Introduction to HSRP Hot Standby Protocol

The so-called hot backup routing protocol (HSRP) is designed to provide us with such a mechanism. It is designed to support uninterrupted services when IP transmission fails. Specifically, this protocol is used to prevent the failure of the first hop route when the source host cannot dynamically learn the IP address of the first hop router. It is mainly used for multi-access, multicast, and broadcast LAN, such as Ethernet ).

Of course, HSRP is not intended to replace the existing dynamic routing discovery mechanism, and these existing routing protocols can still be used, but not in any possible situation. In the past, most hosts did not support the dynamic routing discovery protocol. They work by configuring the default routing. However, HSRP provides them with a failure service mechanism. All the routers involved in HSRP are assumed to have configured the appropriate IP routing protocol, there are also several routes.

The purpose of the hot backup routing protocol (HSRP) is to make the host look like it only uses one vro, and maintain the connectivity of the route even if the current first hop router fails. All vrouters involved in this Protocol are mapped to a virtual router. This protocol guarantees that only one vro sends packets on behalf of the vro. The terminal sends data packets to the vro. The router of the forwarding packet is changed to a live router. If the active router cannot work for some reason at some time, the backup router will be chosen to replace the original active router. This Protocol provides a mechanism for defining Active Routers and backup routers. Use the IP address on the router designed by the Protocol. If the active router fails, the backup router will immediately replace the active router without causing a major interruption to the host's connectivity.

When using HSRP, the work of a group of routers will be consistent as the work of a virtual router connecting the LAN to the host. This group of routers is called an HSRP group or a backup group. In this group, a vro is selected to forward data packets sent from the host to the vro. This router is called a live router. Another vro will be selected as a backup vro. If the active router fails, the backup router will be responsible for the packet forwarding function of the active router. Even if you can specify the number of routers running HSRP at will, only the active router can forward the data packets sent to the virtual router.

To minimize network congestion, only Active Routers and backup routers in the network can send an HSRP message packet after the HSRP protocol is selected. If the active router fails, the backup router replaces it as a new active router. When the backup router fails or becomes a live router, the other router will be selected as the backup router.

In a LAN, multiple hot standby groups can coexist and overlap. Each backup group imitates a vro. Each backup group has a known MAC address and an IP address. This IP address should be the address in the first subnet of the LAN, but it must be different from the address set on all router ports and the address of the host in the LAN, it even includes addresses set for other HSRP groups.

If multiple HSRP groups are set in a LAN, assigning hosts to different backup groups will cause network load explosion.