Port 6634 (mpls-pm)

IANA assigns port 6634 to mpls-pm: MPLS Performance Measurement out-of-band response.

Registered (user) port, 1024-49151 UDP

Port 6634 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-pm UDP MPLS Performance Measurement out-of-band response Cisco Systems 2 -

Registry dates for this port: registered 2014-02-20.

Linux: UDP 6634

sudo ss -ulnp 'sport = :6634'

Linux / macOS: which process owns the port

sudo lsof -nP -i :6634

Windows (Command Prompt)

netstat -ano | findstr :6634

Windows (PowerShell)

Get-NetUDPEndpoint -LocalPort 6634

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

nc -vzu -w 5 HOST 6634

ufw

sudo ufw deny 6634/udp

iptables

sudo iptables -A INPUT -p udp --dport 6634 -j DROP

nftables

sudo nft add rule inet filter input udp dport 6634 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 6634' -Direction Inbound -Protocol UDP -LocalPort 6634 -Action Block

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