Cisco has had a testy relationship with its longtime partner VMware in the battle for software-defined networking customers, but chief executive Chuck Robbins suggested last week that this may be changing.

As CRN USA reported last month, several joint customers have begun deploying Cisco's and VMware's SDN technologies side by side to solve specific business challenges. On VMware's earnings call in April, the virtualisation vendor's chief executive, Pat Gelsinger, said SugarCreek and Shutterfly were examples of customers that are using both versions of SDN.

Asked whether Cisco and VMware might consider working together to make it easier for customers to use the two technologies in tandem, Robbins said the vendors are actively exploring such an arrangement.

"As it relates to VMware, I think our teams are talking about where there might be points that balance the competitive nature of the partnership, but also meet perhaps some of the emerging customer asks. So I think it that's to be determined," Robbins told CRN USA.

In the interview, Robbins compared the SDN situation with VMware to Cisco's longstanding competition with Microsoft in the unified communications space.

"Our customers have wanted us to drive greater interoperability in our collaboration portfolios, and I think that's something both of us should consider and we're having conversations about it," Robbins said of Microsoft.

Cisco's SDN offering, called Application Centric Infrastructure (ACI), is a software-hardware mix that includes Nexus 9000 switches and its Application Policy Infrastructure Controller (APIC). VMware's offering, called NSX, is a software-only technology.

While Robbins has also criticised NSX as being unfit for enterprises, the Cisco-VMware relationship has seen a noticeable thaw since he took the helm last July, according to several partners that work with both vendors.

Ross Brown, VMware's senior vice president of worldwide partners and alliances, told CRN USA that his company has always been open to working with Cisco and other networking vendors on SDN integration.

"VMware has maintained for some time now that NSX and ACI are not competitive, and even partners and customers are proving this out in the market today," Brown said in an email. "Since introducing NSX, we have welcomed the opportunity to partner with all of the major networking hardware vendors."

Most industry watchers believe there is plenty of room for both Cisco and VMware to thrive in the SDN market, and both are seeing strong growth for their respective SDN offerings.

Cisco, in its third quarter earnings Wednesday, said ACI revenue grew 100 percent year over year and is now on a US$2.2 billion annualised run rate. VMware said NSX licence bookings grew 100 percent year over year last quarter, but the vendor hasn't updated the US$600 million run rate figure for NSX it announced in January.

This article originally appeared at crn.com