First Hop Redundancy Protocols Configuration Guide, Cisco IOS Release 15M&T - FHRP - HSRP Multiple Group Optimization [Cisco IOS 15.5M&T] (2024)

Perform this task to configure multiple HSRP groups for load balancing.

Multiple HSRP groups enable redundancy and load-sharing within networks and allow redundant devices to be more fully utilized. A device actively forwarding traffic for one HSRP group can be in standby or in the listen state for another group.

If two devices are used, then Device A would be configured as active for group 1 and standby for group 2. Device B would be standby for group 1 and active for group 2. Fifty percent of the hosts on the LAN would be configured with the virtual IP address of group 1 and the remaining hosts would be configured with the virtual IP address of group 2. See the Example: Multiple HSRP for Load Balancing section for a diagram and configuration example.

Perform this task to configure multiple HSRP client groups.

The standby follow command configures an HSRP group to become a slave of another HSRP group.

HSRP client groups follow the master HSRP with a slight, random delay so that all client groups do not change at the same time.

Use the standby mac-refresh seconds command to directly change the HSRP client group refresh interval. The default interval is 10 seconds and can be configured to as much as 255 seconds.

Note

Client or slave groups must be on the same physical interface as the master group. A client group takes its state from the group it is following. Therefore, the client group does not use its timer, priority, or preemption settings. A warning is displayed if these settings are configured on a client group: Device(config-if)# standby 1 priority 110%Warning: This setting has no effect while following another group.Device(config-if)# standby 1 timers 5 15 % Warning: This setting has no effect while following another group.Device(config-if)# standby 1 preempt delay minimum 300 % Warning: This setting has no effect while following another group.

Configure the HSRP master group using the steps in the Configuring Multiple HSRP Groups for Load Balancing section.

You can use HSRP or multiple HSRP groups when you configure load sharing. In the figure below, half of the clients are configured for Router A, and half of the clients are configured for Router B. Together, the configuration for Routers A and B establish two Hot Standby groups. For group 1, Router A is the default active router because it has the assigned highest priority, and Router B is the standby router. For group 2, Router B is the default active router because it has the assigned highest priority, and Router A is the standby router. During normal operation, the two routers share the IP traffic load. When either router becomes unavailable, the other router becomes active and assumes the packet-transfer functions of the router that is unavailable. The standby preempt interface configuration command is necessary so that if a router goes down and then comes back up, preemption occurs and restores load sharing.

Figure 1. HSRP Load Sharing Example

The following example shows Router A configured as the active router for group 1 with a priority of 110 and Router B configured as the active router for group 2 with a priority of 110. The default priority level is 100. Group 1 uses a virtual IP address of 10.0.0.3 and Group 2 uses a virtual IP address of 10.0.0.4.

Router A Configuration

Router(config)# hostname RouterA!Router(config)# interface GigabitEthernet 0/0/0Router(config-if)# ip address 10.0.0.1 255.255.255.0Router(config-if)# standby 1 priority 110Router(config-if)# standby 1 preemptRouter(config-if)# standby 1 ip 10.0.0.3Router(config-if)# standby 2 preemptRouter(config-if)# standby 2 ip 10.0.0.4

Router B Configuration

Router(config)# hostname RouterB!Router(config)# interface GigabitEthernet 0/0/0Router(config-if)# ip address 10.0.0.2 255.255.255.0Router(config-if)# standby 1 preemptRouter(config-if)# standby 1 ip 10.0.0.3Router(config-if)# standby 2 priority 110Router(config-if)# standby 2 preemptRouter(config-if)# standby 2 ip 10.0.0.4

The following example shows how to configure an HSRP client and master group:

Device(config)# interface GigabitEthernet 0/0/0Device(config-if)# no shutdownDevice(config-if)# standby mac-refresh 30 ! Client Hello message interval!Device(config)# interface GigabitEthernet 0/0/1Device(config-if)# no shutdownDevice(config-if)# ip vrf forwarding VRF2Device(config-if)# ip address 10.0.0.100 255.255.0.0Device(config-if)# standby 1 ip 10.0.0.254Device(config-if)# standby 1 priority 110Device(config-if)# standby 1 preemptDevice(config-if)# standby 1 name HSRP1 !Server group!Device(config)# interface GigabitEthernet 0/0/2Device(config-if)# no shutdownDevice(config-if)# ip vrf forwarding VRF3Device(config-if)# ip address 10.0.0.100 255.255.0.0Device(config-if)# standby 2 ip 10.0.0.254Device(config-if)# standby 2 follow HSRP1 ! Client group!Device(config)# interface GigabitEthernet 0/0/3Device(config-if)# no shutdownDevice(config-if)# ip vrf forwarding VRF4Device(config-if)# ip address 10.0.0.100 255.255.0.0Device(config-if)# standby 2 ip 10.0.0.254Device(config-if)# standby 2 follow HSRP1 ! Client group