Address resolution, Neighbor unreachability detection, Duplicate address detection – H3C Technologies H3C S3100 Series Switches User Manual

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1-6

H3C S3100 Series Ethernet Switches do not support RS, RA, or Redirect message.

Of the above mentioned IPv6 NDP functions, H3C S3100 Series Ethernet Switches support the

following three functions: address resolution, neighbor unreachability detection, and duplicate

address detection. The subsequent sections present a detailed description of these three functions

and relevant configuration.

The NDP mainly provides the following functions:

Address resolution

Similar to the ARP function in IPv4, a node acquires the link-layer address of neighbor nodes on the

same link through NS and NA messages.

Figure 1-3

shows how node A acquires the link-layer address

of node B.

Figure 1-3 Address resolution

The address resolution procedure is as follows:

1) Node A multicasts an NS message. The source address of the NS message is the IPv6 address of

the interface of node A and the destination address is the solicited-node multicast address of node

B. The NS message contains the link-layer address of node A.

2) After receiving the NS message, node B judges whether the destination address of the packet is

the corresponding solicited-node multicast address of its own IPv6 address. If yes, node B learns

the link-layer address of node A and returns an NA message containing the link-layer address of

node B in the unicast mode.

3) Node A acquires the link-layer address of node B from the NA message. After that, node A and

node B can communicate with each other.

Neighbor unreachability detection

After node A acquires the link-layer address of its neighbor node B, node A can verify whether node B is

reachable according to NS and NA messages.

1) Node A sends an NS message whose destination address is the IPv6 address of node B.

2) If node A receives an NA message from node B, node A considers that node B is reachable.

Otherwise, node B is unreachable.

Duplicate address detection

After a node acquires an IPv6 address, it should perform the duplicate address detection to determine

whether the address is being used by other nodes (similar to the gratuitous ARP function). The