Discovering Duplicate Addresses Using NDP NS and NA
The NDP NS/NA messages also require hosts to do an important check to avoid using duplicate IPv6 addresses. IPv6 uses the Duplicate Address Detection (DAD) process before using a unicast address to make sure that no other node on that link is already using the address. If another host already uses that address, the first host simply does not use the address until the problem is resolved.
The term DAD refers to the function, but the function uses NDP NS and NA messages. Basically, a host sends an NS message, but it lists the address the host wants to use as the target address. If no duplicate exists, no other host should reply with an NA. However, if another host already uses that address, that ...
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