Port 647

dhcp-failover · TCP/UDP

RangeSystem/well-known port (0–1023)
ProtocolTCP/UDP
Servicedhcp-failover
ReferenceRFC 8156
Modified2018-05-21

Frequently asked questions

What is port 647 used for?

Port 647 is registered with the IANA for dhcp-failover (TCP/UDP). Description: DHCP Failover.

Is port 647 a well-known port?

Yes. Port 647 is in the range 0–1023 (system or well-known ports). On Linux and macOS only privileged processes may bind to these ports.

How do I check whether port 647 is open?

Locally on Linux with ss -tulpn | grep ':647\b', on Windows with netstat -ano | findstr :647. To test a remote host use Test-NetConnection <host> -Port 647 in PowerShell or nc -zv <host> 647 on Linux/macOS.

How do I open port 647 in the firewall?

Ubuntu/Debian (ufw): sudo ufw allow 647/tcp. Fedora/RHEL (firewalld): sudo firewall-cmd --add-port=647/tcp --permanent, then firewall-cmd --reload. Windows (PowerShell as administrator): New-NetFirewallRule -DisplayName "Port 647" -Direction Inbound -Protocol TCP -LocalPort 647 -Action Allow.

IANA registry entries

ProtocolServiceDescription (IANA)
TCPdhcp-failoverDHCP Failover
UDPdhcp-failoverDHCP Failover

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