First Hop Redundancy Protocols

First Hop Redundancy Protocols

1. 1. HSRP

   • 9. Hot Standby Router Protocol
   • 10. First Hop Redundancy Protocol
   • 11. Cisco-Proprietary
   • 1. Hello Message – Used to elect an Active Router and to let the Standby Router know the Active Router is still available
   • 2. Holdtime Timer – A time after which the Standby Router becomes the Active Router. The Holdtime must be at least three times the Hello interval.
   • 3. Active Router Election – The router (or multilayer switch) with the highest priority is elected as the Active Router. The default priority is 100
   • 4. Tracking Option – Allows an HSRP router to monitor a network condition (e.g. an interface status) and decrement its priority based on that condition
   • 5. Preempt Option – HSRP’s Preempt option allows a router that was previously the Active Router to reclaim its role, if it goes down and comes back up again
   • 6. Default Hello Interval is 3 seconds
   • 7. Default Holddtime is 10 seconds
   • 8. Multicast is 224.0.0.2 (v1) and 224.0.0.102 (v2)
   • 2. HSRP configuration
     • R1(config)#int fa 0/0 R1(config-if)#standby 10(group number) 10.1.1.1 (virtual ip address) R1(config-if)#standby 10 priority 110 (makes router active)
     • R2(config)#int fa 0/0 R2(config-if)#standby 10 10.1.1.1
     • R2(config)#int fa 0/0 R2(config-if)#standby 10 10.1.1.1
     • R1(config)#int fa 0/0 R1(config-router)#standby 10 preempt
     • R1(config)#int fa 0/0 R1(config-if)#standby 10 track serial 1/0 20(decrement value)
   • 3. HSRP Verification
     • R1#show standby
     • R1(config-if)#standby version 2 (faster convergence times) R1(config-if)#standby 10 timers msec(milliseconds) 100 msec 300

2. 2. VRRP

   • 1. VRRP (Virtual Router Redundancy Protocol) – A standards-based First Hop Redundancy Protocol (FHRP)
   • 2. Master Router and Backup Router
   • 3. Preempt Option is enabled by default
   • 4. Default Master Advertisement Interval is 1 sec
   • 5. Use Interface IP Address as virtual IP Address
   • 6. Multicast address of 224.0.0.18
   • VRRP configuration and verification
     • R1(config)#int fa 0/0 R1(config-if)#vrrp 10(group number) 10.1.1.1(default gateway) R1(config-if)#vrrp 10 priority 110
     • R1#show vrrp brief R1#show vrrp

3. 3. GLBP

   • 1. Gateway Load Balancing Protocol (GLBP) – A Cisco-proprietary First Hop Redundancy Protocol (FHRP) that can load balance within a single GLBP group
   • 2. Active Virtual Gateway (AVG) – Responds to ARP requests from hosts and assigns virtual MAC addresses to members of the GLBP group
   • 3. Active Virtual Forwarders (AVF) – A member of a GLBP group that discovers an Active Virtual Gateway (AVG), based on Hello messages, and learns its virtual MAC address from that AVG
   • 4. The AVG router gives a virtual MAC to the PC which corresponds to that router, but if a second PC asks the MAC address of the virtual default gateway it gives a virtual MAC pointing to the AVF or another router. Load balancing and redundancy
   • 5. Redirect Timer – Says how long an AVG will respond to ARP queries with the virtual MAC address of a failed AVF
   • 6. Forwarder Time-Out – Says how long a backup AVF will accept frames destined for the virtual MAC address of a failed AVF
   • GLBP Configuration and verification
     • R1(config)#int fa 0/0 R1(config-if)#glbp 10(group number) ip 10.1.1.1 (virtual IP) R1(config-if)#glbp 10 priority 110 R1(config-if)#glbp 10 preempt R1(config-if)#glbp 10 load-balancing
     • R1#show glbp brief R1#show glbp