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What is VRRP and Why Do We Need it?

Author Leslie

Date 02/01/2024

This article describes what VRRP is, its working principle and specific applications, so that you can have a deeper understanding of VRRP.

In today's enterprise networks and data centers, VRRP, as a crucial component to enhance the availability and redundancy of network devices, is becoming increasingly recognized. This article will provide you with a detailed explanation of what VRRP protocol is and why it is indispensable.

What is VRRP?

VRRP (Virtual Router Redundancy Protocol) is a network protocol designed to enhance the availability and redundancy of routers. It allows multiple routers to operate as a logical unit, sharing a virtual IP address and MAC address. In the event of a failure in the primary device, the operation swiftly switches to the backup device, ensuring continuous and reliable communication services. VRRP is commonly employed to establish redundant default gateways, guaranteeing that network devices can still access external networks if the primary router encounters a malfunction.

How Does VRRP Work?

VRRP has three states: Initialize, Master, and Backup. Only devices in the Master state can forward IP packets with virtual addresses. The Master state involves the election mechanism of the VRRP protocol. The VRRP backup group is a virtual router composed of multiple routers. In the VRRP group, multiple routers are elected based on the configured priority to determine a master device to work together. This master device is responsible for handling requests and data forwarding for all VRRP groups. The specific election mechanism is as follows:

Once the master device is elected, it shares a virtual IP address and MAC address with other routers. These virtual addresses are configured as the default gateway, serving the purpose of handling incoming and outgoing data traffic. The master and backup devices also periodically send VRRP advertisements to maintain their availability. These advertisements include status information of the VRRP group, such as device priority and IP address. The backup device monitors the status of the master device by receiving VRRP advertisements. If the backup device does not receive advertisements from the master device within a certain time, it considers the master device to have a failure and triggers a switchover. The backup device immediately takes over the virtual IP address and MAC address to ensure the seamless continuation of network traffic.

Why Do We Need VRRP?

With the rapid development of networks, enhancing device availability and redundancy has become a crucial aspect, particularly in applications such as enterprise networks, data centers, and ISPs. In these scenarios, there is a demand for networks to exhibit robust reliability and redundancy, ensuring rapid recovery in case of failures without disrupting data transmission. Therefore, to enhance the availability and redundancy of network devices, VRRP has been specifically designed in the telecommunication industry to ensure the transmission of network data.

VRRP protocol allows the formation of a virtual router group comprising multiple routers, with the election of a primary device responsible for handling data forwarding. In the event of a primary device failure, standby devices can swiftly take over their responsibilities, ensuring seamless network communication. Due to the presence of multiple standby devices, each with its priority, the potential impact of a single point of failure on the network is mitigated, thereby enhancing network redundancy.

VRRP Application

Master/Backup

In the master-backup mode, only the device in master mode can receive and forward packets. When the master device fails, a new master will be promptly elected from the backup devices based on the configured priorities. This mode involves multiple routers forming a VRRP backup group, where each router in the group has a different priority. The device with the highest priority becomes the master.

Load Sharing

A router can join multiple VRRP backup groups, each with different priorities. This router can act as a backup in one group while serving as a master in another group. It's important to note that load-sharing mode requires at least two VRRP backup groups, each with one master device and multiple backup devices. For example:

In VRRP Group 1, Router A acts as the master, while Routers B and C serve as backups. In VRRP Group 2, Router B is the master, and Routers A and C are backups. In VRRP Group 3, Router C is the master, and Routers A and B are backups. To achieve load sharing between them, the virtual IP addresses of VRRP backup groups 1, 2, and 3 need to be configured as the default gateway IP addresses for hosts within the subnet. Additionally, Routers A, B, and C should have the highest priorities in VRRP backup groups 1, 2, and 3, respectively.

Conclusion

VRRP, as a network protocol designed to enhance the availability and redundancy of network devices, is primarily used in environments where network availability requirements are high, and there is a need to prevent single points of failure while achieving device redundancy and rapid switching. This protocol prevents situations where data transmission is disrupted due to the failure of a single device. If you have any questions about the VRRP, please feel free to contact QSFPTEK's CCIE/HCIE engineers at support@qsfptek.com.

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