Router CPU and Memory Although there are several different types and models of routers, every router has the same general hardware components.
Depending on the model, those components are located in different places inside the router. Figure 6 shows the inside of a Cisco1841 router.
Figure 6. Hardware Components of a Router Similar to a PC, a router also includes CPU RAM ROM Flash memory NVRAM CPU The CPU executes operating system instructions, such as system initialization, routing functions, and network interface control. RAM Similar to other computers, RAM stores the instructions and data needed to be executed by the CPU. RAM is volatile memory and loses its contents when the router is powered down or restarted. For this reason, the router also contains permanent storage areas such as ROM, flash, and NVRAM. ROM ROM is a form of permanent storage.
Cisco devices use ROM to store Bootstrap instructions Basic diagnostic software Scaled-down version of IOS ROM uses firmware, which is software embedded inside the integrated circuit. Firmware, such as the bootup instructions, does not normally need to be modified or upgraded. Many of these features, including ROM monitor software, will be discussed in a later course.
ROM does not lose its contents when the router loses power or is restarted. Flash Memory Flash memory is nonvolatile computer memory that can be electrically erased and reprogrammed. Flash is used as permanent storage for the operating system. Internetwork Operating System (IOS) The operating system software used in Cisco routers is known as Cisco Internetwork Operating System (IOS).
Like any operating system on any other computer, Cisco IOS Software is responsible for managing the hardware and software resources of the router, including allocating memory, managing processes and security, and managing file systems.
Cisco IOS is a multitasking operating system that is integrated with routing, switching, internetworking, and telecommunications functions. To learn more about packet forwarding, check the following sites: Router hardware components (http://www.juniper.net/techpubs/en_US/junos13.1/topics/concept/junos-software-routing-platforms-hardware-components.html) Cisco device hardware components (http://computernetworkingnotes.com/cisco-devices-administration-and-configuration/router-booting-process.html) Cisco Internetwork Operating System (http://www.cisco.com/en/US/products/sw/iosswrel/ps1818/products_tech_note09186a008015083e.shtml) CCNA router and IOS basics (http://www.slideshare.net/dsunte/ccna-router-and-ios-basics) Assignment You are required to review the SLP materials and conduct your own research (at least three additional sources of materials. Please be sure to use appropriate citations for materials that you collect on your own), in your own words, please write a 2- to 3-page paper (excluding the cover page and reference page) to describe the hardware and software components of a router, and how the router stores the OS while running. You may pick one kind of router, e.g. one of Cisco 1800 series router. SLP Assignment Expectations Your paper should be between two and three pages. You are expected to understand the components of a router. Upload your assignment when it is finished.
