2 entries are registered on port 753. It is a well-known port (0–1023) — assignments here are IANA's, and a service found on one is usually the service that was assigned it.
services registered on this number
2 transports in use
entries encrypted on the wire
1 of 2 iana-registered
| port | service | proto | category | risk | views |
|---|---|---|---|---|---|
| :753 | Kerberos User Registration | UDP | Security | safe | 8.5k |
| :753 | Reverse Routing Header (RRH) | TCP | Network Services | caution | 5.8k |
Port 753 is primarily associated with the Kerberos user registration server (userreg_server). It facilitates client-server communication for managing user identity registrations within Kerberos authentication infrastructure. Typically using UDP, it plays a role in updating and maintaining secure user credentials essential for the operation of Kerberos-based networks.
port 753 as Kerberos User Registration →Port 753 is assigned for the Reverse Routing Header (RRH) protocol, which facilitates advanced routing control for IP packets. It's primarily used in experimental or specialized network environments that require customized packet routing and is an official, unencrypted control protocol operating mainly over TCP.
port 753 as Reverse Routing Header (RRH) →The registry says what 753 is registered to. What is listening on it right now is decided by the host, and only the host can be asked. Each of these prints the process behind the socket.
ss -ltnp | grep ':753\b'lsof -nP -iTCP:753 -sTCP:LISTENnetstat -ano | findstr :753On Linux and Windows the process name comes back with the socket; on macOS lsof needs sudo to name a process that isn't yours. Match what it prints against the 2 entries above.
A port number is not a service. Anything may listen on 753 — what you actually met is decided by the host, not the registry. If a service is missing here, it belongs in the registry.
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