DAD Overview

When enabled on a user VR or VR-Default, the DAD feature checks all IP addresses configured on the DAD-enabled VRs to determine if there are duplicate IP addresses on the networks connected to the switch. If a duplicate address is discovered, the switch does one of the following:
  • Marks the IP address as valid
  • Marks the IP address as duplicate and generates EMS events to advertise this

At the completion of the DAD check for each interface, the interface is marked valid or duplicate. A valid IP interface can be used by all switch processes for IP communications. There are no restrictions on a valid IP address. If no duplicate address is detected, the IP address is marked valid.

A duplicate IP address cannot be used for IP communications. If a duplicate IP address is detected, the marking depends on the action that initiated the test and can depend on a previous marking for the IP address. For some events, a duplicate IP address generates an EMS event, and for some other events, a duplicate IP address results in a disabled IP address and corresponding EMS events.