Spine and Leaf Architecture

This topic is to discuss the following lesson:

Hi Rene, excellent post. I have a question regarding vPC on your Conclusions, “vPC somehow solves this limitation of STP, but vPC can only use two active links.” - what do you mean by “only use two active links”?

Hello Laura

When configuring vPC peers, you can only connect to two devices. Specifically, Cisco states:

You can have only two devices as vPC peers; each device can serve as a vPC peer to only one other vPC peer. The vPC peer devices can also have non-vPC links to other devices.

Note some invalid configurations below:
image
You can find out more info at this Cisco documentation:

So vPC provides redundancy in pairs, and does not even come close to the level of redundancy made available by the spine and leaf architecture.

I hope this has been helpful!

Laz

Hi guys
I think you don’t get Laura’s point- you can only connect 1 switch to 2 vpc peers , but that does not mean you only can have 1 uplink to each peer.
We have in our datacenter configured some switches with 8 uplinks to each 5k nexus, so you have 8 links participating in 1 vpc
The picture you showed is for 1 switch connecting to 3 vpc peers - that is not possible, but 1 device connected to 2 vpc peers using 8 links on switch and 4 on each vpc peer is doable and frequently used

Hello Marek

Yes, thanks for the clarification. It is true that you can have each individual uplink to a peer be composed of an etherchannel, so that you can have up to 8 physical links to each of the vPC peers. That way you can have up to 16 physical links.

However, the limitation that Rene was speaking about in the lesson is the fact that you are limited to uplinks to a maximum of two vPC peers. You cannot have uplinks to more than two physical switches like you can with spine and leaf.

I hope this has been helpful!

Laz