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FHRP

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beef410's version from 2018-05-20 23:17

HSRP v1

Question Answer
FHRPFirst Hop Redundancy Protocol, HSRP and VRRP
HSRPHot-Standby Redundancy Protocol - Cisco proprietary RFC 2281
Active RouterThe in-use router
Standby RouterThe router ready to step in
Active/StandbyOnly refers to HSRP status, not routing status. IE router is still being a normal router in addition to HSRP duties.
PseudorouterThe virtual router that devices treat at default gateway.
(config-if)#standby <grp#> ip <ip>Enable HSRP on the interface, apply to client facing interfaces
Virtual MAC0000.0c07.acXX is reserved for HSRP, last 2 is group number in hex
Default timershello 3s, hold/dead time 10s. Cannot set hold time < hello time router won't let you do it.
PriorityDefault 100, higher is better -> IP address
PreemptionAllows rebooting router to take back active role when it has higher priority, default off.
(config-if)#standby <grp3> preemptenable preemption, can specify delay to reload.
Multicast224.0.0.2
3routers3rd router will stay in Listen state until one of the active or standby routers goes down
Router v PortIf a port goes down tracking must be setup for a redundant HSRP setup to fail-over. Whereas if the router itself dies fail-over will occur without tracking.
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HSRP v2

Question Answer
(config-if)#standby versionSelect v1 or v2
Duplicate AddrDifferent versions maintain different groups, v1 grp1 and v2 grp1 are in different groups and will cause a duppaddr error
Virtual Mac0000.0c9f.fXXX where XXX is group number in hex
Group numbersinstead of 255, 4095groups
IPv6v2 supports IPv6, v1 does not
Multicast224.0.0.102
Timersv2 supports millisecond timers
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Show Commands

Question Answer
sh standby briefInt/grp/priority/preemption/state/active/standby/virtual IP. Everything not related to macs/timers
sh standbyThe HSRP show command, all relevant info, shows all groups. Grp/state/virtualip/mac/active+standbyrouters and state change timer/count
sh hsrpSame thing as show standby except only HSRP.
sh vrrpShow VRRP info, virtual ip/mac, preemption, ad interval, priority, master priorities, no backup
sh vrrp briefVRRP relevant info , no backup listing
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Troubleshoot

Question Answer
Same subnetvirtual ip should be in the same network as the hosts its servicing. router will warn but allow back IP
DuplicateIf two HSRP groups are using the same IP console will error
TimersMust be set on the Active router, sh standby will show local config but won't come into effect unless local router becomes active
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States

Question Answer
DisabledNot mentioned in show standby, disabled state HSRP is off
InitHSRP is first enabled
LearnWaiting to learn virtual IP
ListenRouter knows virtual IP but is not in active or standby state, waiting for message from active or standby routers
SpeakRouter is now sending hello messages and participating in router election
StandbyRouter is a candidate to become active router, continues sending hello's
ActiveActively forwarding packets sent to the virtual IP
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HSRP Load Balancing

Question Answer
Is ghettoNo 'load balance' command. Use two HSRP groups and split hosts default gateway between them
SetupIn grp1 R1 would be active and R2 would be standby, in grp2 R1 would be standby and R2 would be active
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VRRP

Question Answer
VRRPVirtual Router Redundancy Protocol, open standard RFC 2338
MasterActive router
BackupStandby router
PreemptionEnabled by default
Multicast224.0.0.18
Virtual MAC0000.5e00.01XX where XX is group number in hex
PriorityHigher is better
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