VMware’s NSX now has 100 paying customers, with more lining up thanks to free publicity from last month's Cisco Live conference, according to VMware CEO Pat Gelsinger.

He was speaking yesterday at the Bank of America/Merrill Lynch Global Technology Conference in San Francisco in an hour-long moderated session where he got to talk about VMware's overall business.

One hundred customers is a vast improvement over the handful VMware normally cites — particularly, the five customers Nicira had upon being acquired in 2012, a group that includes eBay, and Rackspace.

Vendors can often find ways to stretch the number of customers or deployments that a product has, so it's not clear how seriously those 100 are using NSX. Gelsinger did acknowledge that the 100 are in varying degrees of NSXness. "Some are in prototypes, some are in full deployment, but they're paying customers," he said, and he did note that Rackspace and eBay being "at dramatic production scale."

The most common use case for NSX? Security, in what Gelsinger called microsegmentation: overlays that are secured from other traffic on the network. It's "a fundamentally different way to attack network security that wasn't possible before," he claimed, adding that it puts NSX into "the security budget, which is the fastest growing budget in IT."

Gelsinger's comments are VMware's first public reaction to the barrage of competitive rhetoric that came out of Cisco Live. In keynotes and in media interviews, Cisco officials were quick to declare why the Application-Centric Infrastructure (ACI) is so much better than NSX.

NSX is the logical rival to pick on. Most people I talk to see VMware and Cisco as the frontrunners in SDN, based on the companies' dominant market positions in data centers and enterprises. And Cisco has been asked about NSX repeatedly since VMware launched the product in August.

But VMware and some other competitors were amused to see Cisco pull out the NSX comparisons without prompting. Gelsinger chose to interpret that as tacit acknowledgement that VMware — a Cisco partner, in other circles — is a competitor strong enough to need calling out.

"Cisco declared us public enemy No. 1, so all of a sudden every customer, every purchasing agent, has to say, 'What's going on over there?' We love it. It's just brought us into so many conversations," Gelsinger said.

Among Cisco's strongest criticisms is that NSX requires a network that's managed separately from the existing network. "Your opex will shoot up like crazy. You're managing two separate environments," said Soni Jiandani, Cisco senior vice president of marketing, during an interview at Cisco Live.

ACI might require new hardware (earliest deployments will need the Nexus 9000) and can represent a radically different network, but the result is one network that encompasses old and new gear, Cisco argues.

VMware's counterarguments could include the fact that NSX has been generally available since October whereas fully deployable ACI is still en route (the crucial Application Policy Infrastructure Controller (APIC) is due to arrive "this summer," Cisco now says, a possible modification to the original June schedule). And while Cisco swears ACI will be massively open, it's going to work first on the Nexus 9000 switches, which represent a new investment for customers.

Despite all this, Gelsinger thinks VMware and Cisco can still be friends. "I don't need Cisco to lose, because network virtualization is this overlay that works great on Cisco environments," he said.

You can hear a recording of Gelsinger's BofA session on VMware's web site.

(Photo: Gelsinger at VMworld in August.)