Building a big data center and looking for a switch to match? How do 256 10 Gigabit Ethernet ports and nearly 1.7 terabits of capacity sound?

That's what Cisco is offering with its brand new Nexus 7000 Series data center switches. Intending these boxes to be a data-center mainstay for the next decade, Cisco has constructed the Nexus switches to be far larger than its current high-end offerings.

Indeed, this exclusive test was the biggest we've ever conducted. Cisco's engineers told us they too had never before tested at this scale. Besides performance, we also assessed the Nexus in terms of features, usability and high availability and resiliency.

Performance turned out to be only fair, in part because current line cards tap just a fraction of the switch's 1.691Tbps capacity. Resiliency, useful features and a modular design are what really make the Nexus switch an interesting contender in data-center switching.

The layered look

While modularity has long been a part of chassis-based switches, the Nexus extends this approach with a layered, redundant approach in both hardware and software. The switch uses a mid-plane design with up to five 230Gbps fabric cards and, in the Nexus 7010 version we tested, up to eight line cards and two management cards. A larger 7018 chassis, due to ship by year's end, will support up to 16 line cards and up to 512 10G Ethernet ports. Significantly targeted for data-center use, Nexus switches also support Fibre Channel over Ethernet (FCoE) cards, but we did not test these.

The management cards are beefier than those on current high-end Catalyst 6500s, featuring dual-core Xeon processors and 4GB of memory. A new operating system, dubbed NX OS, takes advantage of the extra horsepower, as do the system's larger routing tables and virtualization features.

On the software side, NX OS's modular design differs from Cisco's venerable and monolithic IOS. With the Linux-based NX OS, each layer-2 and layer-3 protocol runs as a separate process. If there's a problem with one process, it won't affect other parts of the system -- something our test results demonstrated. The switch still supports the familiar IOS command-line interface (CLI), but it too is just another process.

In many ways, the Nexus CLI is a better IOS than IOS. Longtime Cisco users will appreciate that NX OS finally supports IPv4 addressing using classless inter-domain routing (CIDR) notation, saving many keystrokes. NX OS also allows inline configuration editing with the Unix sed (stream editor) command. The sed command enables search-and-replace editing of a configuration file from the command line, a great timesaver.

Another useful improvement is the inclusion of a packet capture and decode facility. The CLI has commands to read traffic headed to and from the management cards, a helpful tool in troubleshooting. There's a tcpdump-like decoder available from the command line, or, additionally, users can save captures for decoding by Wireshark.

NX OS also supports virtualization through the use of virtual device contexts (VDC), allowing up to four complete virtual switches to be defined on a single platform. As with process separation, the VDCs operate independently of one another.