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Example: Configuring VRRP for Load Sharing

Requirements

• Two QFX3500 switches
• Junos OS Release 11.3 or later
• Static routing or a dynamic routing protocol enabled on both switches.

Overview and Topology

This example uses two VRRP groups, each of which has its own virtual IP address. Devices on the LAN use one of these virtual IP addresses as their default gateway. If one of the switches fails, the other switch takes over for it. In the topology shown in Figure 1, for example, Switch A is the master for VRRP group 100. If Switch A fails, Switch B takes over and forwards traffic that the end devices send to the default gateway address 10.1.1.1.

Figure 1: VRRP Load-Sharing Configuration

This example shows a simple configuration to illustrate the basic steps for configuring two switches running VRRP to back each other up.Table 1 lists VRRP settings for each switch.

In addition to configuring the two switches as shown, you must configure your end devices so that some of them use one of the virtual IP addresses as their default gateway and the remaining end devices use the other virtual IP address as their default gateway.

Note that if a failover occurs, the remaining switch might be unable to handle all of the traffic, depending on the demand.

Configuring VRRP on Both Switches

CLI Quick Configuration

Enter the following on Switch A:

Enter the following on Switch B:

Step-by-Step Procedure

1. Create VRRP group 100 on Switch A and configure the virtual IP address for the group:
   [edit]
user@switch# set interfaces xe-0/0/0 unit 0 family inet address 10.1.1.252/24 vrrp-group 100 virtual-address 10.1.1.1
2. Assign the VRRP priority for this interface in this group:
   [edit]
user@switch# set interfaces xe-0/0/0 unit 0 family inet address 10.1.1.251/24 vrrp-group 100 priority 250
3. Create VRRP group 200 on Switch A and configure the virtual IP address for the group:
   [edit]
user@switch# set interfaces xe-0/0/0 unit 0 family inet address 10.1.1.251/24 vrrp-group 200 virtual-address 10.1.1.2
4. Assign the VRRP priority for this interface in this group:
   [edit]
user@switch# set interfaces xe-0/0/0 unit 0 family inet address 10.1.1.251/24 vrrp-group 100 priority 200

Step-by-Step Procedure

1. Create VRRP group 100 on Switch B and configure the virtual IP address for the group:
   [edit]
user@switch# set interfaces xe-0/0/0 unit 0 family inet address 10.1.1.252/24 vrrp-group 100 virtual-address 10.1.1.1
2. Assign the VRRP priority for this interface in this group:
   [edit]
user@switch# set interfaces xe-0/0/0 unit 0 family inet address 10.1.1.252/24 vrrp-group 100 priority 200

   Switch A remains the master for group 100 because it has the highest priority for this group.

3. Create VRRP group 200 on Switch A and configure the virtual IP address for the group:
   [edit]
user@switch# set interfaces xe-0/0/0 unit 0 family inet address 10.1.1.252/24 vrrp-group 200 virtual-address 10.1.1.2
4. Assign the VRRP priority for this interface in this group:
   [edit]
user@switch# set interfaces xe-0/0/0 unit 0 family inet address 10.1.1.251/24 vrrp-group 100 priority 250

   Switch B becomes the master for group 200 because it has the highest priority for this group.

Results

Display the results of the configuration on Switch A:

Display the results of the configuration on Switch B:

Verification

• Verifying that VRRP is Working on Switch A
• Verifying that VRRP is Working on Switch B

Verifying that VRRP is Working on Switch A

Purpose

Verify that VRRP is active on Switch A and that the master and backup roles are correct.

Action

Use the following command to verify that VRRP is active on Switch A and that the switch is master for group 100 and backup for group 200.

Interface        	State           Group 	  VR state      Timer               Type 	Address
xe-0/0/0.0     	up               100 	   master      A .0327		lcl  	10.1.1.251
                                                        			vip  	10.1.1.1
xe-0/0/0.0     	up               200 	   backup      A .0327		lcl  	10.1.1.251
                                                        			vip  	10.1.1.2

Meaning

The show vrrp command displays fundamental information about the VRRP configuration. This output shows that both VRRP groups are active and that this switch has assumed the correct master and backup roles. The lcl address is the physical address of the interface and the vip address is the virtual address shared by both switches. The Timer value (A .0327) indicates the remaining time (in seconds) in which this switch expects to receive a VRRP advertisement from the other switch. If an advertisement for group 200 does not arrive before the timer expires, Switch A asserts itself as the master for this group.

Verifying that VRRP is Working on Switch B

Purpose

Verify that VRRP is active on Switch B and that the master and backup roles are correct.

Action

Use the following command to verify that VRRP is active on Switch B and that the switch is backup for group 100 and master for group 200.

Interface        	State           Group 	  VR state      Timer               Type 	Address
xe-0/0/0.0     	up               100 	   backup      A .0327		lcl  	10.1.1.252
                                                        			vip  	10.1.1.1
xe-0/0/0.0     	up               200 	   master      A .0327		lcl  	10.1.1.252
                                                        			vip  	10.1.1.2

Meaning

The show vrrp command displays fundamental information about the VRRP configuration. This output shows that both VRRP groups are active and that this switch has assumed the correct master and backup roles. The lcl address is the physical address of the interface and the vip address is the virtual address shared by both switches. The Timer value (A .0327) indicates the remaining time (in seconds) in which this switch expects to receive a VRRP advertisement from the other switch. If an advertisement for group 100 does not arrive before the timer expires, Switch B asserts itself as the master for this group.