Router

What is a Router?

Routers are essential parts of networking. A router is commonly used when accessing the internet or when sharing files over an office network. But what exactly is a router, and how does it work? A router is a basic physical or virtual appliance that exchanges information between two or more packet-switched computer networks. A router is a bridge that checks a given data packet’s destination Internet Protocol address (IP address). It calculates the best way for it to reach its destination and then forwards it accordingly.

A router is Basically a common gateway. It exists at the point where two or more networks meet at each point of presence on the internet. It’s possible to have hundreds of routers work together to forward a single packet as it moves from one network to the next on the way to its final destination. The routers are directly associated with the network layer in an Open Systems Interconnection (OSI) model (Layer 3). There are also Traditional routers which are stand-alone devices that use proprietary software.

In contrast to traditional routers, a virtual router is a software router instance that performs the same functions as a physical router. Virtual routers are often found running on commodity servers, either alone or packaged with other virtual network functions, like firewall packet filtering, load balancing, and wide area network (WAN) optimization capabilities.

Some other network devices have built-in router functionality, such as wireless access points and switches.

How a router works?

A router does its job by examining a packet header’s destination IP address and comparing it against a routing table to determine the packet’s best next hop. These routing tables contain directions for forwarding data to particular network destinations, sometimes in the context of other variables, like cost. Together, the tables become an algorithmic set of rules that calculate the best way to transmit traffic toward any given IP address. On a routing table, there is a specified default route that packets can take. This route is a fallback which the router uses whenever it fails to find a better forwarding option for a given packet. An example would be your typical home office router. This router directs all outbound traffic along a single default route to its internet service provider (ISP) for connection and billing.

Routing tables vary in their content and can be static — i.e., manually configured — or dynamic. The routing tables on dynamic routers are automatically updated depending on the current network activity. The updated tables are constantly exchanging information with other devices via routing protocols. Network address translation (NAT) is common among many routers. NAT is a useful feature that shields a local area network (LAN) by readdressing all outgoing traffic with a single shared public IP address. This helps to effectively conserve globally valid IP addresses and also improve network security.

Here’s a list of all the major types of routers out there.

Core routers

Coore routers are used by most Internet Service Providers (ISPs) and are the fastest and most powerful kind of router. They sit at the center of the internet and constantly transfer information along the main fiber optic backbone. In addition, enterprise routers connect large organizations’ networks to these core routers.

Edge router

Edge routers are also called access routers, and they have lower capacity than the core routers. Edge routers exist at the boundary of a LAN and connect it to the public internet or a private wide area network (WAN) and/or external local area network (LAN). Examples of edge routers are Home and small office routers, which are considered subscriber edge routers.

Branch routers

Branch routers are unique routers that link an organization’s remote office locations to its WAN, thereby connecting to the primary campus network’s edge routers. In addition, these routers have other useful features like time-division multiplexing, wireless LAN management capabilities, and WAN application acceleration.

Logical routers

A logical router is simply a certain reconfigured partition of traditional network hardware or physical router. It is designed to replicate the functionality of the hardware and create multiple routing domains within a single router. These kinds of routers perform a subset of the tasks that can be handled by the physical router, and each can contain multiple routing instances and routing tables. 

 Wireless routers

These routers operate similarly to routers in a hard-wired home or business local area network (LAN). These routers are. Different from the traditional routers because they allow for greater mobility for notebooks or portable computers. Virtually every wireless router uses the 802.11g specification, a standard that offers transmission over short distances.

Router Protocols

Routing protocols are instructions that decide how a router identifies other routers on the network, keeps track of all possible destinations, and makes dynamic decisions for where to send each network message. Below is a list of some popular router protocols. 

Open Shortest Path First (OSPF) – This protocol is utilized to find the best path for packets as they pass through a set of connected networks. OSPF protocols are designated by the Internet Engineering Task Force (IETF) as one of several Interior Gateway Protocols (IGPs)

Border Gateway Protocol (BGP) – another popular router protocol. This one is in charge of how packets are routed across the internet by exchanging information between edge routers. BGP helps improve stability and guarantees that routers will quickly adapt to send packets through another reconnection if one internet path goes down.

Interior Gateway Routing Protocol (IGRP)- this protocol decides how routing information between gateways will be exchanged within an autonomous network. The routing information obtained with this protocol can then be used by other network protocols to specify how transmissions should be routed.

Enhanced Interior Gateway Routing Protocol (EIGRP) – evolved from IGRP.  If a router can’t find a route to a destination in one of these tables, it queries its neighbors for a route, and they, in turn, query their neighbors until a route is found. When a routing table entry changes in one of the routers, it notifies its neighbors of the change instead of sending the entire table.