• United States
Neal Weinberg
Contributing writer, Foundry

Cisco Catalyst 3750

Sep 16, 20033 mins
Cisco SystemsNetwork SwitchesNetworking

* The Reviewmeister puts Cisco's new line of Catalyst 3750 switches through its paces

The Reviewmeister recently put Cisco’s new line of Catalyst 3750 switches through its paces.

Here’s what we found: With the 3750 line, Cisco has filled the gap between its small, stand-alone Ethernet switches and its large, modular chassis and blade switches.

The Catalyst 3750 stack is a good fit for enterprise applications where a large chassis solution is not economically feasible, and smaller stand-alone switch products don’t scale.

Cisco offers four switch configurations in the Catalyst 3750 line – a 24-port 10/100Base-T switch with two small form-factor pluggable (SFP) uplinks, a 48-port 10/100Base-T switch with four SFP ports, a 24-port 10/100/1000Base-T switch and 24-port 10/100/1000Base-T switch with four SFP ports.

We tested the 24-port Fast Ethernet box tied to both 24-port Gigabit switches.

The switches are interconnected using proprietary multi-pin connectors. Two of these connections per switch are needed to form a ring. The switch hardware load-balances all packets entering the switch onto both directions of the stack ring.

Even if a packet is destined for a port on the same switch it entered, it will be forwarded to the ring. The ring acts as the backplane for all the switches in a stack. In a full-ring configuration, Cisco says it can support 32G bit/sec of throughput.

If a stack cable or switch fails, the neighboring switches will sense the ring disconnect and terminate the ring on both sides of the fault. The ring can support 16G bit/sec in this fault state, Cisco says.

Our tests showed that ring throughput is 26G bit/sec for the smallest allowable packet size and 30G bit/sec for the largest packet size. This difference in bandwidth is most likely because of the extra header information tacked onto each packet entering the ring and the bandwidth used by the token to arbitrate access to the ring. When we introduced a fault in the ring by unplugging one of the ring cables, the ring bandwidth was measured to be about half of the full ring bandwidth, or 15G bit/sec with large packets and 13G bit/sec with small packets.

We also tested the ring configuration for increased latency. The Catalyst 3750 stack racked up a worst-case latency of 50 microsec, which is well below the threshold where latency-sensitive applications would be affected.

The command-line interface (CLI) looks and feels like the standard Cisco interface with the addition of a few commands to configure stack options. The stack appears as a multiple card chassis with the typical hub/slot/port numbering convention. The master switch replicates the CLI to all the switches in the stack so that console port access shows the same information from any switch in the stack. The configuration files are unified for all switches. If the master switch fails, the new elected master will have the configuration for the entire stack.

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