FHRP

• First Hop Redundancy Protocols use a Virtual IP (VIP) and MAC addresses to allow for automated failover
• The network clients use the VIP as their Default Gateway
  • If a physical gateway fails, another gateway will take over

FHRP Virtual MAC Addresses

• Virtual MAC addresses
  • HSRPv1: 0.c07.acXX or 00:00:0c:07:ac:XX
    • 0C7AC
  • HSRPv2: 0.c9f.fXXX or 00:00:0c:9f:fX:XX
    • 0C9FF
  • VRRP: 0.5e00.1XX or 00:00:5e:00:01:XX
    • V = 5e00
    • 05e001 (Oh 5-ee hundred and 1)
  • GLBP: 7.b400.XXYY or 00:07:b4:00:XX:YY
    • G =/= 5, so G = b400
    • 7B400

FHRP Multicast Addresses

• 224.0.0.2
  • HSRPv1
• 224.0.0.9
  • RIP
• 224.0.0.18
  • VRRP
• 224.0.0.102
  • GLBP
  • HSRPv2

FHRP Protocols

1. Hot Standby Router Protocol (HSRP)

   1. #Cisco-Proprietary ; deployed in active/standby pairs
   2. This is what's covered in the CCNA

2. Virtual Router Redundancy Protocol (VRRP)

   1. Open standard; deployed in active/standby pairs
   2. Almost identical to HSRP.
      1. One difference is HSRP uses "standby" and VRRP uses "vrrp"

3. Gateway Load Balancing Protocol (GLBP)

   1. #Cisco-Proprietary ; supports active/active load balancing across multiple routers on the same subnet

4. FHRP-activated routers communicate with each other by sending multicast Hello messages

5. When FHRP is configured, the Virtual IP address should be configured as the default gateway for hosts

6. The active FHRP router responds to ARP requests with a virtual MAC address

7. HSRP uses Active and Standby routers

   1. When HSRP Standby router switches to active, it will send Gratuitous ARP messages
   2. The HSRP active router is determined by Highest priority, then highest IP address
      1. The default priority is 100
   3. HSRPv1
      1. HSRPv1 Mutlicast address is 224.0.0.2
      2. Virtual MAC address format: 0000.0c07.acXX
         1. (XX is HSRP group number)
         2. This can be shortened to 0.c07.acXX
   4. HSRPv2
      1. HSRPv2 Multicast address is 224.0.0.102
      2. Virtual MAC address format: 0000.0c9f.fXXX
         1. (XXX is the HSRP group number)
            1. This can be shortened to 0.c9f.fXXX
   5. HSRP Commands
      1. Assign virtual IP
         1. Config-if# standby (group number) ip (IP address)
      2. Configure priority
         1. Config-if# standby (group number) priority (Priority number)
      3. Configure Preemption
         1. Config-if# standby (group number) preempt
      4. Configure Version 2
         1. Config-if# standby version 2

8. VRRP uses Master and Backup routers

   1. VRRP Multicast address is 224.0.0.18
   2. VRRP Virtual MAC address format is 0000.5e00.01XX
      1. (XX = VRRP group number)
      2. This can be shortened to 0.5e00.1XX

9. Gateway Load Balancing Protocol

   1. Load balances among multiple routers on the same subnet
      1. A single Active Virtual Gateway (AVG) is elected
      2. The AVG assigns up to four Active Virtual Forwarders (AVFs)
   2. GLBP - Gateway Load Balancing Protocol - Cisco Systems
   3. GLBP Multicast address is the same as HSRPv2, 224.0.0.102
   4. GLBP virtual MAC address format is 0007.b400.XXYY
      1. This can be shorted to 7.b400.XXYY
      2. (XX = GLBP group number, YY = AVF number)
      3. AVF = Active Virtual Forwarders

Metadata

OSI or TCP/IP Layer

CCNA Exam Topic

#extop-3-5

Contributors

Sources