Equinix has declared itself a customer for Cisco‘s Application-Centric Infrastructure (ACI). But that doesn’t mean the company is betting on Cisco’s version of SDN to take over the world.

Equinix announced today that it’s using ACI to connect the Equinix Cloud Exchange to Intercloud, Cisco’s design for creating a network of clouds. The partnership is among a flurry of announcements that Cisco made around Intercloud today.

It’s not that Equinix wants ACI to be the only option for connecting to the Equinix Cloud Exchange. “We want to enable all the key players. If someone wants to use VMware, we’ll let them,” says Ihab Tarazi, Equinix’s chief technology officer.

It’s more that some Equinix customers are already on the way toward using ACI, so if Equinix uses ACI too, that opens some interesting possibilities. “They don’t have that ability to extend that ACI control to our Cloud Exchange. This will allow them to do that,” Tarazi says.

As Tarazi explains in a blog posting published today, customers would provide Cisco’s gear with policy and service-level agreement (SLA) information. Cisco, through ACI, would then send the appropriate commands to clouds, with Equinix providing the necessary interconnection.

Customers “would be able to use ACI to control our infrastructure. That’s how we’re thinking about it,” Tarazi says.

Here’s another way to look at it. The Cloud Exchange has its own service provisioning layer that uses tools including software from Tail-f, a network configuration startup that Cisco recently acquired. ACI would add a higher level of control, coming from the policy layer. (That stuff involves declarative networking and policy-based control — for more, see here.)

So, Equinix will be going whole-hog with ACI. In the past, Cisco has counted customers as using “ACI” if they just deployed the Nexus 9000 switches, which can be run in a non-SDN mode that’s no different from yesterday’s networks. Equinix isn’t one of those cases; inside Cloud Exchange, the company will deploy Nexus 9000s and the Application Policy Infrastructure Controller (APIC), the key piece that turns ACI into an “SDN” deployment.

The Equinix Cloud Exchange  uses about 100 data centers to house workloads and networking gear for about 1,200 cloud and IT services providers. The idea is to give enterprises connectivity between clouds, letting workloads and data interact across cloud boundaries.

Cloud Exchange sounds a little like Intercloud, but there’s a difference in scope. Equinix’s business is the connecting of carriers to each other, often on a big geographic scale. Cisco comes from the enterprise, so while Intercloud is about connecting clouds, its mechanics have more to do with tinkering at the virtual-machine level, Tarazi says.