HA MX Configuration without redundant connections

[Layer8Problem]

Hello, 

We want to migrate all of our VM workload from the current DC to a COLO which is connected by dark fiber. 

I am concerned about what might happen if our dark fiber connection between the two locations gets cut. 

Here is our current setup:

I looked into the MX warm spare documentation and found this recommendation:

However I'm wondering if it's still possible to configure HA without the cross connections in the middle of this diagram. 

Fairly new to Meraki, thanks in advance for the help.

[Ryan_Miles]

These MX84s are a HA pair? If yes they need to have an active LAN connection(s) for VRRP heartbeats as the doc diagram shows.

If your diagram is representing a MX HA pair and the dark fiber link went away there'd be no HA LAN link remaining and both MXs would assume they're the primary unit. https://documentation.meraki.com/MX/Deployment_Guides/MX_Warm_Spare_-_High_Availability_Pair#Dual_Ac...

[Layer8Problem]

They are not currently set up as HA pair, each MX is set on it's own network. 

I'm mainly concerned with being able to connect with our COLO environment in the event of a cut to the dark fiber. 

Could I load or copy the configs of the DC MX onto the unused one and use it as a backup? 

I've been warned not to just plug in the unused MX into the network to see what options I have.

[alemabrahao · Accepted solution]

Yes, you can, It will work as expected.

[PhilipDAth]

With regard to your dark fibre - you will have issues if this single link goes down.  Both MXs will become master.

I would recommend using a pair of links for redundancy and forming them into a LACP channel to make them look like a single link again.