The IT network industry is in the midst of revolutionary change. Traditional hardware companies including Cisco, Juniper, and Arista are embracing some form of Software-Defined Networking (SDN). All three companies are looking to deliver and manage networks in drastically different models.

This major change has come about because of the competition from software companies trying to disrupt the network industry by abstracting the network via network overlays, which are commonly referred to as network virtualization. A great deal of FUD has resulted from the disruption of the traditional network model.

Software is pushing network innovation

As solutions from software companies such as VMware and Nuage Networks gain momentum, so has the rhetoric within the overall industry. I addressed the early debates between Cisco and VMware in a post closer to the release of VMware’s NSX. More recently there has been concern over Cisco’s support of VMware NSX.

I recently spoke to a customer of VCE (the converged infrastructure provider formed by VMware, Cisco, and EMC), and he echoed a concern I’m hearing more and more about the support of software-based network overlays on Cisco’s infrastructure. There is a significant difference between support and integration. Cisco does support NSX, but integration is what customers want in the underlay and overlay.

Data center fabrics are still critical

For a practical network virtualization enterprise solution, a data center fabric is required. Data center fabric reduces the operational complexity of traditional networks while increasing reliability. SDN solutions enable nimble network implementation on top of this fabric. Customers want the nimbleness of SDN with the operational functionality of the fabric. For example, the ability to correlate network activity on the overlay and underlay is a critical requirement of a successful SDN deployment. Logic would dictate that, the deeper the integration between the underlay and the overlay, the higher the likelihood for a successful deployment.

The lack of integration is where I’m seeing the greatest level of concern. Companies such as Nuage have decided to take a dual approach of using open standards to work with different vendor solutions while also manufacturing network equipment.

VMware is a software-only company and has decided to use APIs to work with existing hardware vendors. Cisco is an exception to the long list of network vendors announcing deep integration with network virtualization solutions.

Cisco has a competing vision for SDN — the company believes its customers are better served by embracing its Application Centric Infrastructure, which has deep hardware and software integration. Cisco has a fundamentally different view of the integration of software-based network overlays.

Cisco integration with SDN

Cisco states that the company supports NSX as it would any other network application or third-party controller. Based on this statement, supporting NSX should be no different than supporting SAP. The job of the data center fabric is to effectively and reliably move packets; it makes no difference to the underlay if these packets are tunneling other network traffic.

Cisco does offer support for open standards such as OpenFlow, VXLAN, and VTEP, which are used to direct network flows and extend the network overlays to physical ports. However, there are no special hooks or APIs for NSX specifically.

Arista is an example of a network company that integrates with NSX. For example, Arista switches can directly register to an NSX Network Controller and share topology between virtual Open vSwitches on the same controller. Cisco doesn’t allow this direct integration. Open solutions such as OpenFlow or OpenDaylight are used to either control flows between virtual and physical switches or manage the controllers in the case of OpenDaylight.


While Cisco does support NSX from a pure transport and open standard perspective, it is clear that Cisco views software overlays as a suboptimal approach to SDN. If you’re a Cisco customer looking to deploy NSX or any other overlay, you should discuss your concerns with your vendor.

As the lines between the virtual and physical networks continue the blur, the greater the need for integration between the overlay and the underlay. It’s critical to address these integration topics with your vendors.

Disclaimer: As part of my current job search I may speak to one or more of the vendors mentioned in this article about potential employment.