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Pawan_Goswami's avatar
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Aug 26, 2021

F5 not support cable failover? or how can be configure

As mentioned in picture, If we connect F5 with two different switches using port 1.0 & 2.0.

Both ports having same access vlan and they will be un-tagged with same vlan VLAN12.


Now seems F5 not compatible with cable failover as same selfIP , F5 advertising to switch using interface 1.0 and 2.0.

Which creating switch STP loop and due to STP default behavior, One interface switch put in error disabled state.


Is any way on F5 to support cable failover, incase one cable goes faulty, traffic will sent to switch 02 switch another cable. seems F5 incompatible here and TAC guys don't have answer.

3 Replies

  • Hi Pawan,


    In your topology you should activate spanning-tree in the F5 box and play with priorities so that one of the F5 interfaces is always the one that's going to be blocking.


    Note, however, that F5 does not support per-vlan spanning-tree - like Cisco switches use by default. Be careful with that.


    If your switches are totally separate, I'd recommend trying MSTP. Most switch vendors support it and it's the only way to make everything 100% compatible.


    If your switches are physically separate but support some sort of virtual multi-chassis link aggregation (Cisco VPC, Aruba VSF, etc.), or if they form a stack, you'd be better off using LACP. You'd eliminate loops and avoid spanning-tree issues.



  • Thanks for your suggestion but in my environment, Switch are different platform at all and can't support link aggregation/fex extender like (Cisco VPC, Aruba, Cisco 650X VSS or Stacks switches..). Also I am looking cable failover scenarios not vlan failover.


    I tried to put one interface on F5 as passive and another as forwarding. But seems i2600 F5 platform not supporting that feature enablement and it's look like F5 completely in-compatible with link failover.

  • Ok, when you say "cable failover" in F5 it does not mean what you think it does. The "failover cable" has DB9 connectors and only legacy platforms use it. Recent models support only network failover. See for details.


    [EDIT: Correction: newer systems also support "cable failover", but it's a special RJ45 cable. Anyway it does not affect what I'm saying next.]


    For your scenario, I believe the way to go is with MSTP. See:


    Look into your switch vendors' documentation on MSTP as well.