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Port 6633 (cisco-vpath-tun)

IANA assigns port 6633 to cisco-vpath-tun: Cisco vPath Services Overlay.

Registered (user) port, 1024-49151 UDP

Port 6633 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

IANA assignment

Service nameProtoDescriptionAssigneeReference
cisco-vpath-tun UDP Cisco vPath Services Overlay Cisco2 -

Registry dates for this port: registered 2012-06-11.

Check what is listening on port 6633

Linux: UDP 6633
sudo ss -ulnp 'sport = :6633'
Linux / macOS: which process owns the port
sudo lsof -nP -i :6633
Windows (Command Prompt)
netstat -ano | findstr :6633
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 6633

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 6633

Block port 6633 in the firewall

ufw
sudo ufw deny 6633/udp
iptables
sudo iptables -A INPUT -p udp --dport 6633 -j DROP
nftables
sudo nft add rule inet filter input udp dport 6633 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 6633' -Direction Inbound -Protocol UDP -LocalPort 6633 -Action Block

Related ports

6629nexgen-aux6632mxodbc-connect6634mpls-pm6635mpls-udp

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.