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merikatori_9296's avatar
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Nov 01, 2011

Question about HA active/standby with hard-wired failover

Hi all!



I am going to deploy F5 Big IP systems including two 3900 LTMs (v10) in real world. Everything is fine with LTM VE on VMware when using active/standby with network failover method and VLAN fail-safe. I have read a statement about combining network failover and hard-wired failover: (tmos management guide 10.1)




You use network failover in addition to hard-wired failover. Even with


serial cable failover configured, communication through network failover


is required for certain features to function properly, for example, the


communication that occurs over the network during failover mirroring.





I have three questions about active/standby


1. Which type of communication does the statement indicate?




2. In the case of active unit's VLAN down, if using VLAN fail-safe how does standby unit know to failover to active? through communication of network failover pair or hard-wired failover or configsync ?


(There are three areas to specify three pairs address: network failover, network mirroring, configsync.)




3. Are there any messages exchanged on serial cable or just voltage?




In conclusion, With active/standby, beside to use hard-wired failover with VLAN fail-safe and network mirroring, is it necessary to enable network failover? does it work without defining network failover address pair?




Thanks and Best Regards


2 Replies

  • nathe's avatar
    Icon for Cirrocumulus rankCirrocumulus



    3 - serial cable failover just detects voltage and any loss of voltage will cause a failover.


    2 - it's the active appliance that makes the decision - one of it's deamons will be monitoring VLAN failsafe and will cause the appliance to reboot, restart, failover etc. See System, HA, Fail-Safe, System for a list of which daemons cause which action.


    1 - does it mean connection mirroring? I didn't think this went over the HA network failover interface.



    If you've got hardware failover (f5's recommended failover of choice) then network failure is pretty redundant. It would still require hardware failure too to trigger the Active going to Standby (and vice versa).



    Hope this helps,


  • Hi Nathan!



    Thank you for your reply



    2. Well, local active unit detect VLAN failure by VLAN fail-safe causes the appliance to failover to stand by but HOW standby unit know to failover to active if there is only serial cable just detect voltage? I mean that old active unit must tell old standby unit that "now I become to new standby, you can go to new active unit".How does it do that? I think VLAN fail-safe operates locally on an unit. In order to trigger failover, two units have to communicate with each other.



    1. I think not only network mirroring



    The above statement indicates that Even with serial cable failover configured, communication through network failover is required for certain features to function properly, . Is network failover only used to redundant for serial cable?




    Any ideas everybody?