R21xx-HP FlexFabric 11900 Layer 3 IP Services Configuration Guide

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Figure 54 Address resolution
The address resolution procedure is as follows:
1. Host A multicasts an NS message. The source address of the NS message is the IPv6 address of the
sending interface of Host A and the destination address is the solicited-node multicast address of
Host B. The NS message body contains the link-layer address of Host A and the target IPv6
address.
2. After receiving the NS message, Host B determines whether the target address of the packet is its
IPv6 address. If yes, Host B learns the link-layer address of Host A, and then unicasts an NA
message containing its link-layer address.
3. Host A acquires the link-layer address of Host B from the NA message.
Neighbor reachability detection
After Host A acquires the link-layer address of its neighbor Host B, Host A can use NS and NA messages
to test reachability of Host B as follows:
1. Host A sends an NS message whose destination address is the IPv6 address of Host B.
2. If Host A receives an NA message from Host B, Host A decides that Host B is reachable. Otherwise,
Host B is unreachable.
Duplicate address detection
After Host A acquires an IPv6 address, it performs Duplicate Address Detection (DAD) to check whether
the address is being used by any other node (similar to gratuitous ARP in IPv4). DAD is accomplished
through NS and NA messages.
Figure 55 Duplicate address detection