What is a Router in Networking and How it Works?

A router ensures that all data on the LAN or WAN is sent where it needs to go and sent in the most efficient way. They are also useful tools for getting the best performance from an Intranet network.

What is a Router in Networking and How it Works?

Understanding the Working Principle of a Router

A Router opens the IP packet to read the destination address, calculate the best route, and then send the packet to the final destination, and if the destination is in a local network, it sends the packet directly to the receiving computer.

If the packet is targeted for another network or subnet, the router takes into account factors such as traffic congestion and Hop, which refers to the number of routers or gateways on a particular route.

The IP packet configures a section with it that counts hops, and a router does not use a network that exceeds the predetermined hop count.

Therefore, it takes into account the acceptable number of Hops to ensure data can be transmitted.

For example, if there is no direct path between A and B, advanced devices will likely send data to destination B by an Intranet or another router located in another city.

Routers have two or more physical ports such as Receive/Inbound and Send/Out.

Each port is bi-directional so it can receive or send data. When a packet is received on the incoming port, a software process called the routing process begins.

As a result of this process, the header information in the IP packet is searched and the address where the data is sent is found. It then compares this address with a database called the routing table.

If it finds a record about this IP address in the routing table, it forwards the packet to a specific outgoing port. Then the output port then sends the data to the next router or destination.

Sometimes these packets are sent to the router’s incoming port before they are processed, and the packets are sent to a special area called the Input Queue, which is a RAM space on the router.

This Input Queue field is associated with a specific incoming port. In this case, if more than one incoming port sends packets faster than the router can handle, a Router may have more than one Input Queue area.

Each inbound port processes the packets in the queue in the order they are received, and if the passing traffic is heavy, the number of packets in the queue may be more than capable.

In this case, the packets are dropped and therefore will not be processed by the device and sent to their destination, but this does not mean that the information should be lost.

The TCP protocol is designed with the possibility of packets getting lost on their way to their destination. So, if all packets are sent to the TCP receiver, the receiving computer reviews the lost packets and requests them to be sent again. In this case, TCP will send request requests until it has received all of the packets.

Advanced Routers can be managed and problems can be diagnosed and resolved using special software such as the SNMP protocol.

TCP can confirm a response to a previous communication by using a checkered flag in the packet, such as the hop count in IP. There are several types of tables that are configured to be sent to the destination. The simplest of these are static routing tables used in a small Intranet network.

Since an Intranet network is created from a single TCP/IP network, minimal redirects can be used. To examine these minimal redirects, it can be learned with the ifconfig command using the CMD command prompt on the operating system.

When there are few areas where data can be sent, only a minimum number of routers need to be configured.

If a network has only a limited number of TCP/IP networks, a static routing table can be used. In this case, packets with specific addresses are sent to specified routers. Static routing should be used when there is only one route to each destination.

Dynamic routing tables are the most complex. They should be used when there are multiple ways to send data from a router to the final destination and in more complex networks.

These tables constantly change as network traffic and conditions change, so they examine the current state of network traffic and always direct data to the best possible path.

Dynamic routing tables are created using routing protocols. These protocols are used to communicate between routers providing information about the most efficient way to route data.

A router with a dynamic routing table can redirect data to another route if the primary path is narrow. Routers can use this information in an algorithm to calculate the best way to send packets.

A basic routing protocol that performs these calculations is RIP (Routing Information Protocol).

The Exterior Gateway Protocol (EGP) is used on the Internet where many more routers have to switch before a packet reaches its destination.

What Does It Do?

A Router can connect multiple networks together for communication and route network traffic between them. Your router in your home network is the bridge between an internet connection and your private local network. In addition, routers have a switching function that connects different devices and they have a radio through which they can access WiFi.

The router has the ability to be located between your internet connection and your local network and link them together. It allows you to connect several devices to the internet at the same time over the same physical internet connection, communicate with each other over a local network, or allow a web host to global communication.

It also provides protection for all your connected devices and keeps track of what data is transmitted to which device on the network.

Using Filtering

Filtering configured on routers can be the first line of defense against attacks on the local network. Filtering routers examine and analyze every packet moving between networks on an intranet.

A network administrator can set some rules to decide which packets the routers allow or deny.

Therefore, different rules can be set for incoming and outgoing packets, so that while Intranet users access Internet services, anyone on the Internet is prohibited from accessing certain services or data.

More detailed network analysis can be made by recording the flow of this traffic on the device separately. If filtering is not done on the router, packets will pass between the Internet and Intranet without permission, indicating that the network is vulnerable.

Filtering source addresses are read from the IP header and compared against the list of source addresses in the filter tables.

Because network administrators know some addresses are dangerous, they include them in the table, allowing the router to deny this traffic.

The router examines the data in the IP header surrounding the data and header information of the transport stack. In this case, any packet contains two sets of headers for the data and one for the transport stack and one for the Internet stack.

Since different security levels can be set on routers, different rules can also be set for subnets. For example, more restrictive permissions can be configured for the department of the company that contains important data. Or an engineering subnet may have fewer restrictions.

The filtering router allows users to access services such as Telnet and FTP while restricting those services’ use of the Internet to access the Intranet.

It can also be used to prevent internal users from accessing restricted data on a local network.

For example, you can allow finance members to explicitly use FTP when denying FTP requests from the engineering department in the finance department.

Some services can also be included in the rules in the filter table by source or destination port number.

A rule can be set that tells the router to examine the source address on each incoming IP header so that if the source address is internal, the router will not support the packet.

What is ADSL Modem Router?

When you purchase a service from any Internet Service Provider, you are given a device, this device is ADSL Modem.

The ADSL Router used for Internet access also has built-in additional components such as a Switch, WiFi.

The router can interact with your ISP to provide Internet access and allow you to surf.

Combined devices hosting multiple services have their advantages, but also downsides. Instead of using two separate devices, the device provided by the ISP can be used.

However, using a single device is not recommended as it will cause performance problems in a large network. For example, a company does not use a single device that performs all tasks. More advanced network devices are preferred instead.

As a result, you can buy your own device instead of choosing the device that is paid by the ISP. Because the performance of these allocated devices is aimed only at home users, it may cause future problems in your developing network topology.

Also, the device provided by your ISP may not have the latest technologies like 802.11ac and 5Ghz Wi-Fi.

Therefore, if you are going to buy an ADSL Modem or Router yourself, you should make sure that it includes the latest technologies.

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