What is the Hot Standby Router Protocol (HSRP)

Summarize of the HSRP

HSRP (Hot Standby Router Protocol): is a Cisco WS-C2960S-48FPS-L Price proprietary, it ensures that the network edge device or access link fails, the user can quickly recover and transparentcommunication, providing redundancy for the IP network. Hot standby routing protocol for the IP network to provide fault tolerance and enhanced routing function. By using a virtual IPaddress and the virtual MAC address, LAN segment of two or more router can act as a virtual router providing service.

Group members of the HSRP 

HSRP backup is a backup active router, a router, a virtual router to other routers.

The active router: the main function is to the virtual router packet forwarding. Another routerin the group is selected as the backup router. The active router by sending Hello messages to take and keep it active role.

Backup router: as long as the function is to monitor the operation of the HSRP group, and to the active router cannot run, quickly assume packet forwarding responsibility. Backup routercan transmit Hello message, inform the role and state change all routers in the backup router group.

Virtual Router: the main function is to the end user with a continuous working router. Virtual router configuration has its own IP address and MAC address, but not the actual packet forwarding.

Other routers: these routers to monitor the Hello message, but no response. The routerforwarding any through their packets, but not through the virtual router packet forwarding.

The principle of the HSRP

Each router in the HSRP group has the specified priority, priority degree evaluation forrouters in the active router selection in. The default priority 100 (configurable range 0-255),group of highest priority router will become the active router, then the backup router. When the priority under the same conditions, the router LAN port IP address, the address will become the active router.

When the terminal users to submit data to the virtual router, will be processed by the active router, when the active router fails, the backup router will assume the active router work in seconds, then the backup became active router, and the backup router vacancies within the group, other routers will be promoted backup router, in time select the backup router priority.

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