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neo64_66457's avatar
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Dec 30, 2010

Standby - Active HA F5 Pair Best Practice Cabling question?




I currently have a Active Standby pair of F5 LTMs. They each connect to a separate 6509 Cisco switch. Each Cisco switches connect to each other using Etherchannel trunk bundle. However I noticed that when upgrading a HOT FIX and rebooting my standby F5 impacted my production network as both F5s became active.



[f5 a] [f5 b]


| |


| |


[6509 a]---[6509 b]




I am told by F5 that it is better to directly connect the F5s together and have a separate IP subnet for the keepalives to avoid this.



Any recomendations for high availability and to prevent ACTIVE Active from occuring in an Active Standby configuration?



prior to upgrading a hot fix on my standby unit I did verify the following:


( b ha table )






Feature Key Action En? Act Data


network failover nw_heartbeat go active yes no 35963321


network failover peer_unit no action yes no 0







( b mirror show )




No interface mirrors were found







( b db show )




Failover.ForceActive = disable Failover.ForceStandby = disable





1 Reply

  • If the units are close enough (50 feet) to use hardwire failover, that's the best option as it's low level and fast. I generally don't recommend using a trunk for network failover as the config needs to load before the trunk can come up and the trunk needs to be initialized. As the trunk comes up, the unit will be active and cause IP conflicts for shared IP addresses. If you need to use network failover, you can use a single cable between the units (ideally with no switch).



    I don't suggest using a preferred active/standby configuration as this can cause an unnecessary failover when the preferred standby unit is active and the preferred active unit comes back up.



    Here are a few related links:



    sol2397: Comparison of serial failover and network failover features




    Network Failover: