GLBP: Gateway Load Balancing Protocol

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Questions and Answers

How does GLBP differ from HSRP and VRRP in handling traffic for a virtual IP address?

  • GLBP forwards all traffic to a single active router, whereas HSRP and VRRP distribute traffic based on VLAN.
  • GLBP can load balance traffic among multiple routers in a group, while HSRP and VRRP primarily provide redundancy. (correct)
  • GLBP only supports one active gateway, similar to HSRP, but unlike VRRP.
  • GLBP exclusively uses physical MAC addresses, unlike HSRP and VRRP.

What is the maximum number of primary active virtual forwarders (AVFs) that a GLBP group can support?

  • Unlimited, depending on the network configuration.
  • 2
  • 4 (correct)
  • 1

What role does the Active Virtual Gateway (AVG) play in a GLBP group?

  • It assigns virtual MAC addresses to the primary AVFs and responds to ARP requests. (correct)
  • It acts as a backup in case the Active Virtual Forwarder fails.
  • It forwards all traffic to the physical gateway.
  • It monitors the health of other routers but does not forward traffic.

When the AVG receives an ARP request destined for the GLBP group's virtual IP address, how does it respond to facilitate load balancing?

<p>It responds with a different virtual MAC address for each primary AVF, including its own. (D)</p> Signup and view all the answers

In a GLBP group, what happens if the AVG fails?

<p>The Standby Virtual Gateway (SVG) with the next highest priority takes over as the AVG. (B)</p> Signup and view all the answers

If an Active Virtual Forwarder (AVF) in a GLBP group fails, what action does the AVG take?

<p>The AVG assigns the role of the failed AVF to another router within the GLBP group. (C)</p> Signup and view all the answers

Which term describes the routers in a GLBP group that are neither the AVG nor primary AVFs?

<p>Secondary Virtual Forwarders (SVFs) (C)</p> Signup and view all the answers

For a network using GLBP, which address do devices use as their default gateway?

<p>The virtual IP address configured for the GLBP group. (A)</p> Signup and view all the answers

Which protocol is used by the Active Virtual Gateway (AVG) to inform network devices of the virtual MAC addresses?

<p>ARP (Address Resolution Protocol) (C)</p> Signup and view all the answers

How does assigning different virtual MAC addresses to AVFs by the AVG improve network performance?

<p>It allows for traffic load balancing across multiple gateways, preventing bottlenecks. (A)</p> Signup and view all the answers

What is the primary benefit of using GLBP for router redundancy and load balancing?

<p>It increases network reliability while optimizing bandwidth usage through load distribution. (B)</p> Signup and view all the answers

In a GLBP setup, how many routers can actively forward traffic at the same time under normal operating conditions?

<p>Up to four Active Virtual Forwarders (AVFs) plus the AVG. (C)</p> Signup and view all the answers

Which statement accurately describes the role transition when the current AVG fails in a GLBP group?

<p>The Standby Virtual Gateway (SVG) with the next highest priority becomes the new AVG. (A)</p> Signup and view all the answers

What is a key consideration when configuring priorities for routers in a GLBP group?

<p>The router intended as the primary AVG should be configured with the highest priority. (C)</p> Signup and view all the answers

How does GLBP ensure minimal disruption during a failover event?

<p>By having the SVG immediately assume the AVG role and continue forwarding traffic using virtual MAC addresses. (C)</p> Signup and view all the answers

In a GLBP environment, what would happen if an AVF starts experiencing high CPU utilization?

<p>The AVG would automatically redistribute the AVF's assigned traffic to other available AVFs. (A)</p> Signup and view all the answers

Which of the following is a limitation of GLBP compared to other gateway redundancy protocols?

<p>It is a Cisco-proprietary protocol, limiting its adoption in heterogeneous network environments. (D)</p> Signup and view all the answers

How does GLBP improve network scalability compared to traditional FHRPs like HSRP?

<p>By allowing multiple gateways to actively forward traffic simultaneously, better utilizing network resources. (C)</p> Signup and view all the answers

What impact does GLBP have on the convergence time during a failover, compared to HSRP or VRRP?

<p>GLBP offers faster convergence times by immediately activating a standby gateway. (A)</p> Signup and view all the answers

How can you verify the operational status of GLBP on a Cisco router?

<p>By using the <code>show glbp</code> command to display GLBP group information and status. (D)</p> Signup and view all the answers

Flashcards

What is GLBP?

Cisco-proprietary protocol offering router redundancy and load balancing across multiple routers in a group.

What is the Active Virtual Gateway (AVG)?

One router in a GLBP group that assigns virtual MAC addresses to primary AVFs.

What are Active Virtual Forwarders (AVFs)?

Up to four routers in a GLBP group that forward traffic sent to the virtual IP address, each having a unique virtual MAC address.

What are Secondary Virtual Forwarders (SVFs)?

Routers in a GLBP group that are not currently AVFs but can take over if an AVF fails.

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What is the Standby Virtual Gateway (SVG)?

The router with the next highest priority that takes over the AVG's role if the current AVG fails.

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How does GLBP load balance traffic?

GLBP shares the traffic load amongst multiple routers, unlike HSRP and VRRP.

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How does the AVG facilitate load balancing?

The AVG responds to ARP requests with different virtual MAC addresses for each AVF.

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What event triggers the SVG to take over as the AVG?

If the AVG fails.

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What happens if an AVF fails?

The AVG assigns another router to be an AVF.

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Study Notes

  • GLBP is a Cisco protocol which provides router redundancy and load balancing
  • Routers in a GLBP group receive traffic sent to a virtual IP address configured for the group
  • GLBP can load balance traffic among every router, unlike HSRP and VRRP
  • Each GLBP group contains:
    • One active virtual gateway (AVG)
    • Up to four primary active virtual forwarders (AVFs)
    • Remaining routers become secondary virtual forwarders (SVFs)
  • The AVG assigns a virtual MAC address to the primary AVFs
  • When the AVG receives ARP requests sent to the virtual IP address, the AVG responds with a different virtual MAC address, including its own
  • Load balancing is achieved, because each of the primary AVFs can participate by forwarding a portion of the traffic sent to the virtual IP address
  • If the AVG fails, the AVF with the next highest priority (SVG) will take over for the AVG
  • If one of the AVFs fails, the AVG will assign another router the role of that AVF

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