23-6
Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-03
Chapter 23 Configuring HSRP
Configuring HSRP
Configuring HSRP Group Attributes
Although HSRP can run with no other configuration required, you can configure attributes for the HSRP
group, including authentication, priority, preemption and preemption delay, timers, or MAC address.
Configuring HSRP Priority
The standby priority, standby preempt, and standby track interface configuration commands are all
used to set characteristics for determining active and standby routers and behavior regarding when a new
active router takes over. When configuring priority, follow these guidelines:
•
Assigning priority helps select the active and standby routers. If preemption is enabled, the router
with the highest priority becomes the designated active router. If priorities are equal, the primary IP
addresses are compared, and the higher IP address has priority.
•
The highest number (1 to 255) represents the highest priority (most likely to become the active
router).
•
When setting the priority, preempt, or both, you must specify at least one keyword (priority,
preempt, or both).
•
The priority of the device can change dynamically if an interface is configured with the standby
track command and another interface on the router goes down.
•
The standby track interface configuration command ties the router hot standby priority to the
availability of its interfaces and is useful for tracking interfaces that are not configured for HSRP.
When a tracked interface fails, the hot standby priority on the device on which tracking has been
configured decreases by 10. If an interface is not tracked, its state changes do not affect the hot
standby priority of the configured device. For each interface configured for hot standby, you can
configure a separate list of interfaces to be tracked.
•
The standby track interface-priority interface configuration command specifies how much to
decrement the hot standby priority when a tracked interface goes down. When the interface comes
back up, the priority is incremented by the same amount.
•
When multiple tracked interfaces are down and interface-priority values have been configured, the
configured priority decrements are cumulative. If tracked interfaces that were not configured with
priority values fail, the default decrement is 10, and it is noncumulative.
•
When routing is first enabled for the interface, it does not have a complete routing table. If it is
configured to preempt, it becomes the active router, even though it is unable to provide adequate
routing services. To solve this problem, configure a delay time to allow the router to update its
routing table.
