530 CHAPTER 46: IPV 6 MANGEMENT CONFIGURATIONn ■ 3Com Switch 4210 Family do not support RS, RA, or Redirect message.■ Of the above mentioned IPv6 NDP functions, 3Com Switch 4210 Familysupport the following three functions: address resolution, neighborunreachability detection, and duplicate address detection. The subsequentsections present a detailed description of these three functions and relevantconfiguration.The NDP mainly provides the following functions:Address resolutionSimilar to the ARP function in IPv4, a node acquires the link-layer address ofneighbor nodes on the same link through NS and NA messages. Figure 191 showshow node A acquires the link-layer address of node B.Figure 191 Address resolutionThe address resolution procedure is as follows:1 Node A multicasts an NS message. The source address of the NS message is theIPv6 address of the interface of node A and the destination address is theNeighbor advertisement (NA)messageUsed to respond to a neighbor solicitation messageWhen the link layer address changes, the local node initiates aneighbor advertisement message to notify neighbor nodes ofthe change.Router solicitation (RS)messageAfter started, a host sends a router solicitation message torequest the router for an address prefix and other configurationinformation for the purpose of autoconfiguration.Router advertisement (RA)messageUsed to respond to a router solicitation messageWith the RA message suppression disabled, the router regularlysends a router advertisement message containing informationsuch as address prefix and flag bits.Redirect message When a certain condition is satisfied, the default gateway sendsa redirect message to the source host so that the host canreselect a correct next hop router to forward packets.Table 385 Types and functions of ICMPv6 messagesICMPv6 message FunctionSrc=ADst=solicited- node multicast of BICMP type=136Src=BDst=AData=link- layer address of BNSNAA BICMP type=135Data=link- layer address of A
