The principle and application of Cisco Thermal Backup protocol

HSRP Introduction:

HSRP (HOST STANDBY ROUTER PROTOCOL), also known as the Hot Backup protocol. Cisco platform is a proprietary technology, Cisco's private protocol. HSRP runs on UDP, using port number 1985.

The principle of the hot backup protocol:

The protocol contains multiple routers, corresponding to the HSRP group. Only active routers in this group assume the responsibility of forwarding user traffic. When the active router fails, the backup router assumes the responsibility, called the new active router. When there are multiple hot backup groups on a local area network, the host cannot be divided into different hot-backup groups, and the load can be balanced. In this protocol, a virtual IP address is established as the default gateway of the network system, and no connection interruption occurs when the active router fails. A virtual gateway that is used on the host. You do not need to change the gateway when there is a problem with routing in the link.

Advantages of HSRP:

The arch has a redundant network that provides load balancing and enables high availability of the network.

The role that the router assumes:

Active routers: The router that is responsible for forwarding packets throughout (active Router) is called the active router.

Backup routers: All called (Standby Router) is responsible for backing up the primary router and converting it to the active router role once the primary router fails.

The specified scenario for the role:

The HSRP protocol uses a priority scheme to determine which routers configured with the HSRP protocol become active routers. If a router's priority is set higher than all other routes, the route is an active route. When an active route is down or a single point of failure occurs, the active route is again elected in the backup route according to the priority level. The larger the number, the higher the priority.

Routers with the HSRP protocol are configured to exchange the following three multicast messages:

hello--notify the router to send its own HSRP priority and status information, which is sent every 3 seconds by default.

coup--sends coup messages when a standby router is called an active router.

resign--sends this message when the active router is down or if it has a higher priority router.

Routers configured with the HSRP protocol have the following States:

INITIAL--HSRP the state at boot time, HSRP is not yet running. Typically, the state of the configuration or the port just started is changed.

The listen--router has been given a virtual IP address, waiting for active and passive routing to send the Hello packet, when the router is neither an active route nor a passive route.

speak--This state, the router sends the Hello message on a regular basis. The wait ratio determines the role of the individual routers in the priority level between them.

standby--as a backup router. If the active route is down or a single point of failure occurs, the backup router is started.

active--as an active router. Transfer packets.

Case: