A router is a device that connects two or more packet-switched networks or subnetworks. It serves two primary functions, described below.
- Managing Traffic: Routers forward data packets to their intended IP addresses, ensuring efficient communication between networks. They act as the air traffic controllers for data, directing packets to their destinations.
- Shared Internet Connection: Routers allow multiple devices to use the same Internet connection. Here’s how they work:
- Local Area Networks (LANs): LANs consist of connected devices within a specific geographic area. A single router typically serves a LAN.
- Wide Area Networks (WANs): WANs cover vast geographic areas. Large organizations with multiple locations use separate LANs, which connect to form a WAN. WANs often require multiple routers and switches.
Think of a router as an air traffic controller guiding data packets to their destinations efficiently. It uses an internal routing table to determine the best path for each packet based on its destination IP address12.
Difference Between a Router and a Modem
- Router: Manages data flow within and between networks.
- Modem: Connects networks to the Internet by converting signals from an ISP into a digital format interpretable by devices. Routers distribute this signal to multiple devices within a network, allowing simultaneous Internet access
Main Components of a Router
RAM
Random access memory contains the software and data structures that allow the router to function. The principle software running in RAM is the Cisco IOS image and the running configuration.
ROM
Read-only memory contains microcode for basic functions to start and maintain the router.
Flash Memory
Flash is primarily used to contain the IOS software image. Some routers run the IOS image directly from Flash and do not need to transfer it to RAM.
NVRAM
Non-volatile random access memory is mainly used to store the configuration. NVRAM uses a battery to maintain the data when power is removed from the router.
Configuration Register
The configuration register is used to control how the router boots up.
Interfaces
The physical connections to the external world for the router. These interfaces include the following types: Ethernet and Fast Ethernet, Asynchronous and synchronous serial,Token Ring, FDDI , ATM, Console and auxiliary ports.