Exploring Layer 3 Redundancy

Question 1

Are a group of protocols with similar functionality that enable a set of routers or Layer 3 switches to present an illusion of a “virtual” router.

Answer 1

First Hop Redundancy Protocols (FHRPs)

Question 2

Is assigned a virtual IP address and virtual MAC address, which is shared by two routers.

Answer 2

virtual router

Question 3

HSRP is an FHRP that Cisco designed to create a redundancy framework between network routers or Layer 3 switches to achieve default gateway failover capabilities. Only one router per subnet forwards traffic.

Answer 3

Hot Standby Router Protocol (HSRP)

Question 4

VRRP is an open FHRP standard that offers the ability to add more than two routers for additional redundancy. Only one router per subnet forwards traffic.

Answer 4

Virtual Router Redundancy Protocol (VRRP)

Question 5

GLBP is an FHRP that Cisco designed to allow multiple active forwarders to load-balance outgoing traffic on a per host basis rather than a per subnet basis like HSRP.

Answer 5

Gateway Load Balancing Protocol (GLBP)

Question 6

• Responds to default gateway ARP requests with the virtual router MAC address
• Assumes active forwarding of packets for the virtual router
• Sends hello messages between the active and standby routers
• Knows the virtual router IPv4 address

Answer 6

Active router functions

Question 7

• Sends hello messages
• Listens for periodic hello messages
• Assumes active forwarding of packets if it does not hear from active router
• Sends Gratuitous ARP message when standby becomes active

Answer 7

Standby router functions

Question 8

The router that is currently forwarding packets for the virtual router

Answer 8

Active router

Question 9

The primary backup router

Answer 9

Standby router

Question 10

The set of routers participating in HSRP that jointly emulate a virtual router

Answer 10

Standby group

Question 11

Command enables the HSRP router with the highest priority to immediately become the active router. Priority is determined first by the configured priority value, and then by the IPv4 address.

Answer 11

standby preempt

Question 12

Routers can simultaneously provide redundant backup and perform load sharing across various subnets and virtual local-area networks (VLANs).

Answer 12

Load balancing

Question 13

When a tracked interface becomes unavailable, the HSRP tracking feature ensures that a router with the unavailable interface will relinquish the active router role.

Answer 13

Interface tracking