VRRP, Virtual Router Redundancy Protocol

conf t
hostname R1
int e0/1
ip address 10.2.2.1 255.255.255.0
vrrp 100 ip 10.2.2.12
vrrp 100 priority 90
no shut


conf t
hostname R2
int e0/1
ip address 10.2.2.2 255.255.255.0
vrrp 100 ip 10.2.2.12

no shut
========================
!for verification

R1#show vrrp all
Ethernet0/1 - Group 100
State is Backup
Virtual IP address is 10.2.2.12
Virtual MAC address is 0000.5e00.0164
Advertisement interval is 1.000 sec
Preemption enabled
Priority is 90
Master Router is 10.2.2.2, priority is 100
Master Advertisement interval is 1.000 sec
Master Down interval is 3.648 sec (expires in 3.112 sec)
R1#

*Mar 1 00:33:13.967: %VRRP-6-STATECHANGE: Et0/1 Grp 100 state Backup -> Master
R1#show vrrp all
Ethernet0/1 - Group 100
State is Master
Virtual IP address is 10.2.2.12
Virtual MAC address is 0000.5e00.0164
Advertisement interval is 1.000 sec
Preemption enabled
Priority is 90
Master Router is 10.2.2.1 (local), priority is 90
Master Advertisement interval is 1.000 sec

Master Down interval is 3.648 sec

R2#show vrrp brief
Interface Grp Pri Time Own Pre State Master addr Group addr
Et0/1 100 100 3609 Y Master 10.2.2.2 10.2.2.12

R2#show vrrp interface ethernet 0/1
Ethernet0/1 - Group 100
State is Master
Virtual IP address is 10.2.2.12
Virtual MAC address is 0000.5e00.0164
Advertisement interval is 1.000 sec
Preemption enabled
Priority is 100
Master Router is 10.2.2.2 (local), priority is 100
Master Advertisement interval is 1.000 sec
Master Down interval is 3.609 sec

Notes:
redundancy protocols,

1. HSRP
2. VRRP
3. GLBP

all having the similar logic, using VIRTUAL INTERFACE. (10.2.2.12 in this case)

hence, the down-stream device able to configure ip default-gateway 10.2.2.12