Port 67: DHCP Server
Hands out IP addresses on a local network (clients use port 68). Only meaningful on a local network. A rogue DHCP server on a shared VLAN can hijack other machines' traffic.
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Port 67 at a glance
Port67
ProtocolUDP
ServiceDHCP Server
Open to the Internet?No, keep it on a private network
See What Is Listeningss -lntup | grep ':67 '
Test From Outsidenmap -sU -p 67 your-server
Block with UFWufw deny 67/udp
Block with nftablesnft add rule inet filter input udp dport 67 drop
DHCP Server uses UDP port 67. Hands out IP addresses on a local network (clients use port 68).
Only meaningful on a local network. A rogue DHCP server on a shared VLAN can hijack other machines' traffic.
If ss shows something listening on port 67 on a public address, bind it to 127.0.0.1 or a private interface in the service's own configuration, and drop the port in the firewall as well.
Other Ports
20 FTP Data21 FTP22 SSH23 Telnet25 SMTP53 DNS67 DHCP Server80 HTTP110 POP3123 NTP143 IMAP161 SNMP389 LDAP443 HTTPS445 SMB465 SMTPS514 Syslog587 Mail Submission853 DNS over TLS993 IMAPS995 POP3S1194 OpenVPN1433 Microsoft SQL Server1900 SSDP / UPnP2049 NFS2083 cPanel (SSL)2087 WHM (SSL)3306 MySQL / MariaDB3389 RDP3478 STUN / TURN5060 SIP5432 PostgreSQL5900 VNC6379 Redis8006 Proxmox VE8080 HTTP Alternate8443 HTTPS Alternate11211 Memcached25565 Minecraft27017 MongoDB51820 WireGuard
Questions
What is port 67 used for?
DHCP Server. Hands out IP addresses on a local network (clients use port 68).
Is it safe to open port 67?
No, keep it on a private network. Only meaningful on a local network. A rogue DHCP server on a shared VLAN can hijack other machines' traffic.
How do I check if port 67 is open?
On the server, ss -lntup | grep ':67 ' shows what is listening. From another machine, nmap -sU -p 67 your-server shows whether the firewall lets it through.
How do I block port 67?
With UFW: ufw deny 67/udp. With nftables, add a drop rule for dport 67 in your input chain.
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