What is the network VRRP protocol, and can it really solve network stability issues?

With the rapid development of the Internet, various value-added services (such as interactive network television IPTV, video conferencing, etc.) have begun to be widely deployed. The high reliability of the basic network has become the focus of users. For enterprise users, uninterrupted network transmission is particularly important. Enterprise networks are generally connected to the external network through routers. In large campus networks, the core layer of the network uses three-layer switches to achieve high-speed data forwarding and routing between VLANs. Routers and three-layer switches are key node devices in the network. In order to ensure the reliability of the network, they need to be redundantly backed up during network planning and design.

VRRP (Virtual Routing Redundancy Protocol) can achieve network redundancy backup

In the reliability networking of routers and switches, data forwarding of both the primary and backup devices is determined by the routing table of the upstream and downstream devices. This is because dynamic routing can dynamically adjust the routing table according to the link status and automatically forward data to the correct device. But what if the upstream and downstream devices are running static routing?

As shown in the figure below, the host sets the Router as the default gateway. When the host wants to access the external network, it will first send the message to the gateway, and then the gateway will pass it to the external network, thus realizing the communication between the host and the external network. Under normal circumstances, the host can fully trust the work of the gateway, but when the gateway fails, the communication between the host and the outside world will be interrupted.

If you want to solve the problem of network interruption, you need to add multiple gateways (Router1 and Router2 in the figure below). However, in general, the host cannot be configured with dynamic routing, and only one default gateway is configured. If we set Router1 as the default gateway, then when Router1 fails, the data cannot be automatically forwarded to Router2. At this time, we can only rely on manually adjusting the host's default gateway to Router2 to forward the host's data to Router2. However, this will inevitably lead to interruptions in the host's access to the external network, thereby affecting the normal operation of user services. Moreover, there are hundreds or thousands of hosts in large networks, and it is obviously impractical to achieve gateway backup by manually adjusting the network.

In order to better solve the problem of network interruption caused by gateway failure, network developers proposed the VRRP protocol.

VRRP (Virtual Router Redundancy Protocol) is a routing fault-tolerant protocol that can group multiple routing devices into a VRRP backup group, which is logically regarded as a virtual routing device. In the backup group, one routing device is used as the main routing device, and the others are used as backup routing devices. When the main routing device fails, VRRP will select one of the backup routing devices to become the new main device and take over the work of the failed device, thereby ensuring the continuity and reliability of network communications.

Application of VRRP Technology in Large Campus Networks

In addition to being used for backup of routers in the LAN connected to the external network mentioned above, VRRP technology can also be used for redundant backup of Layer 3 switches in the core layer of large campus networks.

In a large campus network, the core layer is at the center of the network, carrying a large amount of data exchange and responsible for routing between different VLANs. If the core layer equipment (such as the core three-layer switch) goes down, the entire network will be paralyzed. Therefore, when planning and designing a large campus network, the core equipment must have strong data exchange capabilities and high reliability.

At the same time, in order to improve the reliability of the core layer of large campus networks and avoid the entire network being paralyzed due to core layer equipment failure, another device is generally placed in the core layer as a backup for the main device. Once the main device fails, VRRP technology will immediately switch to the backup device to ensure the high reliability of the network core layer.

How VRRP Enhances the Stability of Large Campus Networks

As shown in the figure below, switch 1 and switch 2 form a VRRP backup group. Under normal circumstances, switch 1 acts as the master device (main switch) and is responsible for business forwarding; switch 2 acts as the backup device (standby switch) and does not forward business; but when switch 1 fails, switch 2 will become the new master device and continue to forward data for the host to ensure uninterrupted network.

Summarize

In a large campus network, for a network using a fixed gateway, when the gateway fails, in order to minimize the impact on users, the switching of the core layer three-layer switch needs to apply VRRP technology.