I've always stacked switches before, but want to take advantage of the reduced downtime for firmware updates that MLAG allows. I'm following the documentation here: https://downloads.dell.com/manuals/common/powerconnect_nx00-usingmlag-whtppr_en-us.pdf

I'm following from page 16 / heading 5 - "Two-Tier MLAG Example"

I have 4 x N4032F switches I wish to set up in a two-tier configuration (representing 2-5 in the diagram), with 2 x N2048P switches acting as 1 & 6 in the diagram. So far so good. 

The diagram shows MLAG Domain 1 & MLAG Domain 2. 

I notice that for switches 2-5, there are instructions as follows:
vpc domain 1

My hopefully simple question is, should this be vpc domain 2 for switches 4-5? The less simple question might be, if not, why not?

Many thanks!