Although a router is a very specialised network device that can be configured to suit the needs of the network, including routing and security tasks, it is in many ways similar to a standard PC computer system in the sense that it has many components and behaviours in common with a computer system.
Compare a the components of a router with that of a Personal Computer system;
A Computer System (PC) contains the following items;
A Router contains the following items
As can be seen from the above list, a computer system and a router have many common components (PCs may have other components, however many of the basic components are similar)
One of the most recognisable ways that a router is similar to a PC is in the fact that they both have an operating system. Prior to this operating system being loaded, both devices go through a boot-up process.
In a PC, the system BIOS will run a power on self test (POST) which checks critical components and reports any faults. The BIOS also contains configurable settings that allow the administrator to for example change where the computer system will look for a boot device.
A router goes through a very similar process, it will carry out a POST, the router will then look to boot an operating system. An administrator can determine where the router will look to boot this operating system.
The main components of a router are: RAM, NVRAM, ROM and its interfaces.
RAM stores the current running configuration of the router (the current settings it is using) The RAM of the router also stores the routing tables (these are used to help the router determine the best path for a packet through the network). RAM, like the RAM on a PC, is volatile and loses its contents when power is removed.
NVRAM holds the start-up configuration file. This is the set of instructions that the router will work towards. These are copied to RAM and called the running configuration on start up. NVRAM is not volatile (NV stands for non-volatile) and retains its contents on powering down.
ROM holds the bootstrap program that loads the BIOS and carries out POST.
FLASH memory uses EEPROM and contains the operating system files, as it is EEPROM it can be renewed without replacing the chip and doesn’t lose its contents when it has no power.
The operating system on routers is primarily still a command line interface. This is due to the fact that most of the processing power of the router is concentrated on carrying out its main task which is forwarding packets. Modern routers do now contain a graphical user interface which can assist in configuring advanced techniques such as security and encryption.