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Road to CCNP: Day 105

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kbmarco

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3.3.c Configure first hop redundancy protocols, such as HSRP, VRRP

FHRP use Virtual Ips (VIPs)

  • Hot Standby Router Protocol (HSRP, one VIP, two routers, failover), active standby
  • Virtual Router Redundancy protocol (VRRP, one VIP, two routers, constant probing of other router, failover when other router fails to respond in time), master backup
    • HSRP is cisco proprietary, VRRP is open
  • Gateway Load balancing protocol (GLBP, multiple routers, traffic can be round-robined to different routers, or statically assign a flow to a specific router)

HSRP Config

1. Define instance with standby [instance-id] ip [virtual IP address of gateway]
2. (optional) enable preemption with standby [instance-id] preempt
3. (optional) change default priority with standby [instance-id] priority [priority #]
4. (optional) change HSRP mac address in case of network migrations with standby [instance-id] mac-address [mac address]
5. (optional) change the HSRP timer with standby [instance-id] timers [seconds | miliseconds]
6. (optional) enable HSRP authentication with standby [instance-id] authentication [text password]
7. View HSRP status with show standby [instance-id] [brief]

Why object tracking is needed: it’s needed because of R1 doesn’t actually go down but its link does, object tracking can detect the link down state and decrease R1’s priority so that R2 can preempt it

Track [object #] interface [interface #] OR track [object#] ip route [route/prefix] reachability
Standby [instance-id] track [object-id] decrement [decrement value]

Virtual Router Redundancy Protocol (VRRP)

  • Uses master/backup instead of active/standby
  • Preemption enabled by default
  • Commands start with vrrp instead of standby
  • Mac address structure 0000.5e00.01xx where xx is VRRP group ID in hex (remember openstandard = advanced, 5e)
  • Uses 224.0.0.18 for communication
  • VRRPv2 is Ipv4 only, VRRPv3 supports IPv4 and IPv6
1. vrrp [instance id] ip [VIP address]
2. (optional) change priority with vrrp [instance-id] priority [priority #] 1-255
3. (optional) enable object tracking to change priority when object is down vrrp [instance-id] track [object-id] decrement [decrement value]
4. (optional) enable VRRP authentication with vrrp [instance-id] authentication [password]

Hierarchical VRRP in VRRPv3

Like an ACL, you create the instance and then issue commands in the config modeo f that instance

1. Enable VRRPv3 with fhrp version vrrp v3
2. Define the instance with vrrp [instance-id] address-family [Ipv4 | Ipv6]
3. (optional) enable compatibility with command vrrpv2
4. In config mode, define the gateway VIP with command address [ip-address]
5. (optional) change priority with command priority [priority #]
6. (optional) enable object tracking with command track [object-id] decrement [decrement-value]

Gateway Load Balancing Protocol (GLBP) = provides the redundancy of HSRPs and a load-balancing capability

so basically different hosts use the same VIP for gateway, get assigned different routers by the AVG, and use different MAC addresses for the ARP mapping of their default gateway

1. Define GLBP instance with command glbp [instance-id] ip [VIP address]
2. (optional) configure preemption on the preferred router with command glbp [instance-id] preempt
3. (optional) change priority with command glbp [instance-id] priority [#] 1-255
4. (optional) change timers with command glbp [instance-id] timers [hello seconds] [hold seconds]
5. (optional) enable authentication with command glbp [instance-id] authentication [password]

GLBP weighting types

  • Round robin
  • Weighted = assign weights to each device to define the ratio of load balancing
  • Host dependent = map a HOST MAC address to a virtual forwarder MAC

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