Catalyst switch

Catalyst is the brand name for a variety of network switches sold by Cisco Systems. While commonly associated with Ethernet switches, a number of different interfaces have been available throughout the history of the brand. Cisco acquired several different companies and rebranded their products as different versions of the Catalyst product line. The original Catalyst 5000 and 6000 series were based on products originally developed by Crescendo Communications. The 1700, 1900, and 2800 -series Catalysts came from Grand Junction Networks, and the Catalyst 3000 came from Kalpana in 1994. [ [http://www.ciscopress.com/articles/article.asp?p=25172&rl=1 Configuring the Catalyst > Configuring the Catalyst ] ]

In addition, Cisco increasingly offers routers with switching capabilities, and indeed Cisco's 7600 router line and 6500 switch line have interchangeable parts. Even Cisco's smaller routers, including their newest "ISR" series, can have switch modules installed in them - basically making Cisco's smaller switches fully integrated devices.

Operating systems

In most cases, the technology for the Catalyst Switch was developed separately from Cisco's router technology. The Catalyst switches traditionally ran software called CatOS rather than the more widely known Cisco IOS software used by routers. However, this has changed as the product lines have merged closer together. In some cases, particularly in the modular chassis switches, a configuration called 'Hybrid' has emerged - this is where the layer 2 functions are configured using CatOS, and the layer 3 elements are configured using IOS. 'Native IOS' can also be found with newer software versions that have eliminated CatOS entirely in favor of IOS, even on hardware that originally required CatOS.

The latest version of IOS for the Catalyst 6500 series is 12.2(18)SXF5 which enables ISSU via IOS Software Modularity.

Some newer Catalyst switch models (with recent versions of the Cisco IOS) also allow configuration via web-based graphical interface module which is hosted on a HTTP server located on the switch. The IOS config-mode command 'ip http-server' will enable this style of configuration. In series 12.x IOS, 'ip http-server' is always on as a factory default. The Catalyst 3750-series of switches is an example of a Cisco Catalyst switch that allows this style of GUI configuration via HTTP.

Some newer models of Catalyst switches (called Catalyst Express) no longer allow access to IOS or CatOS at all - these switches can only be configured by using a Graphical User Interface (GUI).

Interfaces

As Catalyst devices are primarily Ethernet switches, all modern Catalyst models have Ethernet interfaces, ranging from 10 Mbit/s to 10 Gbit/s depending on the model. Some models can accommodate Asynchronous Transfer Mode interfaces which can be used to bridge Ethernet traffic across wide area networks. Other models can support T1, E1, and ISDN PRI interfaces to provide connections to the PSTN. Legacy models supported a variety of interfaces, such as token ring, FDDI, and 100BaseVG, but are no longer sold by Cisco Systems.

Features

Most models have basic layer 2 functions and are capable of switching Ethernet frames between ports. Commonly found additional features are VLANs, trunking (Cisco proprietary ISL or IEEE 802.1Q) and QoS or CoS. The switches, whether IOS or CatOS, are fully manageable.

Many Catalysts that run IOS are also capable of functioning as a router, making them layer 3 devices; when coupled with TCP and UDP filtering, these switches are capable of layer 2-4 operation. Depending on the exact software image, a Catalyst that runs IOS may be able to tackle large-scale enterprise routing tasks, using router technologies like OSPF or BGP.

Most chassis-based Catalyst models have the concept of field-replaceable "supervisor" cards. These work by separating the line cards, chassis, and processing engine (mirroring most Cisco router designs). The chassis provides power and a high-speed backplane, the line cards provide interfaces to the outside world, and the processing engine moves packets, participates in routing protocols, etc. This gives several advantages:
* If a failure occurs, only the failed component needs to be replaced (typically a line card or supervisor). This means faster turnaround than having to uncable, unbolt, pull out, replace, re-bolt, and re-cable an entire switch, which may be as large as a quarter-rack, weigh over 150 pounds, and service over 500 cables.
* A redundant supervisor engine may be installed to rapidly recover from supervisor failures. This is subject to restrictions (as some switches don't support redundant supervisors), but typically results in restoration times under 90 seconds.
* A supervisor engine may be upgraded after purchase, increasing performance and adding features without losing any investment in the rest of the switch.

Additionally, most high-end switches off-load processing away from the supervisors, allowing line cards to switch traffic directly between ports on the same card without using any processing power or even touching the backplane. Naturally, this can't be done for all traffic, but basic layer-2 switching can usually be handled exclusively by the line card, and in many cases also more complex operations can be handled as well.

