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Ethan Banks
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Arista 7500E Switch Puts Up Big, Big Numbers

Arista Networks’ 7500E makes switches exciting again. New line cards support 10, 40 and 100GbE mix-and-match ports and offer outstanding port density. Arista’s per-port pricing is also compelling.

Network switches typically aren't all that interesting. Necessary? Yes. Functional? Clearly. Exciting? Not so much. But once in a while, a network switch comes along that gets network engineers' blood flowing. The Arista 7500E is just such a switch.

The Arista 7500 is a chassis that's been around for a few years now. The 7500E is not a replacement chassis; rather, the product line denotes a group of new line cards and fabric modules that take the existing 7500 chassis to higher levels of performance. Current 7500 customers will not replace either the chassis or the power supplies to use the new 7500E series products.

The four new 7500E line cards are as follows:

A 12x100GbE line card with integrated SR-10 optics that can run "triple-speed": 10GbE, 40GbE, or 100GbE ports. To clarify this capability, each individual port on this card can be configured to run as 1x100GbE port, 3x40GbE ports, or 12x10GbE ports using appropriate breakout cables. Because the 100GbE port is made up of multiple 10GbE lanes, Arista is allowing customers to configure the port speeds however they need, never losing use of available lanes just because of a lower speed requirement.

A 36x40GbE line card with modular QSFP optics: Each port can be run at either 40GbE or 4x10GbE ports.

A 48x10GbE line card with two triple-speed 100GbE uplinks and a 48x10GbE line card: Both line cards support 1GbE and 10GbE SFP/SFP+ optics, and have deep buffers and large tables like the other two 7500E line cards.

An Arista 7500 8-slot chassis fully populated with the 100GbE line card is therefore capable of 96x100GbE, 288x40GbE or 1152x10GbE ports in an 11RU (quarter-rack) form factor. That's an awful lot of port density, and remember that all of these ports forward at L2 or L3 line-rate when paired with the 7500E fabric modules.

For customers who don't require line-rate performance but want the port density, the 7500E line cards will run in "mixed-mode", where the chassis contains both E and non-E components.

The 7500E cards put up some other big numbers as well, including 256K host routes, 256K MAC addresses, 256K multicast routes, 256K ARP entries, 64-way multi chassis link aggregation, and 64-way equal-cost multi path. This means the network can grow tall with lots of hosts and routes, but it can also grow wide, with as many parallel paths at both L2 and L3 as a designer is likely to require.

Note that the 7500E is a finalist for the Best of Interop awards in the Networking category.

The 7500E Spine

Arista suggests a leaf-spine data center architecture based on the 7500E, as seen below. The 7500E line cards were built with the spine in mind, sporting some rather deep per-port buffers: 125MB for 10GbE ports, 500MB for 40GbE, and 1000MB for 100GbE. The buffering supports traffic bursts coming in from the leaf tier, where multiple senders capable of sustaining 10GbE or 40GbE flows are trying to reach the same recipient.

Arista's Universal Network Architecture

Image courtesy of Arista Networks

This design is Arista's notion of a "universal network architecture," and it speaks to a significant point Arista is trying to make: build the network once, and be done with it. From Arista's point of view, it doesn't matter what sort of compute model or business application the network needs to support. This architecture, coupled with intelligent placement of workloads, makes for a data center where the network is not in the way.

To push the "network is not in the way" idea even further, the 7500E line cards support per-port VXLAN termination. This means that customers can offload VXLAN encapsulation and decapsulation to the switch hardware, along with moving some overlay configuration complexity out of the hypervisor soft switch tier and onto the network hardware tier.

[ Join us at Interop Las Vegas for access to 125+ IT sessions and 300+ exhibiting companies. Register today! ]

Put another way, this means that a data center architecture based on the 7500E is a complete overlay/underlay approach, in hardware, for virtualized, multi-tenant environments.

Arista also checks the SDN box. The 7500E is OpenFlow 1.0 compliant, and Arista has the OF 1.3 spec on its roadmap. Arista says it has no plans for a controller of its own, intending to be SDN-controller agnostic.

Arista VP Doug Gourlay makes the point. "Our customers should be able to take the network and run it today with the protocols they know. But then say they want to try Nicira...then later PlumGrid, then Big Switch. And then say they want to run OSPF and BGP and IS-IS again. Our customers should be able to do that without changing the hardware, and without changing the software on the edge boxes."

For more on SDN, see Network Computing's exclusive SDN Vendor Comparison site.

Aside from the technology itself, perhaps the most engaging news to come along with the 7500E is the pricing. 10GbE is at $550 per port, 40GbE at $2,200 per port, and 100GbE (including optics) at $10,000 per port. Arista says the 7500E is in production environments at 15 Arista customers, and the product is shipping today. If you want to build a 7500E system, you can order one now.

Ethan Banks, CCIE #20655, is a hands-on networking practitioner who has designed, built and maintained networks for higher education, state government, financial institutions, and technology corporations. Ethan is also a host of the Packet Pushers Podcast. The technical ... View Full Bio
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