How can I setup a layer2 failover configuration?

My Network setup:

The distance between Site A and Site B is 2 km. Both sites are connected via a wireless link. As a backup line, we also have a layer2 fiber link between these two sites.

Primarily I want to transfer all traffic on the wireless link only, and do not use fiber link at all, if the wireless link is working well.

I want to activate the fiber link automatically, but only if the wireless link is down. And when the wireless link is restored, automatically deactivate fiber link port.

Ether-port A (wireless) needs to continuously ping the other side, and if no there is no ping reply, then activate Ether-port B(Fiber), so all traffic routes without any interference.

When Ether-port A(wireless) ping gets a reply, cut off PortB.

If you ask why not to use fiber always when fiber is better then wireless: I my ISP charges per GB for data traffic. So it is expensive when wireless link is running.

  • Unfortunately I don't think this is possible with layer 2 and using two different technologies without doing the switch over manually. If you were to use layer 3, your options would be greater because you could use something like HSRP. If you had to use layer 2 and both links were the same, you could have used LACP or rapid spanning tree to accomplish what you are requesting.
    – SleepyMan
    Nov 1, 2016 at 8:57
  • Would (rapid) spanning tree work for you? The failover time would be a couple of seconds, and the traffic on the fiber link would be minimal.
    – Ron Trunk
    Nov 1, 2016 at 11:59
  • This would be potential for him however he would need to check to make sure his ISP does allow BPDU's across the link?
    – SleepyMan
    Nov 1, 2016 at 13:08
  • @user42016 - It's not that tricky but could you post a diagram of your set up that includes the hardware models. Some set-ups may or may not work based on your current infrastructure.
    – user4565
    Dec 1, 2016 at 21:01
  • I do not have Layer 3 topology. It is about Layer 2. As Ron Trunk said, RSTP is perfect for this layer 2, but also as issue is as'SleepyMan' said above, my ISP does not allow BPDU across the link. So what other option is available?
    – Teknas
    Dec 6, 2016 at 7:39

1 Answer 1


If you have any kind of Layer 3 equipment in that setup, you should be able to easily do this by having both being routes to your destination, with A having a lower metric than B. This would cause all traffic to exit via A, only using B when A is down.

  • Exactly. Put a router on each end. Jan 5, 2017 at 17:02

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