Cisco’s Hot Standby Router Protocol (HSRP) is a redundancy protocol designed to provide high availability for IP networks. It ensures continuous network operation even if one or more routers fail. HSRP achieves this by allowing two or more routers to work together in a group, with one router designated as the active router and others as standby routers.

Active Router: The router in the HSRP group that forwards packets sent to the virtual IP address.
Standby Router: A router that takes over the active role if the active router fails.
Virtual IP Address: An IP address shared between the routers in the HSRP group. It’s configured as the gateway IP for devices on the local network.
Priority: A value used to determine the router that becomes the active router. The router with the highest priority becomes the active router.
Hello Messages: Periodic messages exchanged between routers in the HSRP group to maintain group membership and status.


Configuration:

Here’s a step-by-step guide to configuring HSRP on Cisco routers:

1. Access Configuration Mode:
   Access the router’s command line interface (CLI) using Telnet, SSH, or a direct console connection.
   
   
2. Enter Global Configuration Mode:
   enable
   configure terminal
   
   
3. Configure HSRP:
   interface <interface_name>
   standby <group_number>
   ip <virtual_ip_address>
   standby <group_number>
   priority <priority_value>
   standby <group_number> preempt
   
   Replace <interface_name> with the interface connecting to the LAN.
   <group_number> is a unique identifier for the HSRP group (range 0-255).
   <virtual_ip_address> is the IP address shared by routers in the HSRP group.
   <priority_value> is the priority of the router (range 1-255). The default is 100.
   preempt enables the router to take over the active role if its priority becomes higher than the current active router.
   
   
4. Verify Configuration:
   show standby brief
   

HSRP is a powerful redundancy protocol that enhances network reliability by providing automatic failover in case of router failure. By configuring HSRP on Cisco routers, you can ensure uninterrupted network connectivity for your users and applications.