First Hop Redundancy Protocol (FHRP) and its Types

In order to protect their networks against complete breakdown, businesses use a number of different protocols. First Hop Redundancy Protocol (FHRP) is one such protocol, and it uses a virtual default gateway to provide nearly uninterrupted network availability for businesses. FHRP allows multiple routers to act as a backup for each other in case one of them fails or becomes unreachable. This way, the network can avoid losing connectivity to the default gateway and ensure uninterrupted traffic flow. In this blog, we will mainly focus on the basic meaning of the First Hop Redundancy Protocol (FHRP) and why it is important for network reliability and performance. We will also learn about the different types of FHRP, such as Hot Standby Router Protocol (HSRP), Virtual Router Redundancy Protocol (VRRP), and Gateway Load Balancing Protocol (GLBP). Before learning about FHRP (First Hop Redundancy Protocol), a network engineer must understand why redundancy is even required in networking. Redundancy plays a vital role in networking. Network redundancy assures business continuity by avoiding failure of the network. By keeping operations running all the time, it boosts productivity. To have a dependable network, we must build a redundant one. In local area networks (intranet), we use multiple switches for redundancy. But is it possible for multiple routers too? Yes, it is also possible to have redundant topology to connect different networks together. Every host connected to the organization’s network must use a router, which acts as the host’s default gateway to the Internet. But what happens if the gateway router is unavailable? Hosts can have only one default gateway configured at a time, so when that router fails, hosts will lose connectivity. We need to replace the gateway router and also need to configure default gateway on every host. This approach is ineffective because it will result in longer service interruptions for the organization’s users. That is where FHRP steps in. First Hop Redundancy Protocol (FHRP) is a hop redundancy protocol designed to provide redundancy to the gateway router within the organization’s network by using a virtual IP address and virtual MAC address. So, in case of a failure of the gateway, the backup router will become active, usually within a few seconds. If the default router goes offline, the backup router will take its place to be the gateway router for all the hosts without changing the default gateway address of every host. The below diagram is an example of a network topology without FHRP implementation: The below diagram is an example of network topology with FHRP implemented: Let’s understand the importance of First Hop Redundancy Protocol with help of an example: Imagine you are trying to access a website, but the router responsible for forwarding the traffic suddenly fails. Now, this failure can lead to network downtime, which can disrupt users and services. With redundancy in place, this can be avoided. Hence, FHRP is used. It will instantly switch to a backup router in case of a failure, ensuring no interruptions in the services. FHRP is a protocol used in computer networks that acts as a backup for the default gateway on a subnetwork. The default gateway is the router that connects the subnetwork to other networks, such as the Internet. In case of the failure of the default gateway, the subnetwork will lose connectivity to other networks, which further causes interruption and network downtime. To avoid this, FHRP enables several routers to share a single virtual IP and virtual MAC address that acts as the default gateway for hosts inside a subnetwork. All traffic entering and leaving the subnetwork is routed via one of these routers, which is identified as the active router. The other routers are backups that keep an eye on the primary router to take over if necessary. So, the working of FHRP can be divided into 3 parts: FHRP works by setting up a “failover” mechanism between routers. An active router is responsible for the network traffic in normal circumstances. However, when it fails, a standby router automatically takes over the responsibility without disrupting the network services. FHRP uses the concept of virtual router. When configured, routers create a virtual IP address that devices in the network use as their gateway. This virtual router is mapped to multiple physical routers to provide seamless failover. During setup, FHRP recognises an active router that is handling the network traffic. The rest of the routers are kept as backup or standby routers, which constantly monitor the active router’s status. In case of a failure, the backup routers are ready to take over instantly. The prime purpose of the First Hop Redundancy Protocol is to provide redundancy to your network by enabling multiple routers as a gateway for your traffic. This allows your network to continue working even in case of a router failure, as another router will take over instantly. Here are FHRP’s core objectives: The primary function of FHRP is to ensure a backup router is always ready to take over in case of active router failure. This minimizes the risk of network failure due to the failure of one router. When a router failure happens, FHRP allows the network to instantly switch to a standby router without the users noticing any disruptions. It reduces downtime and helps keep business operations running smoothly. Below, we have taken