# WHATPORT(254)

## NAME

port 254 — Unassigned — No registered service — IANA has never assigned 254, yet scanners still probe it by habit.

Protocol: TCP  
IANA registry

## DESCRIPTION

The IANA service name and port number registry has no entry for 254 on TCP or UDP; it sits in a gap between 250 and 255 that was never handed out. Nmap's empirical service list labels it plainly "unknown" while still ranking it inside the default top-1000 scan set, which is why it appears in scan output at all. Anything actually listening here is a local choice by whoever configured the host, not a protocol you can infer from the number. Treat an open 254 as a prompt to fingerprint the service, never as an identification.

## EXPOSURE

**Expose with care.** An open port with no registered protocol tells you nothing about what it is — identify the listener with a service probe before deciding whether it belongs on a public IP.

## CHECK

```sh
nmap -sV -p 254 TARGET
```

## SEE ALSO

- iana — [IANA Service Name and Transport Protocol Port Number Registry — 254](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=254) (iana.org)
- source — [nmap-services — the empirical port frequency list (254/tcp "unknown")](https://github.com/nmap/nmap/blob/master/nmap-services) (github.com)

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HTML: <https://whatport.net/254/> · JSON: <https://whatport.net/254.json> · full dataset: <https://whatport.net/ports.json>