Management

Cisco switches are very popular for a number of reasons, including advanced customization and manageability. The switches can be configured using a serial console or a telnet session (or ssh if the correct OS is loaded along with the ssh keys generated). SNMP allows monitoring of many states, and measurement of traffic flows. Many devices can also run an HTTP server, but this is often disabled because of the security problems it creates - either because it's not encrypted, or because of the relatively frequent security vulnerabilities in the Cisco httpd daemon itself.

Configuration of the switch is done in plain text and is thus easy to audit - no special tools are required to generate a useful configuration. For sites with more than a few devices it is useful to set up a TFTP server for storing the configuration files and any IOS images for updating. Complex configurations are best created using a text editor (using a site standard template), putting the file on the TFTP server and copying it to the Cisco device. However, it can be noted that an TFTP server can present security problems.

Models

Like most Cisco product lines, the Catalyst Switch series evolves fairly rapidly. There are two general types of Catalyst switches: fixed configuration models that are usually one or two rack units in size, with 12 to 80 ports; and modular switches in which virtually every component, from the CPU card to power supplies to switch cards, are individually installed in a chassis.

* As of 2008, the most popular fixed configuration switches are the WS-C2950, WS-C2960, WS-C3550, WS-C3560, and WS-C3750 series (some of which are already at their end of life, even though still widely used). These switches come with a bewildering assortment of features (10/100 ports versus 10/100/1000 ports, some with power over ethernet, some with varying types of gigabit uplink ports, some with standard or enhanced software) and it is difficult to tell from inspection the switch type. ISPTrader (http://isptrader.com/switches.htm) has an excellent discussion and description explaining the difference between the lines and how to decipher the model features from its model name.

In general, WS-C2950 and WS-C2960 switch series have 10/100 ports, WS-C3550 and WS-C3560 switches add full gigabit capabilities and power over ethernet (PoE), and the WS-C3750 series adds a 'stackwise' feature that allows multiple physical switches to operate as a logical, single switch.

Older fixed configuration switches that are adequate for most small business include the WS-C2912 and C2924 XL-EN series(the forerunning of the WS-C2950 series) and the WS-C3524 and C3548 XL-EN series (the forerunner of the WS-C3550 series).

Cisco modular switches are much larger, and include the following:

* The Cisco Catalyst 6500 Series is a chassis-based switch family. This series can support interfaces up to 10 gigabit Ethernet in speed and redundant Supervisor modules.

* The Cisco Catalyst 5500 Series and Cisco Catalyst 5000 Series is a chassis-based switch family. Cisco Catalyst 5000 Series is acquired from other company. This entire series has now reached end-of-sale.

* The Cisco Catalyst 4900 series is a fixed-configuration switch. Uplink interfaces are either SFP ports or 10 gigabit Ethernet, with 48 copper ports of 10/100/1000 Ethernet.

* The Cisco Catalyst 4500 Series is a chassis-based switch family. This series can support uplinks up to 10 Gbit/s in speed and redundant Supervisor modules (R-series Models only).

The 1000 switch family is considered an edge device, having many functionalities that can be built as the device is very modular.

* 1700: 24 10BaseT ports, 1 switchable MDI/MDIX uplink 10baseT/AUI/BNC port, and 2 Fast Ethernet ports. Runs neither CatOS nor IOS. Is a first-generation carryover from Cisco's acquisition of Grand Junction Networks.
* 19xx: 12 or 24 10BaseT ports and 2 Fast Ethernet ports. ISL trunking on the 100 Mbit/s ports. Runs neither CatOS nor IOS.

References

* [http://newsroom.cisco.com/dlls/2006/fin_080806.html Cisco Systems Fourth Quarter and Fiscal Year 2006 Earnings]
* [http://www.townsendassets.com/company/catalyst_6500_article.htm Cisco's Catalyst 6500 Remains the Network Switch to Beat]
* [http://www.crn.com/showArticle.jhtml?articleID=193004953 10-Gigabit Ethernet Poised To Take Data Centers By Storm]

External links

* [http://www.cisco.com/ Cisco Systems Home Page]
* [http://www.cisco.com/univercd/cc/td/doc/product/lan/index.htm Cisco's Product Documentation Website for Catalyst Switches]
* [http://cosi-nms.sourceforge.net Cisco-centric Open Source Community]
* [http://network-emulators.com Cisco Switch/Aironet/Router/PIX simulator/emulator]