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// Other services

Port 4191: Dual Stack MIPv6 NAT Traversal

Port 4191 is assigned by IANA to dsmipv6 (Dual Stack MIPv6 NAT Traversal).

4191

How dsmipv6 works

Other services
client:4191dsmipv6response client:4191dsmipv6response

The client sends a request to port 4191 and the dsmipv6 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 4191 dangerous?

We have no specific security note for port 4191. 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 4191

ServicePortTransportDescriptionReferenceUpdated
dsmipv6 4191 UDP Dual Stack MIPv6 NAT Traversal RFC 5555 -
-4191-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 4191, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4191'      # process listening on 4191
sudo lsof -nP -i :4191

macOS

sudo lsof -nP -i :4191

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4191 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4191
netstat -ano | findstr :4191

From another machine

nmap -p 4191 -sV <host>
sudo nmap -sU -p 4191 <host>
nc -zv <host> 4191

Block it in the firewall

sudo ufw deny 4191/udp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4191" -Direction Inbound -LocalPort 4191 -Protocol UDP -Action Block  # Windows
04 FAQ
What is port 4191 used for?

Port 4191 is assigned by IANA to dsmipv6 (Dual Stack MIPv6 NAT Traversal).

Is port 4191 TCP or UDP?

Port 4191 is registered for UDP.

Is it safe to open port 4191?

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 4191 is open?

On Linux run "ss -ltnup 'sport = :4191'", on macOS "lsof -nP -i :4191", and on Windows "netstat -ano | findstr :4191" to see the local process. From another machine, "nmap -p 4191 <host>" shows whether it is reachable.

05 Related
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