What is duplicate address detection?

The IP Configuration Guide provides this description of duplicate address detection:

"Duplicate address detection is the process described in RFC 2462 which verifies that IPv6 home addresses are unique on the local link before assigning them to an interface. Duplicate address detection is performed on all IPv6 IPAQENET6 home addresses, whether they are manually configured or autogenerated, unless the INTERFACE statement specifies DUPADDRDET 0. Duplicate address detection is not done for LOOPBACK6 or VIRTUAL6 addresses. The duplicate address detection process sends a multicast neighbor solicitation and waits a period of time to see if another neighbor indicates that the address is in use. By default, only one neighbor solicitation is sent and the length of time waited is approximately one second. If no neighbor responds in that interval, the address is considered unique and the interface will start using it. The number of neighbor solicitations sent by duplicate address detection can be modified by the DUPADDRDET keyword on the INTERFACE statement. The duration of the wait interval (awaiting a response from a neighbor already using the address) can be modified by information obtained from routers on the attached network.

"Duplicate address detection occurs when the interface is started.....

"Prior to activation of the interface, manually configured addresses are shown in the Netstat HOME/-h report as unavailable with the reason DUPLICATE ADDRESS DETECTION PENDING. While the duplicated address detection is actively in progress for an address, the Netstat HOME/-h report shows the address as unavailable with the reason DUPLICATE ADDRESS DETECTION IN PROGRESS. If another neighbor indicates the address is in use during the duplicate address detection process, message EZZ9780I is issued and the address is not made available to the interface. If the address that was found to be in use is a manually configured address, the address appears in the Netstat HOME/-h report as unavailable with the reason DUPLICATE ADDRESS DETECTED."

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