Hot Standby Router Protocol – HSRP is cisco proprietary protocol for network redundancy. This protocol use active-standby method to provide redundancy in network.
Today most of the company have Internet connectivity. Biggest problem with their network is redundancy of network devices. Below is picture which describe default network topology:-
In Default network topology we have 1 Internet Gateway Router (IGR), 1 Firewall for Security in Transparent or routed mode and 1 L3 switch for local Network Distribution. In case of any device (IGR, Firewall or L3 Switch ) gets down whole network will be down until and unless you don’t replace or reconfigure it again.
With help of HSRP you can deploy below redundant topology:-
Both Router and Switches are using HSRP for redundancy of network for Firewall it will be different protocol.
How HSRP Works?
HSRP use active standby method to get redundancy of network. Each router have one unique IP and 1 shared IP. That shared IP will be active on only one device and that device will be active device and other will be standby, HSRP keeps monitoring other device for failover if active device goes down then standby device make itself active and start using shared IP as active IP.
Selection of Active router works on my rules.
By default first boot device become active
In case of more then 2 HSRP enabled devices, if Active goes down then highest IP become active.
We can manually define Active router by configuring priority of router with help of preempt.
HSRP can be configured on more then 2 device for more redundancy purpose. For this article I am using only 2 device.
Step 1:- First configure IP address on both devices (I am using 2 L3 switches for lab):-
S1(config-if)# ip address 192.168.1.2 255.255.255.0 S2
S2(config-if)# ip address 192.168.1.3 255.255.255.0
Step 2:- Configure HSRP
Configure IP address which will be available for Active Device, (On both devices)
S1(config-if)#standby ip 192.168.1.1
S2(config-if)#standby ip 192.168.1.1
That’s it for HSRP, your hsrp is running on both devices now.. To check use below command:-
In above result look for Virtual IP (192.168.1.1) is same on both devices, but is active on S2 and standby on S1.
To configure Priority of device we need to configure priority on devices and then ask device to check priority with help of preempt.
To make S1 as Active we need to configure its priority high.