Trunking access switches to N9K

[benasitellu]

I have nexus 9200 switches in vPC acting as the core for an office building that’s more traditional campus - pair of catalyst switches per floor, /24 subnet per floor all svis on the nexus switches.

Currently the catalyst switches each have 1 fiber run to each Nexus and spanning tree blocks one of those on the Catalyst side because the vPC looks like one switch. This works fine and will swap to the alternate link if the Nexus side drops.

My question - is it better practice to bundle these links (MLAG on the Nexus / regular lacp ether channel on the Catalyst) to take advantage of both links or I am just adding complexity where it’s not needed? 1G links and I can’t imagine using saturating one, user traffic just isn’t that much.

[MHM Cisco World]

sure connect SW to two NSK vPC via PO is best design
without PO as you mention always one link will be UP other is down backup 

with PO both link is UP and there is Load balance 

MHM

[M02@rt37]

Hello @benasitellu 

In your desired setup with Nexus 9200 switches in vPC acting as the core and Catalyst switches per floor, bundling the links using EtherChannel (MLAG on the Nexus and LACP on the Catalyst) offers several advantages.

It allows you to utilize both links simultaneously, effectively doubling the available bandwidth and providing more headroom for future traffic growth or unexpected bursts. EtherChannel also supports load balancing across multiple links, optimizing network performance by distributing different types of traffic. Additionally, it enhances redundancy since traffic can continue flowing through the remaining links in the event of a link failure, ensuring minimal disruption. 

Given that your current 1G links are sufficient for user traffic and not nearing saturation, and considering the potential added complexity, it may be advisable to stick with your current STP setup for now. This setup provides a stable and reliable network configuration with redundancy through spanning tree, which can swap to the alternate link if needed. However, if you anticipate significant increases in traffic or want to proactively optimize link utilization, implementing EtherChannel could provide performance and redundancy benefits. The decision ultimately depends on balancing the current and anticipated needs of your network with your comfort level in managing the increased complexity. If you have the resources and expertise to handle the additional complexity, bundling the links could be beneficial. Otherwise, maintaining the simpler STP setup remains a robust and effective choice...