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High Availability Commands for CCNP BCMSN

Sample Chapter is provided courtesy of Cisco Press.
Date: Nov 30, 2007.

Chapter Information

Chapter Description

This chapter provides information on and commands for Hot Standby Routing Protocol, Virtual Router Redundancy Protocol, and Gateway Load Balancing Protocol.

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This chapter provides information and commands concerning the following topics:

Hot Standby Routing Protocol (HSRP)
- —Configuring HSRP
- —Verifying HSRP
- —HSRP optimization options
- —Debugging HSRP
Virtual Router Redundancy Protocol (VRRP)
- —Configuring VRRP
- —Verifying VRRP
- —Debugging VRRP
Gateway Load Balancing Protocol (GLBP)
- —Configuring GLBP
- —Verifying GLBP
- —Debugging GLBP

Hot Standby Routing Protocol

The Hot Standby Router Protocol (HSRP) provides network redundancy for IP networks, ensuring that user traffic immediately and transparently recovers from first-hop failures in network edge devices or access circuits.

Configuring HSRP

`Router(config)#``interface fastethernet 0/0`	Moves to interface configuration mode
`Router(config-if)#` `ip address` `172.16.0.10 255.255.255.0`	Assigns IP address and netmask
`Router(config-if)#` `standby 1 ip 172.16.0.1`	Activates HSRP group 1 on the interface and creates a virtual IP address of 172.16.0.1 for use in HSRP
	NOTE The group number can be from 0 to 255. The default is 0.
`Router(config-if)#` `standby 1 priority 120`	Assigns a priority value of 120 to standby group 1
	NOTE The priority value can be from 1 to 255. The default is 100. A higher priority will result in that router being elected the active router. If the priorities of all routers in the group are equal, the router with the highest IP address becomes the active router.

Verifying HSRP

`Router#` `show running-config`	Displays what is currently running on the router
`Router#` `show standby`	Displays HSRP information
`Router#` `show standby brief`	Displays a single-line output summary of each standby group
`Router#` `show standby 1`	Displays HSRP group 1 information
`Router#` `show standby fastethernet 0/0`	Displays HSRP information for the specified interface
`Router#` `show standby fastethernet 0/0 brief`	Displays a summary of HSRP for the specified interface
`Router#` `show standby fastethernet 0/0 1`	Displays HSRP group 1 information for the specified interface

HSRP Optimization Options

There are options available that make it possible to optimize HSRP operation in the campus network. The next three sections explain three of these options: standby preempt, message timers, and interface tracking.

Preempt

`Router(config)#` `interface fastethernet 0/0`	Moves to interface configuration mode
`Router(config-if)#` `standby 1 preempt`	This router will preempt, or take control of, the active router if the local priority is higher than the active router
`Router(config-if)#` `standby 1 preempt delay minimum 180`	Causes the local router to postpone taking over as the active router for 180 seconds since that router was last restarted
`Router(config-if)#` `standby 1 preempt delay reload`	Allows for preemption to occur only after a router reloads
`Router(config-if)#` `no standby 1 preempt delay reload`	Disables the preemption delay, but preemption itself is still enabled. Use the no standby x preempt command to eliminate preemption
	NOTE If the preempt argument is not configured, the local router assumes control as the active router only if the local router receives information indicating that there is no router currently in the active state.

HSRP Message Timers

`Router(config)#` `interface fastethernet 0/0`	Moves to interface config mode
`Router(config-if)#` `standby 1 timers 5 15`	Sets the hello timer to 5 seconds and sets the hold timer to 15 seconds
	NOTE The hold timer is normally set to be greater than or equal to 3 times the hello timer.
	NOTE The hello timer can be from 1 to 254; the default is 3. The hold timer can be from 1 to 255; the default is 10. The default unit of time is seconds.
`Router(config-if)#` `standby 1 timers msec 200 msec 600`	Sets the hello timer to 200 milliseconds and sets the hold timer to 600 milliseconds
	NOTE If the msec argument is used, the timers can be an integer from 15 to 999.

Interface Tracking

`Router(config)#` `interface fastethernet 0/0`	Moves to interface configuration mode
`Router(config-if)#` `standby 1 track serial 0/0 25`	HSRP will track the availability of interface serial 0/0. If serial 0/0 goes down, the priority of the router in group 1 will be decremented by 25.
	NOTE The default value of the track argument is 10.
	TIP The track argument does not assign a new priority if the tracked interface goes down. The track argument assigns a value that the priority will be decreased if the tracked interface goes down. Therefore, if you are tracking serial 0/0 with a track value of 25—standby 1 track serial 0/0 25—and serial 0/0 goes down, the priority will be decreased by 25; assuming a default priority of 100, the new priority will now be 75.

Debugging HSRP

`Router#` `debug standby`	Displays all HSRP debugging information, including state changes and transmission/reception of HSRP packets
`Router#` `debug standby errors`	Displays HSRP error messages
`Router#` `debug standby events`	Displays HSRP event messages
`Router#` `debug standby events terse`	Displays all HSRP events except for hellos and advertisements
`Router#` `debug standby events track`	Displays all HSRP tracking events
`Router#` `debug standby packets`	Displays HSRP packet messages
`Router#` `debug standby terse`	Displays all HSRP errors, events, and packets, except for hellos and advertisements

2. Virtual Router Redundancy Protocol | Next Section

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