| 2.1 |  | Operating Cisco IOS Software |
| 2.1.4 |  | Cisco IOS software features |

| Cisco provides IOS images for devices spanning a wide range of network product platforms. To optimize the Cisco IOS software that these various platforms require, Cisco is working to develop many different Cisco IOS software images. Each image represents a different feature set that serves the various device platforms, available memory resources, and customer needs. Although there are numerous IOS images for different Cisco device models and feature sets, the basic configuration command structure is the same. The configuration and troubleshooting skills acquired on any one device apply across a wide range of products. The naming convention for the different Cisco IOS releases contains three parts: The platform on which the image runs The special features supported in the image Where the image runs and whether it has been zipped or compressed Specific IOS features can be selected using the Cisco Software Advisor. The Cisco Software Advisor is an interactive tool that provides the most current information and allows the selection of options that meet network requirements. One of the main considerations when selecting a new IOS image is compatibility with the router flash and RAM memory. In general, the newer the release and the more features that it provides, the more memory it requires. Use the show version command on the Cisco device to check the current image and available flash. The Cisco support site has tools available to help determine the amount of flash and RAM required for each image. Before installing a new Cisco IOS software image on the router, check to see if the router meets the memory requirements for that image. To see the amount of RAM, issue the show version command: … <output omitted>… cisco 1721 (68380) processor (revision C) with 3584K/512K bytes of memory. This line shows how much main and shared memory is installed in the router. Some platforms use a fraction of DRAM as shared memory. The memory requirements take this into account, so both numbers have to be added together to find the amount of DRAM installed on the router. To find out the amount of flash memory, issue the show flash command: GAD#show flash … <output omitted>… 15998976 bytes total (10889728 bytes free)