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// Other services

Port 6636: Encapsulate MPLS packets in UDP tunnels with DTLS.

Port 6636 is assigned by IANA to mpls-udp-dtls (Encapsulate MPLS packets in UDP tunnels with DTLS.).

6636

How mpls-udp-dtls works

Other services
client:6636mpls-udp-dtlsresponse client:6636mpls-udp-dtlsresponse

The client sends a request to port 6636 and the mpls-udp-dtls service answers.

Transport
UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Other services
01 Security

Is port 6636 dangerous?

We have no specific security note for port 6636. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 6636

ServicePortTransportDescriptionReferenceUpdated
mpls-udp-dtls 6636 UDP Encapsulate MPLS packets in UDP tunnels with DTLS. RFC 7510 2015-02-10
-6636-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 6636, and is it reachable?

Linux

sudo ss -ltnup 'sport = :6636'      # process listening on 6636
sudo lsof -nP -i :6636

macOS

sudo lsof -nP -i :6636

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 6636 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 6636
netstat -ano | findstr :6636

From another machine

nmap -p 6636 -sV <host>
sudo nmap -sU -p 6636 <host>
nc -zv <host> 6636

Block it in the firewall

sudo ufw deny 6636/udp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 6636" -Direction Inbound -LocalPort 6636 -Protocol UDP -Action Block  # Windows
04 FAQ
What is port 6636 used for?

Port 6636 is assigned by IANA to mpls-udp-dtls (Encapsulate MPLS packets in UDP tunnels with DTLS.).

Is port 6636 TCP or UDP?

Port 6636 is registered for UDP.

Is it safe to open port 6636?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Close the port if nothing on the host needs it.

How do I check if port 6636 is open?

On Linux run "ss -ltnup 'sport = :6636'", on macOS "lsof -nP -i :6636", and on Windows "netstat -ano | findstr :6636" to see the local process. From another machine, "nmap -p 6636 <host>" shows whether it is reachable.

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