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Failover between two WAN Links

I have two sites that are several miles apart. They have a fiber (VLAN12) connection between them on the Layer 3 switches and a Microwave (VLAN11) shot between one layer 2 switch and the layer 3. One location is the access to the internet. Is there a way to make a failover through the Microwave if the fiber goes out.





Joseph W. Doherty
Hall of Fame Expert

Yes (probably).

Right now, you don't logically have a L2 link using the microwave path, correct?

You make the microwave path a new VLAN, and then route across it.  (You'll need to extend this new VLAN to both L3 switches.)

Assuming the microwave path is "slower" than the fiber path, you'll also likely want to "cost" it worse than the fiber link, so it will only carry live traffic is the fiber path fails.

The Microwave path has its own VLAN already. I've never done anything like this with Cisco. Is there an example somewhere I can look at for configs?

On the layer-3 switch ( one static route pointing to the layer-3 switch using the fiber link (vlan12) and another static route pointing to the same layer-3 switch (vlan11) with a higher AD. This way, when the primary link (fiber) fails, the traffic should get routed to the microwave.


BTW, did you revise the diagram from your original post?

What you need to do is to have a VLAN11 extended to the router ( on the right.  I.e. both VLANs 11 and 12 need to connect to both routers.

Assuming there's also a VLAN for the 10.2.x.x network, you'll either need an access port on the switch to connect to a different port on the router, or you'll need to change the right router's ( <> switch link to a trunk and configure the router physical port with subinterfaces.

Whether you use a different port on router and switch or subinterface, the router will need an interface in VLAN 11, e.g. perhaps

Once the second VLAN, VLAN 11, connects both routers, you'll have dual paths.  Then you just route between them, as desired.  This might be done using static routes, as suggested by Reza, or you can use a routing protocol.

Since you'll have two L3 paths, it's up to you to decide whether to make one primary and the other secondary, or use them both (normally equally).

If this is unclear, please ask further.

As for examples, much depends on how you're actually configured now, and how you want to use both links.


Yes I updated the diagram. Thought it might help to understand a little more of what the network was like. I will try your suggestion.