FHRP Options
The FHRP used, largely depends on the equipment and requirements of the present network
| HSRP – Hot Standby Router Protocol |
| HSRP is a Cisco-Proprietary FHRP protocol which was designed to for transparent failover of a first-hop IPv4 device. HSRP is used in a group of routers by electing an active router and a standby router. The active router is the router that is used to route packets. On the other hand, the standby router is the one that takes over when the active router fails or when pre-set conditions are met. The standby router in an HSRP methodology is to constantly monitor the operational state of the HSRP group and quickly assume packet forwarding responsibilities when the active router fails |
| HSRP for IPv6 |
| This is the same as HSRP but in an IPv6 environment. This method of HSRP has a virtual MAC address which is derived from the Group number and instead of an IPv4 address, this HSRP method uses an IPv6 link-local address which is derived from the HSRP virtual MAC Address. Router Advertisement Messages (RA) are sent periodically for the HSRP virtual IPv6 link-local address when the group is active. If the group become inactive, such RA messages will stop after sending the final RA |
| VRRPv2 – Virtual Router Redundancy Protocol Version 2 |
| Unlike HSRP, this protocol is a non-proprietary election protocol that dynamically assigns responsibilities to one or more virtual routers to the VRRP routers within an IPv4 LAN. This protocol also allows several routers to use the same virtual IPv4 address. A VRRP router is configured to run the VRRP protocol in conjunction with one or more other routers attached to a LAN. One router is elected as the virtual router master, whilst all the other routers will act as backup routers in case the virtual router/master fails |
| VRRPv3 – Virtual Router Redundancy Protocol Version 3 |
| This is the same as VRRPv2 but it also supports IPv6 addressing. This protocol can operate in a multi-vendor environment and is way more scalable than VRRPv2 |
| GLBP – Gateway Load Balancing Protocol |
| This also is a Cisco-Proprietary FHRP that protects from router failures like HSRP and VRRP, but in the meantime, this is an HSRP protocol that allows load-balancing/load-sharing between a group of redundant routers |
| GLBP for IPv6 |
| This is the same as GLBP but it also supports IPv6 addressing. GLBP for IPv6 provides automatic router backup for IPv6 configured hosts with a single default gateway on a LAN. |
| IRDP – ICMP Router Discovery Protocol |
| This is a legacy FHRP protocol specified in RFC 1256 IRDP allows IPv4 hosts to locate other routers that provide IPv4 connectivity to other IP networks via ICMP |