5351
Summary
- // if you see it open
- PCP mappings can enable incoming communications to reach hosts behind a NAT or firewall. Requests should be limited to authorized clients that are meant to control the relevant device.
- // common applications
- Creating mappings for incoming communicaReducing NAT keepalive traffic PCP clients send requests to a PCP server associated with a NAT or firewall device to manage mappings or optimize keepalive behavior. The evidence does not establish whether a particular network carries this traffic.
About port 5351/udp.
UDP port 5351 is assigned to the Port Control Protocol (PCP). PCP lets a host request control over how a NAT or simple firewall translates and forwards incoming packets, and can help reduce outgoing NAT keepalive traffic. The supplied evidence describes a protocol for managing packet forwarding through an upstream network device; it does not establish that any particular device has PCP enabled or is listening on this port.
PCP can create mappings that allow incoming communications to reach a host behind a NAT or firewall. Because those mappings can enable inbound access, PCP requests should be limited to clients authorized to control the relevant device. The RFC describes deployment with residential and carrier NATs and firewall devices, but the evidence does not establish a universal exposure policy for UDP 5351. Assess access according to the network's intended PCP clients and device configuration.
- Purpose
- PCP controls packet forwarding through NATs or simple firewalls and can optimize NAT keepalive traffic [Confirmed] — https://www.rfc-editor.org/rfc/rfc6887.txt
- Exposure
- Unknown; the supplied evidence does not establish whether this port is exposed. As editorial guidance, restrict PCP access to authorized clients. — https://www.rfc-editor.org/rfc/rfc6887.txt
- Risk
- PCP mappings can permit incoming traffic to reach hosts behind NATs or firewalls [Confirmed] — https://www.rfc-editor.org/rfc/rfc6887.txt
- IANA service name
- pcp [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv
- IANA description
- Port Control Protocol [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv
- IANA reference
- RFC 6887 [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv
Protocol purpose
Control packet forwarding through NATs or simple firewalls; optimize outgoing NAT keepalive messages
- Observed deployment or listener status
- Unknown [Unknown] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv
Service assignments.
| Name | Protocol | Description | Open frequency |
|---|---|---|---|
| nat-pmp | UDP | — | 0.33% |
| nat-pmp | TCP | pcp | 0.00% |
Service assignments from the IANA Service Name and Transport Protocol Port Number Registry, with open-frequency data from nmap-services.