524 CN4093 Application Guide for N/OS 8.4
VRRP Components
EachphysicalrouterrunningVRRP isknownasaVRRProuter .
Virtual Router
TwoormoreVRRProuterscanbeconfiguredtoformavirtualrouter(RFC2338).
EachVRRProutermayparticipateinoneormorevirtualrouters.Eachvirtual
routerconsistsofauser‐configuredvirtualrouteridentifier(VRID)andanIPv4
address.
Virtual Router MAC Address
TheVRIDisusedtobuildthevirtualrouterMACAddress.Thefivehighest‐order
octetsofthevirtualrouterMACAddressarethestandardMACprefix
(00‐00‐5E‐00‐01)definedinRFC2338.TheVRIDisusedtoformthelowest‐order
octet.
Owners and Renters
OnlyoneoftheVRRProutersinavirtualroutermaybeconfiguredastheIPv4
addressowner.Thisrouterhasthevirtualrouter’sIPv4addressasitsrealinterface
address.Thisrouterrespondstopacketsaddressedtothevirtualrouter’sIPv4
addressforICMPpings,TCPconnections,andsoon.
ThereisnorequirementforanyVRRProutertobetheIPv4addressowner.Most
VRRPinstallationschoosenottoimplementanIPv4addressowner.Forthe
purposesofthischapter, V RRProutersthatarenottheIPv4addressownerare
calledrenters.
Master and Backup Virtual Router
Withineachvirtualrouter,oneVRRProuterisselectedtobethevirtualrouter
master.See“SelectingtheMasterVRRPRouter”onpage 525foranexplanationof
theselectionprocess.
Note: IftheIPv4addressownerisavailable,itwillalwaysbecomethevirtual
routermaster.
Thevirtualroutermasterforwardspackets
senttothevirtualrouter.Italso
respondstoAddressResolutionProtocol(ARP)requestssenttothevirtualrouterʹs
IPv4address.Finally,thevirtualroutermastersendsoutperiodicadvertisements
toletotherVRRProutersknowitisaliveanditspriority.
Withinavirtualrouter,theVRRProutersnot
selectedtobethemasterareknown
asvirtualrouterbackups.Shouldthevirtualroutermasterfail,oneofthevirtual
routerbackupsbecomesthemasterandassumesitsresponsibilities.
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