CCNA Advance

Chapter 2Hot Standby Routing Protocol

Configuring Layer 3 Redundancy with HSRP

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Routing Issues: Using Default Gateways

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Routing Issues: Using Proxy ARP

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Identifying the Router Redundancy Process

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Identifying the Router Redundancy Process

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Describing HSRP

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The Active Router

The active router responds to ARP requests with the well-known MAC address ofthe virtual router.

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The Virtual Router MAC Address

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The Standby Router

The standby router listens for periodic hello messages on 224.0.0.2

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Active and Standby Router Interaction

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Describing HSRP States

An HSRP router can be in one of six different states: Initial Learn Listen Speak Standby Active

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HSRP State Transition

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HSRP Standby State

A router in the standby state: Is a candidate for active router Sends hello messages Knows the virtual router IP address

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HSRP Active State

A router in the active state: Assumes the active forwarding of packets for the virtual router Sends hello messages Knows the virtual router IP address

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HSRP Configuration Commands

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Configuring an HSRP Standby Interface

Enabling HSRP on a Cisco router interface automaticallydisables ICMP redirects.

Optimizing HSRP

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HSRP Optimization Options

These options can be configured to optimize HSRP: HSRP standby priority HSRP standby preempt Hello message timers HSRP interface tracking

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Configuring HSRP Standby Priority

The router with the highest priority in an HSRP groupbecomes the active router. The default priority is 100. In the case of a tie, the router with the highestconfigured IP address will become active.

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Configuring HSRP Standby Preempt

Preempt enables a router to resume the forwarding router role.

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Configuring the Hello Message Timer

The holdtime parameter value should be at least threetimes the value of the hellotime parameter.

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HSRP Interface Tracking

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HSRP Interface Tracking (Cont.)

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Configuring HSRP Tracking

Configures HSRP tracking

Example of HSRP tracking

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Tuning HSRP

- Configure hellotime and holdtime to millisecond values.- Configure preempt delay timer so that preempt occurs only after the distribution switch has fully rebooted and established full connectivityto the rest of the network.

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Multiple HSRP Groups

To load balance routers, assign them to multiple groups on the same subnet.

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Addressing HSRP GroupsAcross Trunk Links

To loadbalance routersand links: Per VLAN,configurethe HSRPactiverouter andthespanningtree root tobe thesamemultilayerswitch.

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About the HSRP Debug Command

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Debugging HSRP

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Debugging HSRP (Cont.)

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Summary

Router redundancy allows two or more routers to work as a group to maintain forwarding of IP packets. A single default gateway or proxy ARP does not provide the redundancy required in a campus network. HSRP provides router redundancy to end devices. HSRP operates to provide nonstop path redundancy for IP. An HSRP-enabled router will exist in a specific state or transition through a series ofstates. HSRP is configured using the standby command. HSRP is enabled per interface. Preempt, timers, and interface tracking are options that can beconfigured to optimizeHSRP.

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Summary

HSRP preempt can be tuned by adjusting timers that can thereby reduce failover time. To facilitate load sharing, a single interface on a router can be a member of multiple HSRP groups. Specific debug commands are used to view HSRP state changes. Debug can be used to discover the virtual IP address and the priority of the active and standby routers.

Question ?

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CCNA AdvanceConfiguring Layer 3 Redundancy with HSRPRouting Issues: Using Default GatewaysRouting Issues: Using Proxy ARPIdentifying the Router Redundancy ProcessIdentifying the Router Redundancy ProcessDescribing HSRPThe Active RouterThe Virtual Router MAC AddressThe Standby RouterActive and Standby Router InteractionDescribing HSRP StatesHSRP State TransitionHSRP Standby StateHSRP Active StateHSRP Configuration CommandsConfiguring an HSRP Standby InterfaceOptimizing HSRPHSRP Optimization OptionsConfiguring HSRP Standby PriorityConfiguring HSRP Standby PreemptConfiguring the Hello Message TimerHSRP Interface TrackingHSRP Interface Tracking (Cont.)Configuring HSRP TrackingTuning HSRPMultiple HSRP GroupsAddressing HSRP GroupsAcross Trunk LinksAbout the HSRP Debug CommandDebugging HSRPDebugging HSRP (Cont.)SummarySummaryQuestion ?