Specifications

CHAPTER 6

First Hop Redundancy

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 (the default

value to decrement is 10):

Router(config-if)# standby 39 track s1/0/0 100

Another way to track an indirect connection is to use IP SLA (described in Chapter 5). With IP SLA tracking, HSRP can

failover to the standby router if any connection on the path to a remote location fails or exceeds link-quality thresholds.

The following sample configuration shows how to add tracking an IP SLA session number 5 to an existing HSRP inter-

face configuration.

Router(config)#ip sla 5

Router(config-ip-sla)# udp-jitter 172.17.1.2 16000

Router(config)#track 10 rtr 5

Router(config-if)# int fa 1/0/15

Router(config-if)# stand 2 track 10 decrement 50

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.

Virtual Router Redundancy Protocol

Virtual Router Redundancy Protocol (VRRP) is similar to HSRP, but it is an open standard (RFC 2338). Two or more

devices act as a virtual router. With VRRP, however, the IP address used can be either a virtual one or the actual IP

address of the primary router. VRRP is supported only on Cisco 4500 and 6500 series switches.

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CCNP SWITCH 642-813 Quick Reference by Denise Donohue

Note:

The standby router must

be configured with the

preempt command for it

to take control.