StackWise Virtual in the ACCESS LAYER

[Ex-Engineer1968]

I have a client who is considering configuring StackWise Virtual (SWV) on his Catalyst 9410 ACCESS LAYER switches. The switches have DUAL SUP modules in them and they are L2-ONLY... VLANs, STP, DOT1Q trunk, QoS for VoIP, etc... no routing, no VRFs, etc. Nothing crazy.

According to this white paper on SWV (go under the Topology section), SVW is recommended ONLY for the aggregation and core/collapsed layers. The reason I think is that all the L2 and L3 complexity can be found in those layer, NOT The access layer. So that's where the benefit would be.  \Is that he reason?

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9400/software/release/17-8/configuration_guide/ha/b_178_ha_9400_cg/configuring_cisco_stackwise_virtual.html#concept_al2_ryx_31b

I guess one can argue that configuring SWV in the ACCESS LAYER does simplify management by creating a single virtual switch, so it CAN make sense n the access layer, but really now... we are talking about 2 switches that would hardly be touched after they are deployed. Is the added cost of a DNA Advantage license really worth that? 

Also, let me add this... they bought DUAL SUPs for each 9410 ACCESS LAYER chassis switches because they want redundancy in the chassis since each endpoint will only be singe homed, so they cant afford to have a switch with a single SUP go down and then have to have manual intervention to get the endpoints back up. 

[M02@rt37 · Accepted solution]

Hello @Ex-Engineer1968 

In an L2-only access layer, with dual SUPs already providing redundancy, the benefit of StackWise Virtual may not outweigh the cost of the DNA Advantage license. SWV is most beneficial in layers where you have more complex L2/L3 configurations and require simplified management and redundancy across multiple switches. For your client’s access layer, where the switches are not expected to be touched much post-deployment, SWV might not be necessary.

[Ex-Engineer1968 · Accepted solution]

That's exactly what i am thinking. SWV also doesn't even support a dual SUP set up. If you have two chassis that you want to do SWV on, you must have no more than 1 SUP in each chassis. This customer has 2. It's nearly completely pointless on the L2 access layer. 

This was a fantastic answer because it was complete and addressed exactly what i was asking. Thank you! Are you with Cisco TAC? Just curious. I will eventually accept your answer as the solution, but I just want to see if anyone else wants to chime in first. 

[Joseph W. Doherty · Accepted solution]

One major recommendation for SWV everything should be dual homed.  That's both to provide redundancy and double the bandwidth.  Assuming most edge devices will not be dual home, you lose those advantages.

As you note, you'll only have one logical device to manage, but for an access edge, I would suggest it's a bad trade.

[MHM Cisco World]

SW support dual SUP

I will share later doc very good for this case

MHM