Flexible Stacking - Layer 3 Redundancy or Not?

[AC_Phase9]

Hello all.  I'd like to get some clarification on flexible stacking.  We purchased MS425-16 switches for a distribution switch stack, that would need Layer 3 redundancy.  Before purchasing the switches, I reviewed the flexible stacking documentation, which stated "full redundancy for your gateway".  I am now being told that Flexible Stacking does not support Layer 3 redundancy, and that only physical stacking supports this.  I'm a bit confused as to what "full redundancy for your gateway" means if not layer 2 and layer 3...

From Meraki documentation (https://documentation.meraki.com/MS/Stacking/Switch_Stacks😞

Understanding Flexible Stacking 

Availability and redundancy are most helpful at the distribution layer of a network. On MS420 and MS425 series switches, any two ports can be configured as stack ports. This allows for full redundancy setup for your gateway and minimizes the impact of a failure in the network.

Can someone please confirm whether I would have layer 3 redundancy with Flexible Stacking?  If not, I believe Meraki needs to drastically modify their documentation on this because this is extremely misleading.

[PhilipDAth · Accepted solution]

When answering this I'm going to assume you are using flexible stacking and have it configured as an actual stack in the Meraki dashboard (as opposed to having it as two seperate switches configured as a warm spare using VRRP and just using stacking cables for connectivity).

Flexible stacking DOES provide layer 3 redundancy.  I've used this many times on MS425-16 and have tested it.

Things like IP addresses and static routes move almost instantly from the primary to another stack member on failure.  Dynamic routes like OSPF are not mirrored.  So on a primary switch failure, OSPF is then started on the next stack member to become the master, and you have to wait for OSPF to re-learn the routes.  This might take 5s.

[AC_Phase9]

Philip,

Thanks for clarifying this!  We literally had Meraki support inform us that it does not support Layer 3 redundancy...  You are correct, They are actually stacked and configured as such in Meraki.