but that's NOT why Cisco is valuable. Cisco is dominant because of network effects
This is the first time I see anyone arguing that market domination by brand X (in any market) is good because of the network effect.
There are lots of people who know the Cisco ios CLI, and the intricacies of their specific product lines.
Ditto here. The dominance of brand X is good because its products are so idiosyncratic that you need a lot of people to use it so that you could have a pool of people from which you could hire someone to manage it. I'm not sure what particular logical fallacy this is but I'm sure there is one.