IP Connectivity // Lesson 05

First-Hop Redundancy.

Describe how first-hop redundancy protocols provide a resilient default gateway through a shared virtual IP and MAC address.

FHRPHSRPVRRPVirtual IPFailover
01 // Mental model

Start with the big picture.

Hosts normally configure one default gateway, which can become a single point of failure.

CCNA focus: Separate the physical router addresses from the virtual gateway. Client continuity depends on the group taking over the virtual identity, not on changing every host.
02 // Building blocks

Know what each part does.

01

The problem

Hosts normally configure one default gateway, which can become a single point of failure.

02

Virtual gateway

Multiple routers present a shared virtual IP and MAC address to clients.

03

Active forwarding

One device forwards for the group while another is ready to take over after failure.

04

Priority and preemption

Priority influences the preferred forwarder; preemption lets it reclaim the role after recovery.

03 // Compare and recognise

Read the clues.

ItemWhat to remember
HSRPCisco-developed FHRP using active and standby roles.
VRRPStandards-based FHRP using master and backup roles.
GLBPCisco FHRP that can distribute hosts across multiple active virtual forwarders.
Client viewThe host keeps using one virtual default-gateway address during router failover.
04 // Failure sequence

Failure sequence.

1. PC uses 10.10.10.1 as its default gateway
2. R1 is active and owns the group's virtual MAC
3. R1 fails; hello messages stop
4. R2 assumes the forwarding role
5. R2 answers for the same virtual IP and MAC
6. The PC keeps its configured gateway

Read the example from top to bottom, then verify the resulting state. Configuration is only complete when the output matches the intended design.

05 // Exam and troubleshooting

Turn facts into a method.

  • Cisco-developed FHRP using active and standby roles.
  • Standards-based FHRP using master and backup roles.
  • Cisco FHRP that can distribute hosts across multiple active virtual forwarders.
  • The host keeps using one virtual default-gateway address during router failover.
Exam checkpoint: Separate the physical router addresses from the virtual gateway. Client continuity depends on the group taking over the virtual identity, not on changing every host.
06 // Check yourself

First-Hop Redundancy quiz.

1. What address should clients use as their default gateway in an FHRP design?

2. What are the common HSRP forwarding roles?

3. What does preemption allow?

4. Which FHRP is standards-based?

5. What failure is FHRP primarily designed to remove?

Score: 0 / 5