Single MX to 2 MS connections

[Pwellion]

Very Simple question. Looking for best practice connecting 2 x M130-48x to a single MX250/450 (we only have a single so not doing ha yet)

Internet circuit on a 10Gb bearer capped to 5Gb. MX Will act as layer 3 for a couple of vlans, traffic mostly north south. Is this as simple as connecting each MS to a single 10Gb lan port on MX? would there be any harm in adding another 10G link between each MS which for added redundancy assume Rstp would block the loop.

Also if I swapped to 2 x MS225 In a stack assume if I created 2 x 10Gb uplinks to MX (one from each stack member) then RSTP would block one of uplinks. Trying to find the best balance between redundancy and stability. Any chance MX will ever support linK aggregation?.

Thanks

[alemabrahao]

LACP & Link Aggregation

The MX does not run LACP or any link aggregation protocols. Connecting aggregated ports to the LAN of the MX is not supported; all connected ports should be un-aggregated. If multiple ports are connected to the MX from a single switch for redundancy, it is highly recommended that you run STP on that switch, to ensure that one of the redundant ports is safely put into a blocking state.

https://documentation.meraki.com/MX/Networks_and_Routing/MX_Layer_2_Functionality

[GIdenJoe]

You can easily downlink your MX to two switches downstream.  It will not run LACP or STP at this time however the switches will block links due to the forwarding of BPDU's across the MX.

If you don't use stacking switches right below your MX'es then it is important to choose the correct links to downlink from MX to both switches and to interconnect both switches.
Normally you want your east-west traffic between switches to flow directly from switch A to B and not cross the link towards the MX.  In that case make sure one of those two switches is the STP root and you connect a lower numbered port between the switches than the uplink towards the MX.  So the link on the non-root switch towards the MX will be blocked.

[Brash]

It's very unlikely the MX will support LAG any time soon.

As said above, if you add additional links to the MX STP should block all but one. This technically provides redundancy as if the active link goes down, a blocked link should come online.

Personally, I'm not a fan of trusting my redundancy to STP as if it gets it wrong, L2 loops are really messy to deal with.

[K2_Josh]

For more HA design approaches, please see @KarstenI's excellent article.