This article is to identify the important information to know about the the three (3) First Hop Redundancy Protocols (FHRP) supported on a Cisco devices.
The three FHRP are:
- HSRP – Hot Standby Redundancy Protocol
- VRRP – Virtual Router Redundancy Protocol
- GLBP – Gateway Load Balancing Protocol
HSRP
- The virtual mac address are as follows based on version:
- v1: 0000.0c07.acXX
- v2 : 0000.0c9f.f000 – 0000.0c9f.ffff
- sends hello message every 3 seconds to multicast address on port UDP 1985:
- 224.0.0.2 (v1)
- 224.0.0.102 (v2)
- Preemption is disabled by default
- The HSRP virtual IP address cannot be the same as any of the devices in the group
- The group number can be the same on the different interfaces on a device
- v1 group range 0 – 255
- v2 group range 0 – 4095
- If the priority is equal on all devices in a group, the device with the highest IP address wins.
- v1 and v2 are not interoperable
- Router state are either Active or Standby
VRRP
- This protocol is an IEEE standard
- The virtual mac address is 0000.5e00.01RR (R represents the virtual router identifier)
- sends hello message every 1 second to multicast address 224.0.0.18 via IP protocol 112
- Preemption is enabled by default
- Router state are either Master or Backup
- Protocol has the option to learn timer from the Master
- vrrp # timer learn
GLBP
- the virtual MAC address is 0007.b400.GGFF (G is the GLBP group number and R is the AVF number)
- sends hello message every 3 seconds to multicast address on port UDP 3222:
- 224.0.0.102
- All devices will be an AVF (Active Virtual Forwarder)
- Only one AVG (Active Virtual Gateway) will be elected
- The AVG assign a virtual MAC address to the AVF
- AVG is responsible for responding to ARP requests for the virtual IP address
- load balancing methods
- round-robin (default)
- host-dependent
- weighted
- preemption is disabled by default
- GLBP uses 3 packet types: Hello, Request and Reply
The detail listed is not exhausted but it will be updated in the future.
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