# WHATPORT(111)

## NAME

port 111 — sunrpc / rpcbind (portmapper) — The ONC RPC portmapper — ask it which port a given RPC program is on, and it tells you.

Protocol: TCP/UDP  
IANA registry

## DESCRIPTION

rpcbind (formerly portmap) maps ONC RPC program numbers to the ports their servers actually listen on, per RFC 1833. NFS, `mountd`, `statd`, NIS, and quota daemons register with it at startup, and clients query 111 first to find them — which is exactly what `rpcinfo -p` does. It is on by default on most Linux and Solaris NFS servers and answers on both TCP and UDP. Its UDP side has been abused as a DDoS reflector, and its dump reply is a free inventory of a host's RPC services.

## EXPOSURE

**Do not expose.** An internet-facing rpcbind enumerates your RPC services to anyone and its UDP listener is a known amplification reflector. Keep it on the internal network.

## CHECK

```sh
rpcinfo -p TARGET
```

## SEE ALSO

- spec — [RFC 1833 — Binding Protocols for ONC RPC Version 2](https://www.rfc-editor.org/rfc/rfc1833.html) (rfc-editor.org)
- docs — [rpcbind(8) manual page](https://man7.org/linux/man-pages/man8/rpcbind.8.html) (man7.org)
- spec — [RFC 4506 — XDR: External Data Representation Standard](https://www.rfc-editor.org/rfc/rfc4506.html) (rfc-editor.org)
- iana — [IANA Service Name and Transport Protocol Port Number Registry](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml) (iana.org)

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HTML: <https://whatport.net/111/> · JSON: <https://whatport.net/111.json> · full dataset: <https://whatport.net/ports.json>