Port 1985
HSRP
The Hot Standby Router Protocol (HSRP) is a Cisco proprietary redundancy protocol designed to ensure high network availability by providing automatic failover to a backup router in case the primary router becomes unreachable, thereby maintaining uninterrupted communication within a network..
Technical Details
Cisco’s Hot Standby Router Protocol (HSRP) operates as a first-hop redundancy protocol designed to minimize network downtime caused by router failures. It is primarily used in networks implementing Cisco equipment to enable failover and ensure continuous gateway availability.
HSRP works by configuring a group of routers to present a single virtual IP address and virtual MAC address to hosts on the local subnet. One router is elected as the Active router, while another acts as the Standby router. The Active router handles all routing for the virtual IP address, while the Standby cautiously monitors its status.
Routers in the HSRP group communicate using multicast UDP packets on port 1985, exchanging hello messages to track network status. If the Active router fails, the Standby router takes over nearly instantaneously. Multiple standby routers can be arranged with priorities to determine failover order, enhancing network resilience.