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Network Devices

Example of network devices commonly found in today’s LANs..

Hub / Switch / Router / Repeater / Firewall

Hub:

Also refer as duffer device as by default it send. Hub work on OSI Layer 1. Its obsolete now's a day. Hubs have numerous disadvantages. They are not aware of the traffic that passes through them. They create only one large collision domain. A hub typically operates in half duplex. Also having a security issue with hubs since the traffic is forwarded to all ports and capture all traffic on a network with a network sniffer!

Switch

Switch is also called a Intelligence device, which only sends signals only to a specific device as it not broadcast to every device over the network. Switch operates at 2nd layer of OSI model.

Routers

Router is a networking device that routes the packets over the network. One network to another Network. It operate on OSI Layer 3. Routers generally divide broadcast domains and have traffic filtering capabilities.

Repeater

It regenerates the weak signal weak signal and forward it to destination device with the maximum output as generated.

How routers work

A router uses IP addresses to figure out where to send IP packets. When two hosts from different networks want to communicate, they need a router between them them to share or route packets

For example, consider the following example network:


 

Computer A and Computer B are on two different networks. If Computer A wants to communicate with Computer B, will have to send a packet to the router first. Then router receives the packet from Computer A and checks the destination IP address. If the destination IP address of Computer B is in the routing table, the only router will forward the packet out to Computer B that received from Computer A interface associated with that network.

What is a routing table

Routing table lists a route of every network that a router can reach within. Can be statically configured or dynamically. Routing table is use by the router when deciding where to forward packets.

The picture below shows how a routing table looks is:-

Command to display an IP routing table that shows ip route.: ip route

 

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