Let’s talk about too routers A and B that use the HSRP protocole against tolerance fault and attack.

The router A use the IP address 192.168.0.2 with a mask 255.255.255.0
The router B use the IP address 192.168.0.3 with a mask 255.255.255.0
So, the virtual IP address is 192.168.0.1 and is set as default gateway as:
Router A
interface Ethernet 0/0
ip address 192.168.0.2 255.255.255.0
standby 10 priority 100 preempt
standby 10 ip 192.168.0.1
Router B
interface Ethernet 0/0
ip address 192.168.0.3 255.255.255.0
standby 10 priority 80
standby 10 ip 192.168.0.1