address Dynamic Client Allocation Protocol).
Microsoft Windows Server’s DHCP service implements a MADCAP server on UDP/253 to allocate multicast address scopes.
Microsoft Windows Media Services (NetShow) has been deployed using MADCAP over UDP/253 to obtain multicast group addresses for streaming sessions.
Cisco IOS/IOS-XE supports a MADCAP client that queries UDP/253 to get multicast addresses for enterprise multicast applications (e.g., Cisco IP/TV).
Many firewalls (e.g., Check Point, Cisco ASA, Palo Alto) include a predefined “madcap (UDP/253)” service object used to permit this traffic in real deployments.

UDP 253