Along with configuring priority, configure preempt to allow a router to take
over if the active router has lower priority, as shown in the following
commands. This helps lead to a predictable data path through the network.
The second command shown delays preemption until the router or switch
has fully booted, and the routing protocol has converged. Time how long it
takes to boot and add 50 percent to get the delay value in seconds:
Router(config-if)#standby 39 preempt
Router(config-if)#standby 39 preempt delay minimum 90
Speed convergence by changing the hello and hold timers. The following
sets the hello interval to 2 seconds and the hold time to 7 seconds. They can
be set between 1–255 seconds (the default hello is 3 seconds and hold time
is 10 seconds):
Router(config-if)#standby 39 timers 2 7
Tracking an interface can trigger an election if the active router is still up,
but a critical interface (such as the one to the Internet) is down. In the
following, if serial 1/0/0 is down, the router’s HSRP priority is decremented
by 100:
Router(config-if)#standby 39 track s1/0/00 100
Note
The standby router must be configured with the preempt command for it to take control.
Multiple HSRP standby groups can be configured, and the same router can
be active for some groups and standby for others by adjusting priorities. You
can have a maximum of 255 groups. When using Layer 3 switches, configure
the same switch as the primary HSRP router and the Spanning Tree root.
To view the HSRP status, use the show standby interface interface
command, or show standby brief. To monitor HSRP activity, use the debug
standby command.