Router Internal Components Video Transcript
Router Internal Components Ray Moore Professor Gateway Community College Length: 3:37 The router is a special purpose computer that has a central processing unit, memory, interfaces, and an operating system just like any other computer. Let’s take a look inside a router. This is a Cisco 2514 router. Before we take off the cover, we need to take a few safety precautions. Static electricity can be damaging to electronic components, so we have our router on an anti-static mat. Also, here’s an anti-static wrist strap. We put it on and fasten it to the chassis of the router. If we have any static electricity, it will be safely removed by either of these devices. We remove the screws and then remove the cover. This is the central processing unit, or CPU, of the 2500 series router. It’s a Motorola 68030 chip - the same type is used in the Macintosh II computer. Here are the boot ROMs. They contain a scaled down version of the operating system. To change the version of the operating system in the ROM, you need to replace both of these ROM chips. When the router is turned on, it does a power-on self-test, or POST. This checks the components of the router to make sure that they’re working correctly. When the test has passed, a bootstrap loader program is executed from the boot ROMs. Next, the full operating system, the Cisco IOS, is loaded from flash memory located here. Flash is electronically erasable, programmable, read-only memory, or EEPROMs. You’ll notice that there’s space for two modules in this particular router. You can add or replace these modules to increase the size of the flash. If you have enough flash, you can store different versions of the IOS on the router at the same time. A portion of the operating system is loaded into random-access memory, or RAM, located here. There is room for only one module in the 2500 series router. But you can replace this module with one of a larger capacity to increase the memory of the router. Part of the operating system that’s held in RAM is the command executive, or exec. Exec receives the commands entered into the router and performs or executes these commands. Some of the other types of things kept in RAM are the running configuration, the ARP cache, packet queues, routing tables, memory buffers as well as temporary storage for the operation of the router. When the power to the router is shut off, everything that was in RAM is lost. We keep a copy of the router configuration in NVRAM, or nonvolatile randomaccess memory. NVRAM doesn’t lose its contents when the power to the router is shut off.
1-2
Video: Router Internal Components
Copyright 2001, Cisco Systems, Inc.
This is the power supply. It takes in the AC voltage from the wall and converts it to DC voltage for use in the router. Notice that there is a fan with the power supply. This is to dissipate the heat that results from the transformer that converts the voltage from AC to DC. As well, the fan dissipates the heat that results from the electronic components in the router. Interfaces allow us to hook up the router to the outside world. The interfaces of the 2500 series router are located here. If you think about a router and relate its internal components to those of the personal computer, the router becomes less of a mystery and something that you can become comfortable with.
Copyright 2001, Cisco Systems, Inc.
Video: Router Internal Components
1-3
