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How to use a router?

To build most IP networks use several types of devices: a switch (hub) and router.Appointment of the first type of devices we have discussed previously, and now we talk about routers. In this article we consider in detail what a router is and what it is used.

As we have said previously, the switches allow you to integrate network devices into a single network segment with a common IP addressing (for example, we have a computer with the address 172.20.20.20/24 and 172.20.20.21/24. We just connected them to switch and they will be able to find each other and form a single network segment).
Combining two PCs using a switch
Combining two PCs using a switch
But what to do in case we have multiple network segments with different addressing (For example, we have an office 1 with addressing 172.20.20.20/24 and office 2 with addressing 192.168.1.0/24)?. In this case, we can't just connect computers to data networks using the switch, as they will not determine the computers on a different network. Here on helps router! A router is a device which is intended to combine network segments. For example, which was discussed by us above, it is necessary to connect office computers 1 to the same switch, and the computers in the office 2 to another switch. Next is to combine the switches with the router.
Association networks using router
Association networks using router
The router has multiple routing network interfaces and each of them is assigned an IP address from the range of the network to which it is connected. For example, in the figure above, the router interface connected to the network 172.20.20.0/24 specifies the IP address 172.20.20.1 and the address for the second interface is 192.168.1.3.







The routers provide the ability of different network segments to communicate with each other through the use of existing routing tables. Routing tables contain information about networks known to the router (in our example 172.20.20.20/24 and 192.168.1.0/24), IP addresses that sent packets to access these networks, and the metric data allow the router to calculate the preferred route to possible destinations. The data in the routing table can be specified in static (network administrator manually enter the router required routes packet) or dynamically updated using routing protocols.

In the next articles we will talk about how to configure routers, and now we'll see how the routers look like. Routers are big in size, expensive and intended for serious tasks. The figure below shows such a router…
A more professional router
A more professional router
A router can be a cheaper - "Soapbox" and be exclusively for home use (such models are commonly used by ISPs to their users).
Router "Soapbox"
Router "Soapbox"
It should be noted that an inexpensive "toys" to combine two devices: a router and a switch. We can draw a block diagram of two devices. It will look like the following:
The structural layout of a typical home router
The end.

  Read this post in Russian / Читать эту статью на русском языке.

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