We are currently having issues with our primary internet provider keeping the WAN circuit up. We would like to add another internet provider as a backup. We are using a Meraki mx250. How do we set this up so the secondary WAN takes over if the primary goes down?
Just connect the second provider up to WAN2. It will automatically do what you ask, no config required.
You can tweak the settings if you need to under Security & SD-WAN > SD-WAN and traffic shaping.
https://documentation.meraki.com/MX/Firewall_and_Traffic_Shaping/SD-WAN_and_Traffic_Shaping
Yup, sounds like a Layer 1 problem if you have a link flapping. Try swapping the cable and/or the SFP.
Are you using a copper or fibre link?
Does it only flap when connected to the MX? If you connect a laptop directly do you have the same problems? Or can you put a switch in between and it has the same problems?
If you have a supported SFP try that for sure too.
Not saying this is the solution to the issue you are having. But may help others who pass through.
Our backup link would go to sleep. We setup a monitor in WUG to keep it awake.