The purpose of this short tutorial is to show you how to configure a simple redundant HSRP link between two Cisco routers. For the purposes of the article the hardware used was two Cisco 7200 (12.4(23b)) routers.
Initial setup
I am starting from the point where I already have two working routers that can ping each other. R1 has an IP address of 192.168.1.252 and R2 has an IP address of 192.168.2.253. R1 can ping R2 and vice versa. These two routers connect to a switch, the switch also has a PC connected with IP address 192.168.1.1 and a gateway address of 192.168.1.254.
This is our base starting point, see diagram below.
The purpose of this exercise is to create the PC’s gateway address, 192.168.1.254, as a virtual address on the two routers, so if one router goes down, the other will take over the gateway address and the PC will not lose connectivity. We have setup a test 100.100.100.1 destination address for testing purposes. It is beyond the scope of this tutorial to explain how anything in the green circle on the diagram is configured.
Configuring the interfaces on R1 and R2
The interface f0/0 on R1 and R2 have an extremely simple initial configuration, on R1 we have -:
interface FastEthernet0/0 ip address 192.168.1.252 255.255.255.0 duplex full
And on R2 we have -:
interface FastEthernet0/0 ip address 192.168.1.253 255.255.255.0 duplex full
To get HSRP up and running only requires one simple command on each router, on R1 and R2 we need to add the following to get HSRP, in it’s most basic form, up and running -:
interface FastEthernet0/0 standby ip 192.168.1.254
That’s it, the routers are now configured for HSRP, wasn’t that easy?
Confirm HSRP is working correctly
We really should check to see what HSRP is doing and if it is working properly, so on R1 run the command sh standby f0/0 and examine the output.
FastEthernet0/0 - Group 0 State is Active 5 state changes, last state change 00:00:15 Virtual IP address is 192.168.1.254 Active virtual MAC address is 0000.0c07.ac00 Local virtual MAC address is 0000.0c07.ac00 (v1 default) Hello time 3 sec, hold time 10 sec Next hello sent in 0.000 secs Preemption disabled Active router is local Standby router is 192.168.1.253, priority 100 (expires in 8.648 sec) Priority 100 (default 100) IP redundancy name is "hsrp-Fa0/0-0" (default)
From the output we can see that the ‘Active Router’ is local (e.g. R1 itself) and the ‘Standby Router’ is 192.168.2.153 (R2). Now if we shut down interface F0/0 on R1, we can simulate what happens in the event of a link failure. So do that now and examine the output of the sh standby f0/0 on R2.
FastEthernet0/0 - Group 0 State is Active 5 state changes, last state change 00:00:24 Virtual IP address is 192.168.1.254 Active virtual MAC address is 0000.0c07.ac00 Local virtual MAC address is 0000.0c07.ac00 (v1 default) Hello time 3 sec, hold time 10 sec Next hello sent in 2.260 secs Preemption disabled Active router is local Standby router is unknown Priority 100 (default 100) IP redundancy name is "hsrp-Fa0/0-0" (default)
So we now see the R2 is reporting itself as the ‘Active Router’ and the ‘Standby Router’ is unknown, which makes sense as the interface on R1 is currently down. From the PC you would have noticed a few dropped pings while R2 took over the virtual IP address, but connectivity would have been restored rather quickly.
Congratulations, you now have a fully redundant router set-up for the default gateway on your network! Remember, this is only very basic HSRP functionality, a later tutorial will explore HSRP a little further and investigate some of the more advanced functions available.