VRRP (Virtual Router Redundancy Protocol) is very similar to HSRP (Hot Standby Routing Protocol) and can be used to create a virtual gateway. If you don’t know why we use virtual gateways then I suggest to read my Introduction to virtual gateways first. Also make sure you check the HSRP lesson first since many of the things I describe there also apply to VRRP.
VRRP is very similar to HSRP; if you understood HSRP you’ll have no trouble with VRRP which is a standard protocol defined by the IETF in RFC 3768. Configuration-wise it’s pretty much the same but there are a couple of differences.
Let’s start with an overview:
|Protocol||Cisco proprietary||IETF – RFC 3768|
|Number of groups||16 groups maximum||255 groups maximum|
|Active/Standby||1 active, 1 standby and multiple candidates.||1 active and several backups.|
|Virtual IP Address||Different from real IP addresses on interfaces||Can be the same as the real IP address on an interface.|
|Tracking||Interfaces or Objects||Objects|
|Timers||Hello timer 3 seconds, hold time 10 seconds.||Hello timer 1 second, hold time 3 seconds.|
|Authentication||Supported||Not supported in RFC 3768|
As you can see there are a number of differences between HSRP and VRRP. Nothing too fancy however. HSRP is a cisco proprietary protocol so you can only use it between Cisco devices.
Let’s see if we can configure it…
This is the topology that I will use:
SW1 and SW2 are multilayer switches and their interfaces are configured as routed ports. We will create a virtual gateway using VRRP on the interfaces facing SW3:
SW1(config)#interface fa0/17 SW1(config-if)#vrrp 1 ip 192.168.1.3 SW1(config-if)#vrrp 1 priority 150 SW1(config-if)#vrrp 1 authentication md5 key-string mykey
SW2(config-if)#interface fa0/19 SW2(config-if)#vrrp 1 ip 192.168.1.3 SW2(config-if)#vrrp 1 authentication md5 key-string mykey
Here’s an example how to configure VRRP. You can see the commands are pretty much the same but I didn’t type “standby” but vrrp. I have changed the priority on SW1 to 150 and I’ve enabled MD5 authentication on both switches.
SW1# %VRRP-6-STATECHANGE: Fa0/17 Grp 1 state Init -> Backup %VRRP-6-STATECHANGE: Fa0/17 Grp 1 state Backup -> Master
SW2# %VRRP-6-STATECHANGE: Fa0/19 Grp 1 state Init -> Backup %VRRP-6-STATECHANGE: Fa0/19 Grp 1 state Backup -> Master %VRRP-6-STATECHANGE: Fa0/19 Grp 1 state Master -> Backup
You will see these messages pop-up in your console. VRRP uses different terminology than HSRP. SW1 has the best priority and will become the master router. SW2 will become a backup router. Let’s see what else we have:
SW1#show vrrp FastEthernet0/17 - Group 1 State is Master Virtual IP address is 192.168.1.3 Secondary Virtual IP address is 192.168.1.4 Virtual MAC address is 0000.5e00.0101 Advertisement interval is 1.000 sec Preemption enabled Priority is 150 Authentication MD5, key-string "mykey" Master Router is 192.168.1.1 (local), priority is 150 Master Advertisement interval is 1.000 sec Master Down interval is 3.414 sec
SW2#show vrrp FastEthernet0/19 - Group 1 State is Backup Virtual IP address is 192.168.1.3 Virtual MAC address is 0000.5e00.0101 Advertisement interval is 1.000 sec Preemption enabled Priority is 100 Authentication MD5, key-string "mykey" Master Router is 192.168.1.1, priority is 150 Master Advertisement interval is 1.000 sec Master Down interval is 3.609 sec (expires in 3.065 sec)
Use show vrrp to verify your configuration. The output looks similar to HSRP; one of the differences is that VRRP uses another virtual MAC address: