Port 67 / UDP
DHCP Server
Port 67 – DHCP Server Protocol Specification
Technical analysis, security advisories, vulnerability mitigation, and firewall syntax for TCP/UDP port 67 (DHCP Server).
Port Number
67
Transport Protocol
UDP
Port Range Type
Well-Known (0-1023)
Default Status
Restricted / LAN
Service Description & Architectural Context
Dynamic Host Configuration Protocol server endpoint.
IANA / RFC Designation:
Port 67 is assigned to DHCP Server under the Internet Assigned Numbers Authority (IANA) service name registry. In enterprise infrastructure and homelab setups, services listening on this port must follow the principle of least privilege.
Security Analysis & Attack Surface Assessment
Confine to local broadcast domain. Use DHCP snooping to prevent rogue servers.
Hardening Recommendations:
- Do not expose port 67 to public WAN interfaces unless authenticated TLS or VPN wrapping is strictly enforced.
- Enforce rate-limiting using Fail2ban, CrowdSec, or cloud edge DDoS protection.
- Audit active listening sockets locally:
ss -tulpn | grep :67ornetstat -ano | findstr :67.
Firewall Rule Snippets for Port 67
UFW (Ubuntu / Debian Linux)
sudo ufw allow 67/udp
iptables (Standard Linux Kernel)
sudo iptables -A INPUT -p udp --dport 67 -j ACCEPT
Windows PowerShell (Defender Advanced Firewall)
New-NetFirewallRule -DisplayName "Allow Port 67" -Direction Inbound -LocalPort 67 -Protocol UDP -Action Allow