Acronym for Internetworking Operating System
Written by Cisco and used in their networking devices, such as Router?s.

Apparently the most ported OperatingSystem since it is ported to all the devices that Cisco have ever sold.

Does this include the Cisco 7xx series? Perhaps LindsayDruett can clarify this point. --DavidHallett

LindsayDruett replies, no, the Cisco 7xx series router uses what is known as the Combinet OS, simply because the 7xx series router was produced by Combinet systems and was rebadged when Cisco aquired that company. The Cisco 7xx is no longer available and has been replaced by the Cisco 8xx which does run IOS.

As a rule, all devices developed by Cisco run on IOS, however, this doesn't apply to devices that were already developed by a company prior to that company being aquired by Cisco.

The following Cisco devices that don't run IOS

Any device labeled Linksys by Cisco Systems

Cisco 7xx - runs Combinet OS (yuck)
Cisco Catalyst 19xx - Menu Driven

The Cisco Catalyst 19xx enhanced edition runs a watered down version of IOS

Cisco Catalyst 30xx - Menu Driven
Cisco Catalyst 2926 - runs on CatOS

The Cisco 2926 is different from the 29xx XL switches which run on IOS

Cisco Catalyst 50xx and 55xx - runs on CatOS

The Route Switch Modules run on IOS

Older Cisco Catalyst 6500 models - You used to have a choice of IOS or CatOS at install time

Earlier models had Route Switch Feature Cards that run on IOS as a separate entity - not the case now

Earlier versions of Cisco Aironet software on the 340 and 350 series - some weird Menu Driven thing via terminal (yuck), but does have a good HTML configuration interface. Cisco have now released IOS for the 350 series units.

The newer Cisco Aironet devices run on IOS (1200s, etc)