Security & Authentication

Kerberos network authentication protocol administration port for authentication service management

Kerberos authentication protocol version 4 port for legacy Kerberos authentication

LDAP directory service port for directory information access

HTTPS alternative port for secure web services

UDP 4500 carries IPSec/IKEv2 NAT-Traversal (NAT-T). When a VPN client sits behind NAT, IKE negotiates a switch from port 500 to 4500 and encapsulates ESP traffic there. It almost always pairs with UDP 500.