DHCP: Port 546 (DHCP Client port for IPv6) should not be used by any other process while rogue detection is enabled

Applies To: Windows Server 2008 R2, Windows Server 2012

This topic is intended to address a specific issue identified by a Best Practices Analyzer scan. You should apply the information in this topic only to computers that have had the Dynamic Host Configuration Protocol Best Practices Analyzer run against them and are experiencing the issue addressed by this topic. For more information about best practices and scans, see Best Practices Analyzer (https://go.microsoft.com/fwlink/?LinkId=122786).

Port 546 is in use by another process.

If port 546 is in use by another process, DHCP server cannot perform rogue DHCP server detection in IPv6.

Configure the conflicting process to use a different port and DHCP to use port 546.

DHCP uses UDP ports 546 and 547 to initiate communication between the IPv6 client and server. If either of these ports is in use by another application, or the ports are otherwise reserved, DHCP will not function. You can use Windows Firewall with Advanced Security (WFAS) with the following procedure to reassign ports so that DHCP can use port 546.

To perform this procedure, you must be a member of the Administrators group, or you must have been delegated the appropriate authority.

1. Click Start, click Administrative tools, and then click Windows Firewall with Advanced Security.

2. Click Inbound rules.

3. In the Local Port column, right-click 546 and then click Properties.

4. Click Protocols and Port, specify a port other than 546 in Local Port, and then click OK.

5. Click Action, click New Rule…, and then click Predefined.

6. Click DHCP Server, check all of the DHCP rules, click Next and then click Finish.

For updated detailed IT pro information about DHCP, see the Windows Server 2008 R2 documentation on the Microsoft TechNet Web site.