to the route processor.

∙Learn state—The route processor transitions to this state and remains in this state until it receives a hello message from the current active router. The hello message allows the route processor to learn the virtual IP address of the current virtual router.

∙Listen state—In this state, the route processor has learned the IP address of the virtual router and is listening for more updated information through hello messages. In this state, the route processor is neither active nor standing by. Listen is basically a transitional state from the Learn state to the Speak state.

∙Speak state—In this state, the route processor begins to forward its own periodic hello messages and to notify the other route processors that it is an active participant in the voting process to become an active or standby route processor. From here, it will forward to either the Active state or the Standby state.

∙Standby state—In HSRP, there must be at least one standby route processor. If more than one exists, the route processors become what are known as standby candidate route processors. The route processor with the highest standby priority will enter the Active state in the event of a failure.

∙Active state—The route processor in the Active state acts as the default gateway for the IP address assigned to the virtual router. It forwards any packets received for the virtual IP address or MAC address sent from any of the HSRP group’s host interfaces. It also continues to send hello messages to the other route processors to verify that it holds this function.

HSRP Configuration

You can configure more than one HSRP group on a Route Switch Feature Card (RSFC) VLAN interface to provide a transparent route processor backup per network. Every VLAN interface within an HSRP group shares a virtual IP and MAC address. By configuring the end users’ interfaces to use an HSRP virtual IP address as a default gateway, no interruption will occur in Layer 3 routing to the end users in the event of a failure of any route processor.

You can configure HSRP on a number of different types of Cisco route processors, including routers. You can configure multiple route processors on the same switch with interfaces for the same HSRP group. You can also configure multiple groups with multiple interfaces on the same route processor.

Disabling ICMP Redirects

It is important to disable all protocols that enable the host interfaces to discover the real MAC address of an HSRP standby group route processor interface. When enabling HSRP, ICMP redirects are automatically disabled. When you use the show running−configuration command under each VLAN interface configured for HSRP, a line will appear stating no ip redirects. This line indicates that ICMP redirects have been disabled. To re−enable an HSRP interface, enter Interface Configuration mode and use the command no standby, followed by the group number.

HSRP Interface Tracking

Interface tracking enables a standby group route processor to automatically adjust the priority levels based on the availability of the route processor. If a tracked interface becomes unavailable, the HSRP priority of the route processor is automatically decreased. When a route processor with HSRP tracking fails, it reduces the likelihood that a route processor with an unavailable interface will remain the active route processor for the

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standby group.

If a route processor fails, it automatically decrements its priority on that interface and stops transmitting hello messages out the interface. The standby route processor assumes the active router role when no hello messages are detected for the specified holdtime period.

Opening a Session on an Internal Route Processor

To configure HSRP on an internal route processor such as an RSFC or RSM, you must start a session using the session command. To start a session on the RSM located in slot 3, use the following command from Privileged mode on the switch Internetwork Operating System (IOS):

HSN_5K>(enable) session 3

Trying Router−3…

Connected to Router−3

HSN_5KRSM>

Entering Configuration Mode on an RSM

Once you have started a configuration session, you need to enter Configuration mode for the VLAN interface that needs to be identified. To configure the interface for VLAN 3, use the following commands:

HSN_5KRSM>enable

HSN_5KRSM#configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

HSN_5KRSM(config)#interface vlan 3

HSN_5KRSM(config−if)#

Enabling HSRP and Assigning an IP Address to a Standby Group

To enable HSRP and specify the virtual IP address, use the following command:

standby <group number> ip <virtual IP address>

For example, to make the group number 3 and the virtual IP address 63.78.39.254 you would enter the following:

standby 3 ip 63.78.39.254

Tip If you do not specify a group number, then group 0 is used by default. The IP address is the virtual IP address of the default gateway that you would assign manually or by DHCP to the end stations operating in this VLAN.

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Assigning an HSRP Interface Priority

You should increase the priority of the interface in the HSRP group that you would like to be active by default. Always remember that the interface with the highest priority becomes the active route processor for the HSRP group. To specify the priority for the HSRP interface, using the following command:

standby <standby group number> priority <priority>

In the following example, 3 refers to the HSRP standby group number corresponding to the VLAN interface number. The number 160 is the new priority for the HSRP group.

standby 3 priority 160

Note If no priority is configured, the interface priority defaults to 100.

Assigning a Preempt Delay to a Standby Group

You can assign the standby group a preempt delay. Doing so allows the interface to preempt the current active HSRP interface and become active if the interface priority is higher than the priority of the current active interface. The syntax for this command is:

standby <standby group> preempt <preempt delay>

To set the standby group 3 to a preempt delay of 10, use the following command:

standby 3 preempt 10

Removing a Preempt Delay from a Standby Group

To remove the route processor from preempt status, use the following syntax:

no standby <group number> preempt

To remove the preempt status for group number 3, enter the following:

no standby 3 preempt

Setting the HSRP Hello and Hold Timers

The default values for the HSRP timers are 3 seconds for the hello timer and 10 seconds for the hold timer. All the interfaces in the HSRP group should use the same timer values on all member route processors in the group. To set the hello timer and hold timer, use the following:

standby <HSRP group> timers <hello timer> <hold timer>

To set the hello timer to 5 seconds and the hold timer to 15 seconds for HSRP group 3, use the following command:

standby 3 timers 5 15

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Removing the HSRP Hello and Hold Timers

To remove the manual timer settings and return the settings to the default values for HSRP group 3, use the following command:

no standby 3 timers

Configuring a Clear−Text Password for HSRP Authentication

You can specify a clear−text password for the HSRP authentication string for the interface. All interfaces in the HSRP group use the same authentication string. The syntax is as follow:

standby <HSRP group> authentication <password>

To set the password book1 for HSRP group 3, use the following command:

standby 3 authentication book1

Configuring Two RSFC Interfaces as One HSRP Group

Now that you have learned the commands, let’s look at an example. This project shows how to configure two RSFC interfaces as part of HSRP group 200 using all the required and optional commands I’ve discussed. Notice that on both route processors, the same virtual IP address is used for both groups.

Here is the configuration of the first RSFC for the HSRP standby group 200:

The following is the configuration of the second RSFC. The priority setting here is lower than that of the first RSFC; thus the first RSFC is the active route processor (default gateway), and this RSFC is the standby route processor for the group:

HSN_KRSFC2#configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

HSN_5KRSFC2(config)#interface vlan200

HSN_5KRSFC2(config−if)#standby 200 ip 68.187.1.1

HSN_5KRSFC2(config−if)#standby 200 priority 100

HSN_5KRSFC2(config−if)#standby 200 preempt

HSN_5KRSFC2(config−if)#standby 200 timers 5 15

HSN_5KRSFC2(config−if)#standby 200 authentication password

HSN_5KRSFC2(config−if)#^Z

HSN_5KRSFC#

Here’s what happened:

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