Comparison: CatOS and Cisco IOS

In most cases, the technology for the Cisco Catalyst Switch was established separately from Cisco′s router technology. The Cisco Catalyst Switch initially ran software called CatOS rather than the more generally known Cisco IOS software used by routers.

However, this has changed as the product lines have combined closer together. In some cases, mainly 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 abolished CatOS entirely in favor of IOS, even on hardware that initially required CatOS. One newer Cisco Catalyst Switch models (with recent versions of the Cisco IOS) also permit configuration via web-based graphical interface (GUI) module which is presented on a HTTP server located on the Cisco Catalyst Switch. The IOS config-mode command 'ip HTTP-server' will enable this grace of configuration.

Fig 1.1- CatOS and Cisco IOS 
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 permits this style of GUI configuration via HTTP.

Some latest models of Cisco Catalyst Switch (called Catalyst Express) no longer permit access to IOS or CatOS at all - these switches can only be configured by using a GUI.

CatOS (Catalyst Operating System) is the withdrawn operating system for many of the Cisco Catalyst Switch brand of heritage network Cisco Catalyst Switch It was initially called "XDI" by the switching company Crescendo Communications, Inc. Cisco renamed it to CatOS when they acquired Crescendo in late 1993.

CatOS ran on Cisco Catalyst Switch such as 1200, 2948G, 4000, 4500, 5000, 5500, 6000, 6500 series. CatOS can still run on some of Cisco's modular switches, "hybrid" mode. In hybrid mode, the NMP (switch processor) runs CatOS and the route processor runs Cisco IOS.

CatOS and IOS Comparison

There are actually three flavors of the operating system for certain Cisco Catalyst Switch: CatOS, hybrid mode, and native mode (IOS). CatOS configures only Layer 2 switching. For Cisco Catalyst Switch that have Layer 3 capabilities, such as the Catalyst 6500 with the MSFC (multilayer switch feature card), CatOS can be used for Layer 2 functionality and the IOS can control the MSFC. This process is called hybrid mode.

Fig 1.2- CatOS and Cisco IOS command Comparison

In native mode, the IOS controls both Layer 2 and Layer 3 functions in the switch. Table 2.5 displays the Cisco Catalyst Switch and the modes that they support.