Port 547: DHCPv6 server
Port 547 is the DHCPv6 server port, over UDP. It is the IPv6 counterpart of port 67: clients send solicit and request messages to it, using the multicast address ff02::1:2 rather than a broadcast, and replies go back to port 546.
| Port number | 547 |
|---|---|
| Service | DHCPv6 server |
| Protocol | UDP |
| Category | Core services |
| Default encryption | No |
| IANA service name | dhcpv6-server |
| IANA transports | TCP, UDP |
| Used in practice | UDP |
Which ports are related to port 547?
The port a reader usually needs next is the encrypted or plaintext twin of this one, so those are listed first rather than buried in a generic list.
What commonly listens on port 547?
- ISC Kea and ISC DHCP with DHCPv6 enabled
- dnsmasq on routers
- The DHCP Server role on Windows Server, scoped for IPv6
How do I check whether port 547 is open?
Port 547 is UDP, which changes the answer: there is no handshake to complete, so nothing outside the host can prove the port is open. Asking the host itself is the reliable route.
| Question | Command | What to know |
|---|---|---|
| Is it open on a remote host? | sudo nmap -sU -p 547 example.com | UDP has no handshake, so there is nothing to complete. nmap infers the state from whether an ICMP port-unreachable comes back, needs root, and is slow and easy to misread. A silent port may be open, filtered, or simply not replying to a probe it does not recognise. |
| What is listening locally? | ss -ulnp | grep ':547 ' | Shows the UDP socket bound to port 547. This is the reliable way to answer the question, because you are asking the host itself rather than guessing from outside. |
Replace example.com with the host you are testing. A blocked port and a port with nothing listening on it look identical from the outside, so if a service should be running, check locally before blaming the firewall.
Frequently asked questions
What is the difference between port 547 and port 67?
They do the same job for different address families. Port 67 is the IPv4 DHCP server port and port 547 is the DHCPv6 server port. A network running both needs firewall rules for both pairs, 67 and 68 for IPv4 and 546 and 547 for IPv6.
Do I need DHCPv6 if my network already has router advertisements?
Not always. IPv6 hosts can build their own address from a router advertisement using stateless autoconfiguration, with no DHCPv6 server involved. DHCPv6 on port 547 is used when you want assigned addresses, or need to hand out options such as DNS servers in environments where the router advertisement route is not enough.
What is port 547 used for?
Port 547 is the DHCPv6 server port, over UDP. It is the IPv6 counterpart of port 67: clients send solicit and request messages to it, using the multicast address ff02::1:2 rather than a broadcast, and replies go back to port 546.
Is port 547 TCP or UDP?
IANA assigns port 547 on TCP, UDP. In practice it carries UDP. The TCP registration is unused. DHCPv6 is UDP only.
Is port 547 secure?
Port 547 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 547 on my firewall?
Only if you specifically need DHCPv6 server. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.