ZyXEL Communications GS2210-24, Руководство пользователя

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Appendix C IPv6
GS2210 Series User’s Guide
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such as t he syst em nam e. The int er face- I D opt ion pr ov ides slot num ber, por t infor m at ion and t he
VLAN I D t o t he DHCPv6 server. The r em ot e- I D opt ion ( if any) is st r ipped fr om t he Relay- Reply
m essages befor e t he r elay agent sends t he packet s t o t he client s. The DHCP ser ver copies t he
int er face- I D opt ion fr om t he Relay- For war d m essage int o t he Relay- Reply m essage and sends it t o
t he r elay agent . The int er face- I D should not change even aft er t he r elay agent r est ar t s.
Prefix Delegation
Pr efix delegat ion enables an I Pv6 r out er t o use t he I Pv6 pr efix ( net w or k addr ess) r eceived fr om t he
I SP ( or a connect ed uplink rout er ) for it s LAN. The Swit ch uses t he r eceived I Pv6 pr efix ( for
exam ple, 2001: db2: : / 48) t o generat e it s LAN I P addr ess. Thr ough sending Rout er Adver t isem ent s
( RAs) r egular ly by m ult icast , t he Sw it ch passes t he I Pv6 pr efix infor m at ion t o it s LAN host s. The
host s t hen can use t he pr efix t o generat e t heir I Pv6 addr esses.
ICMPv6
I nt er net Cont r ol Message Pr ot ocol for I Pv6 ( I CMPv6 or I CMP for I Pv6) is defined in RFC 4443.
I CMPv6 has a pr eceding Next Header value of 58, w hich is differ ent fr om t he value used t o ident ify
I CMP for I Pv4. I CMPv6 is an int egral par t of I Pv6. I Pv6 nodes use I CMPv6 t o r epor t er r or s
encount er ed in packet pr ocessing and per for m ot her diagnost ic funct ions, such as " ping" .
Neighbor Discovery Protocol (NDP)
The Neighbor Discover y Pr ot ocol ( NDP) is a pr ot ocol used t o discover ot her I Pv6 devices and t rack
neighbor ’s r eachabilit y in a net w or k. An I Pv6 device uses t he follow ing I CMPv6 m essages t ypes:
• Neighbor solicit at ion: A r equest fr om a host t o deter m ine a neighbor ’s link- layer addr ess ( MAC
address) and det ect if t he neighbor is st ill r eachable. A neighbor being “ r eachable” m eans it
r esponds t o a neighbor solicit at ion m essage ( fr om t he host ) w it h a neighbor adver t isem ent
m essage.
• Neighbor adver t isem ent : A r esponse from a node t o announce it s link- layer addr ess.
• Rout er solicit at ion: A r equest fr om a host t o locate a rout er t hat can act as t he default r out er and
for ward packet s.
• Rout er advert isem ent : A r esponse t o a r out er solicit at ion or a per iodical m ult icast adver t isem ent
fr om a r out er t o adver t ise it s pr esence and ot her param et er s.
IPv6 Cache
An I Pv6 host is r equir ed t o have a neighbor cache, dest inat ion cache, pr efix list and default r out er
list . The Sw it ch m aint ains and updat es it s I Pv6 caches const ant ly using t he inform at ion from
r esponse m essages. I n I Pv6, t he Sw it ch configur es a link- local addr ess aut om at ically, and t hen
sends a neighbor solicit at ion m essage t o check if t he addr ess is unique. I f t her e is an addr ess t o be
r esolved or ver ified, t he Sw it ch also sends out a neighbor solicit at ion m essage. When t he Sw it ch
r eceives a neighbor adver t isem ent in r esponse, it st or es t he neighbor ’s link- layer addr ess in t he
neighbor cache. When t he Sw it ch uses a r out er solicit at ion m essage t o quer y for a r out er and
r eceives a r out er adver t isem ent m essage, it adds t he r out er ’s infor m at ion t o t he neighbor cache,
pr efix list and dest inat ion cache. The Sw it ch cr eat es an ent r y in t he default r out er list cache if t he
r out er can be used as a default r out er.
When t he Sw it ch needs t o send a packet , it fir st consult s t he dest inat ion cache t o det er m ine t he
next hop. I f t her e is no m at ching ent r y in t he dest inat ion cache, t he Sw it ch uses t he pr efix list t o