For example Cisco and Dell check these DAC (a.k.a Twinax) cables to be from Cisco resp. Dell, thus you cannot interconnect switches from those vendors with a DAC.
Other vendors, like Arista, do not check DACs, only SFP+ modules, to be branded correctly. This allows the use of any DAC cable (as long as it works, of course), even to connect to e.g. Cisco or Dell.
Extreme EXOS and EOS do not impose specific branding for either DAC of SFP+, 3rd party is fine if it works, but use of non-Extreme optics is not covered by Extreme support. Thus Extreme switches can even be connected to other vendor's switches using a DAC.
