• atulsharma.cse@gmail.com
• January 6, 2023
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The First Hop Redundancy Protocol (FHRP) works on ‘redundancy’ which means a network must have at least two routers in case of any network crash.

In the previous blog, we learned about the FHRPs in detail. I definitely recommend you go through that blog before jumping to this blog.

As we have learned previously that the FHRPs are redundant protocols. This means that they are highly available. This could be explained as such. In a network, if all the host PCs are connected to a single router to send the traffic, the whole network crashes if the router crashes.

However, if there is another standby router in the network, it can substitute the failed active router for the smooth functioning of the network. Therefore, the First Hop Redundancy Protocols (FHRPs) make it possible for big enterprise networks to work smoothly.

As we have learned before, the FHRP is not a specific protocol. It refers to a variety of redundancy protocols. In this blog, we will learn about these varieties of protocols.

The Three Main Types of FHRPs

As discussed earlier, FHRPs are a class of protocols. There are many varieties of FHRPs. However, from CCNA 200-301 exam point of view, it is essential that you learn the three main types of FHRPs. These are:

• HSRP (Hot Standby Router Protocol)
• VRRP (Virtual Router Redundancy Protocol)
• GLBP (Gateway Load Balancing Protocol)

Let us now start learning about all three routing protocols one by one. Remember that these have the same characteristics as the FHRPs because they belong to the same family.

1. Hot Standby Router Protocol (HSRP)

Here are some of the critical features of the HSRP protocol:

• • The HSRP only runs on Cisco devices as it is a Cisco proprietary. For example, it cannot run on Juniper routers.
  • In HSRP, an active and standby router is chosen.
  • There are two versions of HSRP:

• Version 1
• Version 2: It adds IPv6 support and increases the number of groups that can be configured.
• In networks where there are multiple subnets and VLANs, we need to configure a virtual IP address for each subnet as each subnet needs its own default gateway.
• Each of the virtual IPs is configured in a different HSRP group.
• As we studied earlier, the active and standby routers send each other “Hello” messages.
• These multicast IPv4 addresses are as follows:
  • V1 = 224.0.0.2
  • V2 = 224.0.0.102
• The virtual MAC addresses are as follows:
  • V1 = 0000.0c07.acXX (XX = HSRP group number)
  • V2 = 0000.0c9f.fXXX (XXX = HSRP group number)
• Therefore, the virtual MAC address for HSRP group 1 will be 0000.0c07.ac01 because the group number is 1.
• In networks consisting of multiple subnets or VLANs, subnets or VLANs can be load balanced by a different active router in each subnet.

2. Virtual Router Redundancy Protocol (VRRP)

Here are the key features of the VRRP protocol:

• VRRP is an open standard protocol. It is not a Cisco-owned protocol. Therefore, it can be used on devices from any maker.
• The VRRP is quite similar to HSRP in functionality.
• A master and backup router are chosen instead of an active and standby router.
• The IPv4 multicast address used is 224.0.0.18.
• The format of the virtual MAC address is 0000.5e00.01XX (XX = VRRP group member).
• Although VRRP cannot perform load balance in the same subnet as HSRP, it can load balance between different subnets by configuring different master routers in each subnet.

3. Gateway Load Balancing Protocol (GLBP)

The main features of the GLBP are as follows:

• The GLBP is a bit different protocol from the HSRP and VRRP.
• Just like HSRP, it is a Cisco-owned protocol. Therefore, it can only run on Cisco devices.
• It load balances among multiple routers within a single subnet.
• For example, if PC1 and PC2 are both in the same VLAN1, PC1 can use router0 as its default gateway and PC2 can use router1 as its default gateway.
• A single Active Virtual Gateway (AVG) is chosen for the subnet.
• Each AVG can choose up to 4 Active Virtual Forwarders (AVFs). In fact, even an AVG can act as an AVF.
• Each of the chosen AVF acts as a default gateway for a section of hosts in the subnet.
• Therefore, load balancing can be done within a single subnet.
• The multicast IPv4 address is 224.0.0.102. It is the same as HSRP version 2.
• The virtual MAC address is 0007.b400.XXYY (XX = GLBP group number, YY = AVF number).

What is the Difference Between The Three Protocols?

Now that you are familiar with all three main varieties of FHRPs. It is time to understand the major differences between these three protocols!

Make sure that you remember these major differences between the three versions of the FHRP. 

Bottom Line

This marks the end of our blog. So in this blog, you have learned about the three main varieties of the First Hop Redundancy Protocol (FHRP). Make sure that you learn the key differences between these three protocols to ace the CCNA 200-301 exam.

It is not important to learn how to configure these three protocols from the CCNA exam point of view. If you are really interested to learn the configurations, you can enroll in our CCNA course. Don’t forget to check our official website!

Stay tuned for more blogs in the CCNA series! 

Happy Learning