VRRP or Virtual Router Redundancy Protocol is the open standard version of Ciscoâ€™s HSRP. It is also used to provide redundancy of a gateway by using multiple routers, but since itâ€™s an open standard then it can be implemented using routers from vendors other than Cisco. Most of VRRP logic are very similar to HSRP, and the way to Configure VRRP in Cisco IOS Router itself is almost the same.
Configure VRRP in Cisco IOS Router
In VRRP, the active router is called the master, and the standby router is called backup. This example will show how the VRRP configuration in Cisco CLI looks like, using the topology as specified below:
Configuration on R1 (master)
R1(config)#interface f0/0 R1(config-if)#ip address 10.1.1.1 255.255.255.0 R1(config-if)#no shutdown R1(config-if)#vrrp 123 ip 10.1.1.100 R1(config-if)#vrrp 123 preempt
Configuration on R2 (backup)
R2(config)#interface f0/0 R2(config-if)#ip address 10.1.1.2 255.255.255.0 R2(config-if)#no shutdown R2(config-if)#vrrp 123 ip 10.1.1.100 R2(config-if)#vrpp 123 priority 90
Similar to HSRP example in the previous article, weâ€™re using VRRP group number 123 and virtual IP is 10.1.1.100. And just like before, R2 has given lower priority (default VRRP priority is 100) so it becomes the backup, and will be the master if failure happens on R1. We also enable preemption on R1 so it will reclaim its role as the master when it is restored from a failure.
To verify VRRP status on each router we can use command show vrrp brief. The output is very straightforward, if you can understand how to read HSRP status, then you should have no problem understanding VRRP status. Everything is pretty much the same.
VRRP status on R1
R1#show vrrp brief Interface Grp Pri Time Own Pre State Master addr Group addr Fa0/0 123 100 3609 Y Master 10.1.1.1 10.1.1.100
VRRP status on R2
R2#show vrrp brief Interface Grp Pri Time Own Pre State Master addr Group addr Fa0/0 123 90 3648 Y Backup 10.1.1.1 10.1.1.100
Working in Mixed-Vendor Environment
VRRP is very useful in a mixed-vendor environment. We can configure VRRP in Cisco router to work with routers from other vendor in providing gateway redundancy. When we do, it is important to use the same timer values in all VRRP routers. Otherwise, they will not talk to each other and set themselves as the master, causing conflict in the network.
The timer that we refer here is the advertisement packet interval. By default, VRRP master sends a packet advertisement to its backup, indicating that it is still alive. Default interval on Cisco router is 1 second.
When using Cisco router as the master, we can modify the interval by adding command vrrp <group_number> timers advertise <interval> to specify interval in seconds, or use command vrrp <group_number> timers advertise msec <interval> to specify interval in milliseconds. For example:
Specifying interval to 2 seconds
R1(config-if)#vrrp 123 timers advertise 2
Specifying interval to 2000 milliseconds (equivalent to 2 seconds)
R1(config-if)#vrrp 123 timers advertise msec 2000
Both configurations above gives the same result on master router. However, if the Cisco router is a backup, we can simply add the configuration as shown below:
R2(config-if)#vrrp 123 timers learn
This will make the backup router to adapt with masterâ€™s advertisement interval. And that is how we configure VRRP in Cisco IOS Router.
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