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// Other services

Port 15555: Cisco Stateful NAT

Port 15555 is assigned by IANA to cisco-snat (Cisco Stateful NAT).

15555

How cisco-snat works

Other services
client:15555cisco-snatresponse client:15555cisco-snatresponse

The client sends a request to port 15555 and the cisco-snat service answers.

Transport
TCP · 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 15555 dangerous?

We have no specific security note for port 15555. 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 15555

ServicePortTransportDescriptionReferenceUpdated
cisco-snat 15555 TCP, UDP Cisco Stateful NAT - 2006-03

// source: IANA service name and port number registry

03 Check it

Which program uses port 15555, and is it reachable?

Linux

sudo ss -ltnup 'sport = :15555'      # process listening on 15555
sudo lsof -nP -i :15555

macOS

sudo lsof -nP -i :15555

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 15555 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 15555
netstat -ano | findstr :15555

From another machine

nmap -p 15555 -sV <host>
sudo nmap -sU -p 15555 <host>
nc -zv <host> 15555

Block it in the firewall

sudo ufw deny 15555/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 15555" -Direction Inbound -LocalPort 15555 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 15555 used for?

Port 15555 is assigned by IANA to cisco-snat (Cisco Stateful NAT).

Is port 15555 TCP or UDP?

Port 15555 is registered for TCP and UDP.

Is it safe to open port 15555?

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 15555 is open?

On Linux run "ss -ltnup 'sport = :15555'", on macOS "lsof -nP -i :15555", and on Windows "netstat -ano | findstr :15555" to see the local process. From another machine, "nmap -p 15555 <host>" shows whether it is reachable.

05 Related
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