We keep hearing a rumor that VMware is on the verge of acquiring Cumulus Networks. It’s a compelling theory, but some sources around the industry say VMware has a lot of reasons for not doing it.

What makes the rumor fun is that VMware’s NSX and Cumulus’ Linux OS for white-box switches both carry the seeds of networking revolution. Cumulus is a software vendor, but it does have customers who want the startup to provide fully loaded switches — which means an acquisition could essentially pit VMware against Cisco. Grab the popcorn.

NSX needs switches — a network upon which to build its network overlays. VMware has satisfied that need through partnerships with hardware vendors and with Cumulus. It’s enticing to think of the company bringing part of that capability in-house.

One rumor earlier this year even said Cumulus (whose mascot is a rocket turtle, in case you’re wondering what that picture above is all about) had interrupted the process of hiring more salespeople, presumably because they’d be redundant after an acquisition.

What’s not to like?

First, Cumulus isn’t seeking the credibility of a big-name partner; it’s already got Dell. (Dell has also announced a partnership with Big Switch Networks, part of a campaign to apply these off-the-shelf software packages to non-white-box switches.)

Cumulus might also be a more complicated integration than Nicira was. VMware is a software company. Cumulus, which makes its Cumulus Linux available as open-source code, sells services and support, a business more closely aligned with those of Red Hat or Canonical (curators of the Ubuntu Linux distribution).

But maybe the biggest obstacle is the fact that Cumulus just doesn’t need to get acquired. The company is still at an early stage, with a hot name and a lot of potential. Moreover, startups are going for a lot now. Facebook‘s $19 billion acquisition of WhatsApp is from an entirely different industry, but it sets a tone for tech deals. VMware bought Nicira for $1.26 billion. If you were Cumulus, how many billions would you ask for?

Despite the arguments against the deal, the VMware-Cumulus rumor isn’t going away. If they actually get together, there’ll be a lot to talk about.