First-hop redundancy protocol

{{short description|Computer networking protocol allowing first hop fallback on router failure}}

First hop redundancy protocols (FHRP) are a category of networking protocols designed to protect the default gateway used on a subnetwork by allowing two or more routers to provide backup for that address.{{cite web |url=https://www.ciscopress.com/articles/article.asp?p=3197440 |title=First Hop Redundancy Protocols |date=5 August 2024 |author1=Wendell Odom |author2=Jason Gooley |author3=David Hucaby |publisher=Cisco Press |quote=The term First Hop Redundancy Protocol (FHRP) refers to the category of protocols that enable hosts to take advantage of redundant routers in a subnet.}}{{Cite web|url=https://www.cisco.com/c/en/us/products/ios-nx-os-software/first-hop-redundancy-protocol-fhrp/index.html|title=First Hop Redundancy Protocol (FHRP)|website=Cisco|language=en|access-date=2019-06-05}}{{Cite web|url=https://ipcisco.com/lesson/first-hop-redundancy-protocols/|title=First Hop Redundancy Protocols|last=gokhankosem|date=2018-10-16|website=IpCisco|language=en-US|access-date=2019-06-05}} In the event of failure of an active router, the backup router will take over the address, usually within a few seconds. In practice, such protocols can also be used to protect other services operating on a single IP address, not just routers.

Examples of such protocols include (in approximate order of creation):

• Hot Standby Router Protocol (HSRP) - Cisco's initial, proprietary standard developed in 1998{{Cite web|url=https://www.petri.com/cisco-first-hop-redundancy-protocols|title=Cisco Protocols: HSRP, VRRP, GLBP|date=2012-04-11|website=Petri|language=en-US|access-date=2019-06-05}}
• Virtual Router Redundancy Protocol (VRRP) - an open (albeit patent-encumbered) standard protocol based largely on Cisco's HSRP
• Common Address Redundancy Protocol (CARP) - patent-free, unencumbered alternative to Cisco's HSRP and the IETF's VRRP, developed in October 2003
• Extreme Standby Router Protocol (ESRP) - Extreme Networks' proprietary standard with fast failover and layer 2 protection
• Gateway Load Balancing Protocol (GLBP) - a more recent proprietary standard from Cisco that permits load balancing as well as redundancy
• Routed Split multi-link trunking (R-SMLT) - an Avaya redundancy protocol
• NetScreen Redundancy Protocol (NSRP) - a Juniper Networks proprietary router redundancy protocol providing load balancing
• Chassis Cluster Redundant Ethernet - a Juniper Networks proprietary Ethernet redundancy protocol, used on its SRX platform{{Cite web|url=https://www.juniper.net/documentation/en_US/junos/topics/topic-map/security-chassis-cluster-redundant-ethernet-interfaces.html|title=Chassis Cluster Redundant Ethernet Interfaces - TechLibrary - Juniper Networks|date=2019-05-30|website=Juniper Networks|language=en-US|access-date=2019-06-09}}
• Multi-active Gateway Protocol (MAGP) - a Mellanox proprietary protocol based on VRRP that allows active-active operation{{Cite web|last=|first=|date=1 March 2020|title=HowTo Configure MAGP on Mellanox Switches|url=https://community.mellanox.com/s/article/howto-configure-magp-on-mellanox-switches|archive-url=|archive-date=|access-date=|website=community.mellanox.com}}