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Chapter 6 Neighbor Discovery At the end of this chapter,you should be able to do the following: ■Describe the functions of the Neighbor Discovery(ND)protocol. ■List and describe the function and format of ND options. ■List and describe the function and format of ND messages. ■Describe which ND messages use which ND options. Describe the details of the address resolution,neighbor unreachability detection, duplicate address detection,router discovery,and redirect processes. Describe the host sending algorithm in terms of host data structures and ND messages. Neighbor Discovery Overview Internet Protocol version 6 (IPv6)Neighbor Discovery (ND)is a set of messages and pro- cesses defined in RFC 4861 that determine relationships between neighboring nodes.ND replaces Address Resolution Protocol (ARP),Internet Control Message Protocol (ICMP) router discovery,and the ICMP Redirect message used in IPv4.ND also provides additional functionality. ND is used by nodes to do the following: Resolve the link-layer address of a neighboring node to which an IPv6 packet is being forwarded. ■Determine when the link-layer address of a neighboring node has changed ■Determine whether a neighbor is still reachable. ND is used by hosts to do the following: ■Discover neighboring routers. ■Autoconfigure addresses,address prefixes,routes,and other configuration parameters. ND is used by routers to do the following: ■Advertise their presence,host configuration parameters,routes,and on-link prefixes. Inform hosts of a better next-hop address to forward packets for a specific destination. 123 ! "# $ %& '( ) * # *+ , %,+ ! ++ -" ./ 0 12345672 892 :;<486=<3 =: 892 >26?97=5 1634=@25A B>1C D5=8=4=EF 0 G638 H<I I2345672 892 :;<486=< H<I :=5JH8 =: >1 =D86=<3F 0 G638 H<I I2345672 892 :;<486=< H<I :=5JH8 =: >1 J233H?23F 0 12345672 K9649 >1 J233H?23 ;32 K9649 >1 =D86=<3F 0 12345672 892 I28H6E3 =: 892 HII5233 523=E;86=<L <26?97=5 ;<52H49H76E68A I282486=<L I;DE64H82 HII5233 I282486=<L 5=;825 I634=@25AL H<I 52I65248 D5=423323F 0 12345672 892 9=38 32<I6<? HE?=5689J 6< 825J3 =: 9=38 IH8H 385;48;523 H<I >1 J233H?23F MN OPQRSPRQ TSUQUVUW XRSYZUP [ \OTX[] ^RZ_`aUS bZYVUXRSc \^b] ZY d YRQ Ue fRYYd_RY dPg hSUi VRYYRY gReZPRg ZP jkl mn[o Q`dQ gRQRSfZPR SRWdQZUPY`ZhY aRQpRRP PRZ_`aUSZP_ PUgRYq ^b SRhWdVRY rggSRYY jRYUWsQZUP TSUQUVUW \rjT]t OPQRSPRQ lUPQSUW uRYYd_R TSUQUVUW \OluT] SUsQRS gZYVUXRSct dPg Q`R OluT jRgZSRVQ fRYYd_R sYRg ZP OTXmq ^b dWYU hSUXZgRY dggZQZUPdW esPVQZUPdWZQcq ^b ZY sYRg ac PUgRY QU gU Q`R eUWWUpZP_v 0 jRYUWXR Q`R WZPwiWdcRS dggSRYY Ue d PRZ_`aUSZP_ PUgR QU p`ZV` dP OTX[ hdVwRQ ZY aRZP_eUSpdSgRgq 0 bRQRSfZPR p`RP Q`R WZPwiWdcRS dggSRYY Ue d PRZ_`aUSZP_ PUgR `dY V`dP_Rgq 0 bRQRSfZPR p`RQ`RS d PRZ_`aUS ZY YQZWW SRdV`daWRq ^b ZY sYRg ac `UYQY QU gU Q`R eUWWUpZP_v 0 bZYVUXRS PRZ_`aUSZP_ SUsQRSYq 0 rsQUVUPeZ_sSR dggSRYYRYt dggSRYY hSReZxRYt SUsQRYt dPg UQ`RS VUPeZ_sSdQZUP hdSdfRQRSYq ^b ZY sYRg ac SUsQRSY QU gU Q`R eUWWUpZP_v 0 rgXRSQZYR Q`RZS hSRYRPVRt `UYQ VUPeZ_sSdQZUP hdSdfRQRSYt SUsQRYt dPg UPiWZPw hSReZxRYq 0 OPeUSf `UYQY Ue d aRQQRS PRxQi`Uh dggSRYY QU eUSpdSg hdVwRQY eUS d YhRVZeZV gRYQZPdQZUPq