Port 6635 (mpls-udp)

IANA assigns port 6635 to mpls-udp: Encapsulate MPLS packets in UDP tunnels..

Registered (user) port, 1024-49151 UDP

Port 6635 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

mpls-udp UDP Encapsulate MPLS packets in UDP tunnels. IESG RFC 7510

Registry dates for this port: registered 2015-02-10.

Linux: UDP 6635

sudo ss -ulnp 'sport = :6635'

Linux / macOS: which process owns the port

sudo lsof -nP -i :6635

Windows (Command Prompt)

netstat -ano | findstr :6635

Windows (PowerShell)

Get-NetUDPEndpoint -LocalPort 6635

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 6635

ufw

sudo ufw deny 6635/udp

iptables

sudo iptables -A INPUT -p udp --dport 6635 -j DROP

nftables

sudo nft add rule inet filter input udp dport 6635 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 6635' -Direction Inbound -Protocol UDP -LocalPort 6635 -Action Block

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