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Port 15555 (cisco-snat)

IANA assigns port 15555 to cisco-snat: Cisco Stateful NAT.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
cisco-snat TCP Cisco Stateful NAT Kaushik Biswas -
cisco-snat UDP Cisco Stateful NAT Kaushik Biswas -

Registry dates for this port: registered 2006-03.

Check what is listening on port 15555

Linux: is anything listening on TCP 15555?
sudo ss -tlnp 'sport = :15555'
Linux: UDP 15555
sudo ss -ulnp 'sport = :15555'
Linux / macOS: which process owns the port
sudo lsof -nP -i :15555
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':15555 '
Windows (Command Prompt)
netstat -ano | findstr :15555
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 15555 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 15555
From Windows
Test-NetConnection HOST -Port 15555
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 15555

Block port 15555 in the firewall

ufw
sudo ufw deny 15555/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 15555 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 15555 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 15555' -Direction Inbound -Protocol TCP -LocalPort 15555 -Action Block
ufw
sudo ufw deny 15555/udp
iptables
sudo iptables -A INPUT -p udp --dport 15555 -j DROP
nftables
sudo nft add rule inet filter input udp dport 15555 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 15555' -Direction Inbound -Protocol UDP -LocalPort 15555 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.