Port 547 (DHCPv6 server)

DHCPv6 servers and relays listen on UDP 547.

Well-known (system) port, 0-1023 UDP Network infrastructure Localhost or LAN only

Port 547 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

What port 547 is used for

DHCPv6 servers and relays listen on UDP 547.

Localhost or LAN only. Rogue DHCPv6 (mitm6) is a common Windows network attack; use DHCPv6 Guard or disable IPv6 DHCP where not used.

Service nameProtoDescriptionAssigneeReference

dhcpv6-server TCP DHCPv6 Server IESG RFC 5460

dhcpv6-server UDP DHCPv6 Server IESG RFC 9915

Registry dates for this port: last modified 2018-05-21.

Linux: UDP 547

sudo ss -ulnp 'sport = :547'

Linux / macOS: which process owns the port

sudo lsof -nP -i :547

Windows (Command Prompt)

netstat -ano | findstr :547

Windows (PowerShell)

Get-NetUDPEndpoint -LocalPort 547

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

nc -vzu -w 5 HOST 547

ufw

sudo ufw deny 547/udp

iptables

sudo iptables -A INPUT -p udp --dport 547 -j DROP

nftables

sudo nft add rule inet filter input udp dport 547 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 547' -Direction Inbound -Protocol UDP -LocalPort 547 -Action Block

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