User`s guide

VRRP Configuration Notes
9-18 Configuring VRRP
•Defaultbackuprouterpriority=100
•Master‐down‐interval=timeittakesabackuptodetectthemasterisdown
–=(3*adv‐interval)+skew‐time
–=(3*1second)+((256‐100)/256)
–=3.6seconds
When the Master Reboots or Is Down
Ifamasterrouterismanuallyrebooted,orifitsinterfaceismanuallybroughtdown,itwillsenda
specialkeep‐aliveadvertisementthatletsthebackuproutersknowthatanewmasterisneeded
immediately.
Determining a Virtual MAC Address
AvirtualrouterwillrespondtoARPrequestswithavirtualMACaddress.ThisvirtualMAC
dependsonthevirtualrouterID:
virtualMACaddress=00005E:0001XX
whereXXisthevirtualrouterID
ThisvirtualMACaddressisalsousedasthesourceMACaddressofthekeep‐alive
Advertisementstransmitted
bythemasterrouter.
•TheseMACaddresses,whenactive,useentriesintheport’sRoutingAddressTable(RAT).
SincetheRAThaseightentriesandotherresourcesalsousetheRAT,thesystemwilllimitthe
numberofuniquevirtualroutingID’stosixorfeweronaperportbasis.
–Ifmultiplevirtualroutersarecreatedonasingleinterface,thevirtualroutersmusthave
uniqueidentifiers.Ifvirtualroutersarecreatedondifferentinterfaces,youcanreuse
virtualrouterIDs.
–AsspecifiedinRFC2338,abackuprouterthathastransitionedtomasterwillnotrespond
topings,accepttelnet
sessions,orfieldSNMPrequestsdirectedatthevirtualrouter’sIP
address.Notrespondingallowsnetworkmanagementtonoticethattheoriginalmaster
router(thatis,theIPaddressowner)isdown.
Note: In some instances, a heavy load on a VRRP master may delay VRRP packet transmission
and cause the backup router to assume the role of master.