F3215-HP Load Balancing Module Network Management Configuration Guide-6PW101

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ICMPv6 messa

Function

Redirect message 137

Informs the source host of a better next hop on the path to a

particular destination when certain conditions are satisfied.

Address resolution

This function is similar to the ARP function in IPv4. An IPv6 node acquires the link-layer addresses of

neighboring nodes on the same link through NS and NA message exchanges. Figure 187 show

s how

Host A acquires the link-layer address of Host B on a single link.

Figure 187 Address resolution

The address resolution operates 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 contains the link-layer address of Host A.

2. After receiving the NS message, Host B determines whether the destination address of the packet

is its solicited-node multicast 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 check whether Host B is reachable.

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 the gratuitous ARP function in IPv4). DAD is

accomplished through NS and NA message exchanges. Figure 188

shows the DAD process.