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CCNA Routing and Switching Practice and Study Guide: LAN Redundancy

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: May 15, 2014.

Chapter Description

To help you prepare for the ICND2 200-101 Certification Exam, this chapter investigates how Spanning Tree Protocol (STP) logically blocks physical loops in the network and how STP has evolved into a robust protocol that rapidly calculates which ports should be blocked in a VLAN-based network.

First Hop Redundancy Protocols

Up to this point, we’ve been reviewing STP and how to manipulate the election of root bridges and load balance across redundant links. In addition to Layer 1 and Layer 2 redundancy, a high-availability network might also implement Layer 3 redundancy by sharing the default gateway responsibility across multiple devices. Through the use of a virtual IP address, two Layer 3 devices can share the default gateway responsibility. The section reviews First Hop Redundancy Protocols (FHRPs) that provide Layer 3 redundancy.

Identify FHRP Terminology

Match the definition on the left with the terms on the right. This is a one-to-one matching exercise.



  • _______ The ability to dynamically recover from the failure of a device acting as the default gateway
  • _______ Two or more routers sharing a single MAC and IP address
  • _______ A device that is part of a virtual router group assigned to the role of default gateway
  • _______ Provides the mechanism for determining which router should take the active role in forwarding traffic
  • _______ A device that routes traffic destined to network segments beyond the source network segment
  • _______ A device that is part of a virtual router group assigned the role of alternate default gateway
  • _______ A Layer 3 address assigned to a protocol that shares the single address among multiple devices
  • _______ The Layer 2 address returned by ARP for an FHRP gateway
  • a. Default gateway
  • b. First-hop redundancy
  • c. Forwarding router
  • d. Redundancy rrotocol
  • e. Standby router
  • f. Virtual IP address
  • g. Virtual MAC address
  • h. Virtual router

Identify the Type of FHRP

In Table 2-7, indicate whether the characteristic describes HSRP, VRRP, or GLBP.

Table 2-7 FHRP Characteristics

FHRP Characteristic




Used in a group of routers for selecting an active device and a standby device.

A nonproprietary election protocol that allows several routers on a multi-access link to use the same virtual IPv4 address.

Cisco-proprietary FHRP protocol designed to allow for transparent failover of a first-hop IPv4 devices.

Cisco-proprietary FHRP protocol that protects data traffic from a failed router or circuit while also allowing load sharing between a group of redundant routers.

One router is elected as the virtual router master, with the other routers acting as backups in case the virtual router master fails.

HSRP and GLBP Configuration and Verification

Refer to the topology in Figure 2-6. R2 has been configured for HSRP group 20, priority 120, IP address, and virtual IP address

Figure 2-6

Figure 2-6 HSRP and GLBP Configuration Topology

Example 2-1 shows the HSRP configuration for R2.

Example 2-1 R2 HSRP Configuration

R2# show run interface g0/1
<output omitted>
interface GigabitEthernet0/1
 ip address
 standby 20 ip
 standby 20 priority 120
<output omitted>

Using the information in Example 2-1, document the commands to configure R1 as the HSRP active router in group 20 using a priority of 210.



What command would generate the following output to verify the HSRP configuration?

                     P indicates configured to preempt.
Interface   Grp  Pri P State   Active          Standby         Virtual IP
Gi0/1       20   210   Active  local 

Now assume that all HSRP configurations have been removed. R2 has been configured for GLBP group 20, priority 120, IP address, and virtual IP address

Example 2-2 shows the GLBP configuration for R2.

Example 2-2 R2 GLBP Configuration

R2# show run interface g0/1
<output omitted>
interface GigabitEthernet0/1
 ip address
 glbp 20 ip
 glbp 20 priority 120
<output omitted>

Using the information in Example 2-2, document the commands to configure R1 to be in GLBP group 20 using a priority of 210.



What command would generate the following output to verify the GLBP configuration?

GigabitEthernet0/0 - Group 20
  State is Active
    1 state change, last state change 00:03:05
  Virtual IP address is
  Hello time 3 sec, hold time 10 sec
    Next hello sent in 1.792 secs
  Redirect time 600 sec, forwarder timeout 14400 sec
  Preemption disabled
  Active is local
  Standby is, priority 120 (expires in 9.024 sec)
  Priority 210 (configured)
  Weighting 100 (default 100), thresholds: lower 1, upper 100
  Load balancing: round-robin
  Group members:
    0006.f671.db58 ( local
    0006.f671.eb38 (
  There are 2 forwarders (1 active)
  Forwarder 1
    State is Active
      1 state change, last state change 00:02:53
    MAC address is 0007.b400.0a01 (default)
    Owner ID is 0006.f671.db58
    Redirection enabled
    Preemption enabled, min delay 30 sec
    Active is local, weighting 100
  Forwarder 2
    State is Listen
    MAC address is 0007.b400.0a02 (learnt)
    Owner ID is 0006.f671.eb38
    Redirection enabled, 599.040 sec remaining (maximum 600 sec)
    Time to live: 14399.040 sec (maximum 14400 sec)
    Preemption enabled, min delay 30 sec
    Active is (primary), weighting 100 (expires in 9.312 sec)

Lab - Configuring HSRP and GLBP (SN


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