FHRP

FHRP

1. GLBP

   • Cisco Proprietary Hello is 3 seconds Load Balancing 224.0.0.102 UDP 3222 (src and dst)) AVF (Active Virtual Forwarder) AVG (Active Virtual Gateway) State is Listen/Active Simple text password Preemption is disabled by default
   • AVF
     • Each one is assigned a Virtual MAC Address Assigns virtual MAC address 0007.b4 up to 4 virtual forwarders per group. forwarder preemption uses weighting instead of priority and is enabled by default.
   • AVG
     • glbp preempt - Not ON by default Send ARP replies Members of a GLBP group elect one gateway to be the active virtual gateway (AVG) for that group. Assigns virtual MAC address 0007.b4
     • Load Balancing
       • Not enabled by default glbp xxx load-balancing ? none host-dependent round-robin weighted Do the above on all routers glbp xxx weighting y Base on the ARP replies
       • Tips
         • Weight can be adjusted based on object tracking
       • Configuration
         • int giga glbp X ip address show glbp State Listen/Active

2. VRRPv2

   • Standard base protocol RFC 3768 Master/Backup protocol 112 (own protocol) 224.0.0.18 - IP 0000.5E00.01XX Preemptive by default Higher IP address win by default Hellos are only sent by the Master router
   • Configuration
     • int giga X vrrp group number IP
     • Tips
       • Sends gratuitious ARPs when it becomes the Master You can kill it filtering IP 112 224.0.0.18 (Switch generates mac flap notification) because two routers are claiming to have the same virtual IP address

3. HSRPv1

   • HSRPv1 by default Cisco Proprietary State = Standby or Active Hello time = 3 (default) Hold time = 10 (default) 100 default Highest Ip address (Tie Breaker) Non Preemptive UDP Multicast 224.0.0.2 port 1985 Clear text or MD5 (by default it's clear text and the password is cisco) MAC 0000.0c07.acXX XX = Group Number in Hexadecimal HSRPv2 allows more groups HSRPv2 uses 224.0.0.102 when you have three routers the third one will be on the listen state
   • Configuration
     • interface X standby  1 standby version 2 standby 1 priority X standby preempt show standby (brief|all)
     • Tips
       • Telnet to the virtual IP address and see where it lands. Nexus supports Active/Active Preempt must be configured on both sides if you have a dual exit

4. Track

   • ip sla 1 icmp-echo 1.2.3.4 frequency 3 timeout 1000 threshold 100 ! ip sla 1 schedule 1 start-time now life forever track 2 ip sla 1 int gigaX standby 1 track 2 decrement 20

5. IPv6

   • HSRPv2
     • Enabled with standby version 2 224.0.0.102 Increases group range Advertises both IPv4 and IPv6 gateways
     • Configuration
       • standby version 2 standby 1 ipv6  fe80::1 show standby On the "host" (router) ipv6 address autoconfig default clear ipv6 neighbors
   • VRRPv3
     • RFC5798 enabled with fhrp version vrrp 3 Advertises both IPv4 and IPv6 gateways virtual IP address must be a link local address
     • Configuration
       • Turn it on globally first: fhrp version vrrp v3 ! int giga X vrrp 1 address-family ipv6 address fe80::1 primary ! show vrrp
       • Tips
         • Can't run previous version and the new one at the same time
   • RA
     • You can have the same behavior accomplished by FHRP using RA on IPv6 (Route Advertisment)