Routing And Switching Questions Long
HSRP (Hot Standby Router Protocol) is a Cisco proprietary protocol that provides redundancy in network routing by allowing multiple routers to work together as a virtual router. This virtual router is represented by a single IP address and MAC address, known as the virtual IP address (VIP) and virtual MAC address (VMAC) respectively. HSRP ensures high availability and fault tolerance in a network by allowing one router to act as the active router, while the other routers remain in standby mode.
The process of HSRP involves the following steps:
1. Router Election: In a group of routers configured for HSRP, one router is elected as the active router, and the others become standby routers. The election is based on the priority value assigned to each router, with the highest priority router becoming the active router. If two routers have the same priority, the router with the highest IP address is elected as the active router.
2. Active Router: The active router assumes the responsibility of forwarding traffic for the virtual IP address. It actively participates in the routing process and responds to ARP requests for the virtual MAC address. It also periodically sends HSRP hello messages to the standby routers to inform them of its status.
3. Standby Routers: The standby routers monitor the status of the active router by receiving the hello messages. If the standby routers do not receive a hello message from the active router within a specified time interval, they assume that the active router has failed and initiate an election process to select a new active router.
4. Virtual Router: The virtual router, represented by the VIP and VMAC, provides redundancy in network routing. When a device in the network wants to communicate with the virtual IP address, it sends an ARP request for the virtual MAC address. The active router responds to this ARP request, and the device forwards its traffic to the active router.
5. Failover: In the event of a failure of the active router, one of the standby routers takes over as the new active router. This failover process is seamless and transparent to the devices in the network. The new active router assumes the responsibility of forwarding traffic for the virtual IP address, while the other routers remain in standby mode.
HSRP provides redundancy in network routing by ensuring that there is always an active router available to handle traffic for the virtual IP address. This helps to prevent network downtime and ensures continuous connectivity for devices in the network. Additionally, HSRP allows for load balancing by distributing traffic among multiple routers in the standby group.