HSRP

Hot Standby Router Protocol group configuration, preemption, and object tracking for gateway redundancy.

HSRP Configuration

HSRPv2 basic config — virtual IP shared between two routers; highest priority is active

configure terminal
interface GigabitEthernet0/0/0
 ip address 10.50.1.2 255.255.255.0
 standby version 2
 standby 1 ip 10.50.1.1
 standby 1 priority 110
 standby 1 preempt
end

Standby router (lower priority) — same group number and virtual IP

configure terminal
interface GigabitEthernet0/0/0
 ip address 10.50.1.3 255.255.255.0
 standby version 2
 standby 1 ip 10.50.1.1
 standby 1 priority 100
 standby 1 preempt
end

HSRPv2 vs HSRPv1

HSRPv2 — extended group range (0-4095), uses 224.0.0.102, millisecond timers, different virtual MAC format

! HSRPv1: group range 0-255, MAC 0000.0c07.acXX
! HSRPv2: group range 0-4095, MAC 0000.0c9f.fXXX
! Always use HSRPv2 — HSRPv1 is legacy

configure terminal
interface GigabitEthernet0/0/0
 standby version 2
end

HSRP Preempt

Preempt — allows higher priority router to take over active role; disabled by default

configure terminal
interface GigabitEthernet0/0/0
 standby 1 preempt
 standby 1 preempt delay minimum 30
end

HSRP Timers

Adjust hello and hold timers — default hello 3s, hold 10s; millisecond timers for fast failover

configure terminal
interface GigabitEthernet0/0/0
 standby 1 timers 1 3
end

! Millisecond timers — 200ms hello, 700ms hold
configure terminal
interface GigabitEthernet0/0/0
 standby 1 timers msec 200 msec 700
end

HSRP Interface Tracking

Track an upstream interface — decrement priority when tracked interface goes down; triggers preempt failover

configure terminal
track 1 interface GigabitEthernet0/0/1 line-protocol
!
interface GigabitEthernet0/0/0
 standby 1 track 1 decrement 20
end

Track an IP route — more flexible than interface tracking; monitors reachability

configure terminal
track 10 ip route 0.0.0.0/0 reachability
!
interface GigabitEthernet0/0/0
 standby 1 track 10 decrement 20
end

HSRP Verification

Show HSRP state — active/standby role, virtual IP, priority, preempt status, timers

show standby
show standby brief
show standby GigabitEthernet0/0/0

Key fields in show standby output

! State:     Active / Standby / Init / Learn / Speak
! Priority:  110 (configured) - 20 (decrement) = 90 (effective)
! Preempt:   enabled / disabled
! Virtual IP: 10.50.1.1
! Active:    local / 10.50.1.3

VRRP Configuration

VRRP — IETF standard (RFC 5798); master owns the virtual IP if it matches a real interface IP

configure terminal
interface GigabitEthernet0/0/0
 ip address 10.50.1.2 255.255.255.0
 vrrp 1 address-family ipv4
  address 10.50.1.1 primary
  priority 110
  preempt delay minimum 30
  track 1 decrement 20
 exit-vrrp
end

VRRP vs HSRP comparison

! VRRP: IETF standard, master/backup, multicast 224.0.0.18
!   - Master can own the virtual IP (no phantom IP needed)
!   - Preempt enabled by default
!   - Default priority 100, range 1-254
!
! HSRP: Cisco proprietary, active/standby, multicast 224.0.0.102
!   - Virtual IP is always phantom (not owned by any interface)
!   - Preempt disabled by default
!   - Default priority 100, range 0-255

GLBP Configuration

GLBP — Cisco proprietary; provides load balancing across multiple forwarders using single virtual IP

configure terminal
interface GigabitEthernet0/0/0
 ip address 10.50.1.2 255.255.255.0
 glbp 1 ip 10.50.1.1
 glbp 1 priority 110
 glbp 1 preempt
 glbp 1 load-balancing round-robin
end

GLBP roles — AVG (Active Virtual Gateway) assigns AVF (Active Virtual Forwarder) roles; each AVF has a unique virtual MAC

! AVG: Answers ARP for virtual IP, assigns virtual MACs to AVFs
! AVF: Each gateway forwards traffic for its assigned virtual MAC
! Load-balancing methods:
!   round-robin  — distributes MACs to hosts sequentially (default)
!   weighted     — proportional to configured weight
!   host-dependent — consistent MAC per host (based on source MAC)

GLBP with tracking

configure terminal
interface GigabitEthernet0/0/0
 glbp 1 weighting 110 lower 95 upper 105
 glbp 1 weighting track 1 decrement 20
end

GLBP verification

show glbp
show glbp brief

Verification Summary

Key show commands for FHRP troubleshooting

show standby
show standby brief
show vrrp
show vrrp brief
show glbp
show glbp brief
show track