@#danW wrote: but what I don`t understand is the statement: this can be done as long as the two stacks are both running the same software version.
what does this mean in the case of a software change/update on one of the two stacks, for a certain time the software would here for sure be different?!
I think there is a tolerance: Switches pair must run the same branch software version (e.g. for two 5400R zl2 let we say KB.16.08), they could continue to be part of a DT if their respective running versions stay strictly within that branch version (so any build within the branch 16.08).
Probably the worst case scenario is when a Switch (or an entire Stack as per your scenario) belonging to the DT pair is going to be upgraded to a newer branch version (e.g. from 16.08 to 16.09).
@#danW wrote: Furthermore, I have added another graphic in which in addition to the server, aswitch stack (Model = 2930M) is connected as well on the two DT's! Would it be correct that the configuration on the server and on the switch-stack side would "only" be a normal LAG? Or is there anything about DT that I´ve to think about on that devices as well?
Correct, peers see the DT pair as a single entity so normal LACP Port Trunks are enough to serve uplinks to DT pair.
Instead of using just a 2 links LACP LAG on Server, a 4 links LACP LAG would be better deployed between it and the DT pair...the same could be said for Stack-C but - having a two members stack - it implies you should setup a 8 links LACP LAG from it to the DT pair (that's to cover any possible path and avoid any possible physical link/DT Switch failure combination).
@#danW wrote: in general, how is your personal expirence or opinion about the theme DISTRIBUTED TRUNKINGRegarding: So when they are stacked together, you can just use aggregation (LAG) which is much simpler than using Distributed Trunking.
I think that, with that statement, @Matthew_Fern wanted to point out that setting up (and mantaining) a DT pair to serve peers is more complex than having a backplane stack serving the very same peers, in both cases peers use LACP LAGs...but at DT level the setup is more complex (a Stack would be simpler because there is no dt-lacp but just lacp to setup peer facing).