HSRP

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Hot Standby Router Protocol

Virtual IP & MAC
MAC - 0000.0C07.ACxx (xx is hex for HSRP group)
3 second hello interval
10 second dead interval

Basic Configuration

config-if# standby 10 ip 172.16.1.1
config-if# standby priority 0...255 (100 is default)

Preempt

config-if# standby 10 preempt (reclaim position if you have higher priority then the current primary router)

Interface Tracking

config-if# standby 10 track s0/0 60 (lower priority by 60 if s0/0 goes down)
config# track 23 interface serial0/0.1 line-protocol
config-if# standby 1 track 23 decrement 60 

Authentication

config-if# standby 10 authentication WORD

Timers

config-if# standby 10 timers 1 4 (help and dead; dead = help x 3 + 1)

VVRP

000.5E00.01xx
IOS tracking feature, instead of own
preemption by default
Master = Active

GLBP

load-balancing features
gateway-redundancy features
0007.B400.xxyy (xx GLBP group number; yy is router number)
GLBP replies to ARPs with different MAC addresses for the different router
1024 GLBP groups per physical interface and 4 routers per group

View/Debug Commands

show standby
debug standby