Cisco's Catalyst 3550 midrange switch
Layer 3 switch delivers flawless wirespeed performance.
Cisco has designed its new midrange Catalyst 3550-24 switch to connect access devices to the core of large and midsize enterprise networks, and from what we found with our performance testing, it is well equipped for the task.
The Catalyst 3550-24, which ships with 24-port Fast Ethernet and two-port Gigabit Ethernet capacity, earned its strong overall score because of its near-perfect performance in our tests. The box produced wirespeed throughput even while handling access control lists (ACL) we intentionally applied to try to slow it down. The only fault was with the Web-based management interface called Cluster Management Suite (CMS). The interface is usable but a little buggy, as noted when we tested it on other Cisco midrange switches. Basic Layer 3 performance is picture-perfect with wirespeed throughput throughout our suite of tests and only a 120-microsec latency measurement with 64-byte packets.
Performance charts (PDF)
How we did it
In addition to our basic throughput tests, we set up several ACL entries to see how the switch reacted to heavy network traffic loads. Usually an ACL will bog down the processor of a router or switch of this type, which reduces the sustainable throughput and increases packet latency. The Catalyst 3550-24 showed no signs of performance degradation with an ACL enabled. This is rare for this class of Ethernet switch.
Our three routing tests showed that the Catalyst 3550-24 can maintain 64,000 external routes for Open Shortest Path First (OSPF) and 4,500 routes for Routing Information Protocol (RIP) in its route table. It's one thing to be able to support dynamic routing protocols, but it's another thing to handle dynamic routing when certain links or devices are intermittent. While sending traffic at 90% wirespeed, we advertised 80% of the route table capacity to the switch, withdrew 50% of the resulting routing table and then readvertised the withdrawn routes. The Catalyst 3550-24 showed good stability while simulating a hostile routing scenario by quickly reacting to all the routing changes.
The Catalyst 3550-24 implements rate-limiting ACLs perfectly, which is a good ability to have if you need to set a traffic ceiling on certain problem flows such as Web surfing traffic. In terms of quality-of-service (QoS) features, the four egress queues on each port work as advertised. Our testing showed that the 3550 can drop packets appropriately under congestion and send higher-priority packets through more quickly while the ports are not congested.
In addition to its OSPF and RIP features, the Catalyst 3550-24 ships with other typical Layer 2 and Layer 3 capabilities, including support for virtual LANs, fast Spanning Tree Protocol, Interior Gateway Routing Protocol and Enhanced Interior Gateway Routing Protocol.
Software upgrade delivers core switch features
The Catalyst 3550-24 comes with a Standard Multilayer Software Image (SMI), but our test unit was upgraded to include the Enhanced Multilayer Software Image (EMI). The EMI provides more enterprise-class features such as hardware-based IP unicast and multicast routing, intervirtual LAN routing, and support for Hot Standby Router Protocol. The switch can be upgraded from SMI to EMI after deployment.
The Catalyst 3550-24 has features usually reserved for core-class enterprise switches, including ACLs, rate limiting, weighted round robin queuing and Differentiated Services code point. Our testing showed that these features work as advertised.
The switch is scalable if it's used for what it's designed to do. Cisco claims it can support up to 16,000 routes. We confirmed 64,000 routes with OSPF but only 4,500 routes using RIP. Even though it doesn't live up to marketing claims, 4,500 routes should be plenty to handle most enterprise networks.
To help ease the difficulties with configuring the feature-rich Catalyst 3550-24, Cisco included its CMS with this bundle. CMS is a Java-based, Web-accessible management interface with built-in configuration wizards to ease the setup of the Catalyst 3550-24 and to help customers implement applications such as voice over IP and network security.
CMS is a great idea because it offers an easy feature-configuration interface - especially for setting up QoS parameters - but the overall implementation is far from perfect. We noticed several bugs in the interface. CMS shows the wrong value in the rate-limit configuration - it showed 50K bit/sec instead of 50M bit/sec, and we had to reboot the switch for the rate limit we configured to become effective.
The Catalyst 3550-24 can be configured and monitored through the Cisco command-line interface and SNMP.
Installation and initial setup is a breeze. CMS certainly helps with setting up the switch out of the box, even with its bugs. Alternatively, the IOS setup command helps users through the configuration process. The documentation with the switch helps users rack the switch and power it up. Beyond that, they must use Cisco's extensive Web documentation to learn how to configure the switch software.
The Catalyst 3550-24 has a lot of great features with good performance to back it up. This would be a great switch for midsize to large enterprise networks needing a multilayer switch with the capacity to handle large amounts of bandwidth and features to manage applications flowing over the network.
Bass, a senior technical staff member at CNL and co-author of McGraw Hill's Building Cisco Multilayer Switched Networks, designs and leads the execution of the test suites. He can be reached at firstname.lastname@example.org. Sangram Kadam and Khurram Khan assisted with the testing.www.nwfusion.com/alliance.
How we did it
Our testing methods explained.