an example to help you understand the purpose of FHRP. Topology: Normal Operation: Router A Fails: In this case, the FHRP guarantees the client internet access even if Router A is unavailable, i.e., fails. Router B then becomes the new primary router and uses the same IP address and the client does not have to change anything to remain connected. There are three ways to implement FHRP. Examples of these protocols are: Let’s discuss each one of these, one by one. Let’s start with HSRP. Hot Standby Router Protocol or HSRP is a Cisco-proprietary router redundancy protocol that enables a group of routers to cooperate to have a redundant network. All the routers within the group will have the same virtual IP address and virtual mac address. The Two router states of Hot Standby Router Protocol (HSRP) are: Where, 0000.0c = Cisco ID 07.ac = HSRP ID xx= Group Number For Example – For HSRP group number 10, the virtual MAC address will be 0000.0c07.ac0A HSRP’s problem is that at any given time, only one router will be active. The other router is on standby until the active router fails. This plan of action is not particularly effective because all of the extra bandwidth offered by redundant uplinks connected to standby routers will not be utilised. VRRP stands for Virtual Router Redundancy Protocol. It is a vendor-neutral redundancy protocol that groups two or more routers to produce a new single virtual router. It allows for redundancy by assigning the same virtual gateway IP address and MAC address to all physical routers in the VRRP group. Currently, VRRP is at version 2. It’s almost the same idea as HSRP. The only difference is that on VRRP, preemption is enabled by default, whereas on HSRP, it must be configured manually. Note – If we want a specific router to always assume the role of an Active HSRP Router whenever it’s up and running, then we can use HSRP Preempt. Two states of Virtual Router Redundancy Protocol (VRRP) are: It is currently the organization’s default gateway for all hosts. It is constantly sending and receiving packets to and from the hosts. During a failover or when the master router goes offline, the backup router will take over as the master router. GLBP stands for Gateway Load Balancing Protocol. It prevents a single point of failure, like HSRP and VRRP. Still, it also allows load-sharing among a group of redundant routers so that all the routers will take an active part in packet forwarding, and no uplink will be unused. This is the additional feature of GLBP protocol with redundancy. Where, xx.xx = GLBP group Number and yy = virtual Forwarder number. For Example – GLBP group number 1 and forwarder 1 has virtual MAC address: 0007.b400.0101 Some of the benefits of using the First Hop Redundancy Protocol (FHRP) are: Here are some FHRP best practices: When setting up FHRP, you must configure redundancy to ensure a smooth failover process, or you will notice a small downtime error during failover. Monitoring your FHRP setup regularly is extremely important to ensure that the routers are functioning as expected. Periodic maintenance and testing can help you to mitigate any potential issues before they create any failures. It is a network protocol that allows a router to act as a backup for another router in case of failure. FHRP can also be used to improve the availability as well as reliability of network traffic. The three types of FHRP protocols are Hot Standby Router Protocol (HSRP), Virtual Router Redundancy Protocol (VRRP), and Gateway Load Balancing Protocol (GLBP). All of these protocols mentioned above are designed to provide redundancy and load balancing for the default gateway used on a subnetwork. It is done by allowing two or more routers to share a virtual IP address and a virtual MAC address. VRRP stands for Virtual Router Redundancy Protocol, and it is similar to HSRP, but it supports more than one virtual router per interface. Whereas, GLBP stands for Gateway Load Balancing Protocol, and it extends the functionality of HSRP and VRRP by allowing load balancing among multiple active routers in a group. There are many benefits of using FHRP. Some of these are: In this blog, we have explained First Hop Redundancy Protocol, its working, and the types of FHRP protocols. Apart from that, we have added some of the most asked questions for your clear understanding. We hope you have learned, and if you have any further questions or suggestions, feel free to comment below. If your goal is to master these protocols, you should enrol in our CCNA training. This training course will not only introduce you to the networking world but also help you master most of the networking protocols.Introduction
Why Redundancy?
First Hop Redundancy Protocol (FHRP)
Why is FHRP Important?
Working of FHRP
Router Failover Mechanism
Virtual Router Concept
Election of Active and Standby Routers
What is the purpose of Fist Hop Redundancy Protocol?
Ensuring Network Availability
Minimizing Downtime
Types of First Hop Redundancy Protocol (FHRP)
Hot Standby Router Protocol (HSRP)
HSRP features
Virtual Router Redundancy Protocol (VRRP)
Master Router
Backup Router
Gateway Load Balancing Protocol (GLBP)
GLBP Operation
GLBP Features
What are the benefits of using FHRP?
FHRP Best Practices
Configuring Redundancy Effectively
Monitoring and Maintenance
Frequently Asked Questions
Q1. What is FHRP used for?
Q2. What are the three types of FHRP protocols?
Q3. What is VRRP and GLBP?
Q4. What is the benefit of FHRP?
Conclusion