Arista 10G switch: Fast and flexible

Linux-based core switch sets records with high density, blazing performance

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That's certainly more than enough for most data centers, though routing capacity is also a topic of some specsmanship among vendors. In its internal testing, Arista says the 7508 learned 42,500 routes when the advertised networks primarily used /24 and /32 prefix lengths (we used an Internet distribution in our tests, modeling the prefix lengths seen on Internet backbones).

We've previously tested other modular systems with much higher capacity; the record-holder is still the 3Com (now HP) S7906E, which learned more than 200,000 routes over OSPF. Further, Internet-facing routers running BGP will need far higher capacity; one view of a full BGP table is about 400,000 routes, and many sites will have multiple BGP feeds.

But this is a core data center switch, not a core router. Distinctions between 10,000 and 200,000 or 400,000 routes or more simply aren't meaningful for the vast majority of enterprises running OSPF; even in very large data centers, 10,000 routes is plenty.

Another part of the EOS routing feature set is the ability to load-balance using OSPF ECMP, distributing traffic on as many as 16 links. Most competitors support a maximum of eight-way links when doing ECMP.

In our tests, the 7508 spread traffic pretty evenly across all 16 OSPF sessions. We saw a variation of around 1.215% between the least and most used OSPF ports.

Our complaints with the 7508 are relatively minor. Unicast maximum latency is higher with short- and medium frames than longer frames. The 7508's hardware routing table doesn't scale as high as some other modular switches we've tested, but that's more a battle for bragging rights among vendors than a concern for most data centers. EOS doesn't yet support hitless failovers or IPv6, though Arista says it's working on both. And the 7508's buffering capabilities differ depending on traffic patterns, but that's true of all credit-based systems.

Speed and flexibility trump these complaints. As enterprises roll out more 10G Ethernet in the data center - and that will happen soon - they'll need high-density ways to tie everything together. The Arista 7508 is ready to do that, today.


Network World gratefully acknowledges the assistance of Spirent Communications, which supplied its Spirent TestCenter traffic generator/analyzer and 10G Ethernet HyperMetrics dX modules for this project. Spirent's Jurrie van den Breekel and Timmons Player also provided technical support. Thanks also to Fluke Corp. for supplying a Fluke 335 clamp meter used in power measurement.

Newman is a member of the Network World Lab Alliance and president of Network Test, an independent test lab and engineering services consultancy. He can be reached at

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Copyright © 2012 IDG Communications, Inc.

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