Port 67 (DHCP server (BOOTP))

DHCP servers listen on UDP 67 and hand out IP addresses, gateways and DNS servers; PXE boot also starts here.

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

Port 67 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

What port 67 is used for

DHCP servers listen on UDP 67 and hand out IP addresses, gateways and DNS servers; PXE boot also starts here.

Localhost or LAN only. LAN only. A rogue DHCP server on a network can redirect all traffic; enable DHCP snooping on managed switches.

Service nameProtoDescriptionAssigneeReference

bootps TCP Bootstrap Protocol Server
Defined TXT keys: None Bill Croft RFC 951

bootps UDP Bootstrap Protocol Server - -

Linux: UDP 67

sudo ss -ulnp 'sport = :67'

Linux / macOS: which process owns the port

sudo lsof -nP -i :67

Windows (Command Prompt)

netstat -ano | findstr :67

Windows (PowerShell)

Get-NetUDPEndpoint -LocalPort 67

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

nc -vzu -w 5 HOST 67

ufw

sudo ufw deny 67/udp

iptables

sudo iptables -A INPUT -p udp --dport 67 -j DROP

nftables

sudo nft add rule inet filter input udp dport 67 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 67' -Direction Inbound -Protocol UDP -LocalPort 67 -Action Block

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