Cisco take note: Juniper's new EX 4200 switch not only fills a hole in a leading competitor's product line, but also represents a credible alternative for enterprise access switching.

In Network World's exclusive Clear Choice test, we subjected the EX 4200-48T switch to the same rigorous battery of benchmarks we used to assess seven other vendors' 10G Ethernet access switches earlier this year. (See comparative 10G Ethernet switch test.)

The verdict: This is one fast box. The EX 4200 delivered line-rate throughput in every case, the only switch we've tested this year to do so. What's more, 10G Ethernet latency is the lowest we've ever measured. We also were impressed by the EX 4200's feature set and powerful JUNOS command-line interface (CLI).

That's not to suggest Cisco and others should fold up their tents, though. This is Juniper's first effort in enterprise switching, and that inexperience shows in a few places. Multicast support is still a bit rough, and our tests also uncovered a couple of security concerns. Still, this is an impressive device, especially for a first try.

We tested the US$16,800 EX 4200-48T, which offers 48 10/100/1000Mbps gigabit ports, two 10G Ethernet ports, PoE capability on 8 ports, and stacking capability for up to 10 switches. Juniper also offers the EX 4200-48P with 48 ports of PoE capacity from a single power supply for $18,400. Both devices offer optional redundant power supplies and support virtually all switching and routing protocols.

Faster still

In access switch tests earlier this year we found throughput no longer is the differentiator as it once was, with most boxes pushing packets either nearly at, or within one percent of, line rate.

With Juniper's EX 4200, there's no need to say "nearly". Even under the heaviest loads our Spirent TestCenter traffic generator threw at it, the switch delivered line-rate throughput in every single unicast and multicast test, both in layer-2 and layer-3 configurations. No other switch did that.

Latency -- often a more important metric than throughput, especially for time-sensitive voice and video traffic -- was low and consistent across all tests. Measured at line rate, the Juniper switch delayed 64-byte frames across 10G Ethernet links for an average of 1.96 microsec and a maximum of 2.01 microsec.

Those are the lowest latencies we've ever recorded in an Ethernet switch. In fact, even the maximum latency of the EX 4200 is less than the lowest average result we measured in the previous round of tests.

With large 1,518-byte frames, latencies hovered in the 2 to 3 microsec range on 10G Ethernet ports and in the 20 to 30 microsec range on gigabit Ethernet ports. The gigabit numbers are either comparable to or better than most other switches we've tested; the 10G Ethernet latencies, again, set record lows.

Multicast latency also hovered in the low microseconds, compared with numbers that in some cases were dozens of times higher in previous tests. The Juniper switch won't hold up traffic long enough to adversely affect the performance of any enterprise application.