You'll see the addresses of other servers, including the DNS servers that keep track of all the names of Internet sites so you can type "www. When you've finished looking at the information, click OK. Note: For security reasons, some of the information about this connection to the Internet has been changed.
You should be very careful about giving your computer's information to other people -- with your address and the right tools, an unscrupulous person could, in some circumstances, gain access to your personal information and control your system through a "Trojan Horse" program.
The first and most basic job of the router is to know where to send information addressed to your computer. Just as the mail handler on the other side of the country knows enough to keep a birthday card coming toward you without knowing where your house is, most of the routers that forward an e-mail message to you don't know your computer's MAC address, but they know enough to keep the message flowing.
Routers are programmed to understand the most common network protocols. That means they know the format of the addresses, how many bytes are in the basic package of data sent out over the network, and how to make sure all the packages reach their destination and get reassembled. For the routers that are part of the Internet's main "backbone," this means looking at, and moving on, millions of information packages every second. And simply moving the package along to its destination isn't all that a router will do.
It's just as important, in today's computerized world, that they keep the message flowing by the best possible route. In a modern network, every e-mail message is broken up into small pieces. The pieces are sent individually and reassembled when they're received at their final destination. Because the individual pieces of information are called packets and each packet can be sent along a different path, like a train going through a set of switches, this kind of network is called a packet-switched network.
It means that you don't have to build a dedicated network between you and your friend on the other side of the country. Your e-mail flows over any one of thousands of different routes to get from one computer to the other. Depending on the time of day and day of the week, some parts of the huge public packet-switched network may be busier than others.
When this happens, the routers that make up this system will communicate with one another so that traffic not bound for the crowded area can be sent by less congested network routes. This lets the network function at full capacity without excessively burdening already-busy areas.
You can see, though, how Denial of Service attacks described in the next section , in which people send millions and millions of messages to a particular server, will affect that server and the routers forwarding message to it. As the messages pile up and pieces of the network become congested, more and more routers send out the message that they're busy, and the entire network with all its users can be affected.
If you're using a Microsoft Windows-based system, you can see just how many routers are involved in your Internet traffic by using a program you have on your computer. The program is called Traceroute , and that describes what it does -- it traces the route that a packet of information takes to get from your computer to another computer connected to the Internet. When I did this from my office in Florida, the results looked like this:.
The first number shows how many routers are between your computer and the router shown. In this instance, there were a total of 14 routers involved in the process number 15 is the Howstuffworks. The next three numbers show how long it takes a packet of information to move from your computer to the router shown and back again. Next, in this example, starting with step six, comes the "name" of the router or server.
This is something that helps people looking at the list but is of no importance to the routers and computers as they move traffic along the Internet. Finally, you see the Internet Protocol IP address of each computer or router.
The final picture of this trace route shows that there were 14 routers between the Web server and me and that it took, on average, a little more than 2. You can use Traceroute to see how many routers are between you and any other computer you can name or know the IP address for. It can be interesting to see how many steps are required to get to computers outside your nation.
Since I live in the United States, I decided to see how many routers were between my computer and the Web server for the British Broadcasting Corporation. The result was this:. You can see that it took only one more step to reach a Web server on the other side of the Atlantic Ocean than it did to reach a server two states away! In the first quarter of , there were several attacks on very popular Web sites. Most of these were "Denial of Service" attacks -- attacks that served to prevent regular readers and customers of the sites from getting a response to their requests.
How did someone manage to do this? They did it by flooding the servers, and their attached routers, with requests for information at a rate far too great for the system to handle. Most routers have rules in the configuration table that won't allow millions of requests from the same sending address. If too many requests from one address are received in a short period of time, the router simply discards them without forwarding.
The people responsible for the attacks knew this, so they illicitly planted programs on many different computers. These programs, when triggered, began sending thousands of requests a minute to one or more Web sites. The programs "spoofed" the IP address of the sender, placing a different false IP address on each packet so that the routers' security rules wouldn't be triggered.
When the packet floods were triggered, millions of requests for information began to hit the targeted Web sites. While the servers were being heavily taxed by the requests, the real impact was to the routers just "upstream" from the servers. Suddenly these routers, which were robust but of a size appropriate for normal traffic, were getting the levels of requests normally associated with Internet backbone routers.
They couldn't handle the massive number of packets, and began discarding packets and sending status messages to other routers stating that the connection was full. As these messages cascaded through the routers leading to attacked servers, all paths to the servers were clogged, legitimate traffic couldn't get through the logjam, and the attackers' goals were accomplished.
Web content providers and router companies have placed new rules designed to prevent such an attack in the configuration tables, and the companies and universities whose computers were used to launch the attacks have worked to prevent their systems being used maliciously.
Whether their defenses, or the new attacks designed by criminals, will prevail remains to be seen. In order to handle all the users of even a large private network, millions and millions of traffic packets must be sent at the same time. As explained above, all any host needs to consider for next-hop delivery is the destination IP address. The filtering added by Sanity Checking also looks at the source IP address, in order to drop those packets obviously using a spoofed source address in an attempt to make the destination host trust them.
A router does not necessarily know the location of the claimed source IP address, but if it does, and if the topology makes no sense or is insane based on the interface where the packet arrives compared to the known network location, that packet is dropped. Look at this simple network diagram at right here. We want to set up sanity checking on our border router.
Let's assume that we use the The below table shows packets that do and do not make sense at our border router. To enable it, you would do something like the following in the startup configuration:. IP Routing Logic How do networked hosts route traffic to its destination?
DS3 interfaces on a Cisco series router. Below is the routing table for host1, as displayed on a Linux system:. It makes no sense for a packet from our internal networks to arrive from the outside world! This must be a spoofed packet, so drop it! To be specific, this is ingress filtering since we are applying it to inbound packets. Who knows?
Our border router doesn't know where everything is, but this isn't obviously a lie so accept and forward it. Routers guide the data with various internet protocols and routing tables to find the optimal path for the packets.
Different methods are used for different networks, depending on size and location. But the purpose stays the same; efficient communication between networks.
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RouterFreak is a blog dedicated to professional network engineers. Configuration Tips , Network Fundamentals , Routing. Andreas Grant. Share on facebook. Share on twitter. Share on linkedin. Share on whatsapp. Share on telegram. This article explains what IP routing is and how it works as clearly as possible. Fireplaces, mirrors, and thick walls are just a few common obstacles that block Wi-Fi signals.
Look for a router that has the capability to reach the far corners of your home. Also, look for one that has a mesh network to extend the Wi-Fi capabilities across the home. Router technology has changed over time. Make sure you have a router that uses the latest technology and has updated firmware. It stands for multi-user, multiple-input, multiple-output technology. It allows Wi-Fi routers to communicate with multiple devices simultaneously.
This decreases the wait time and improves network speed. Cybercriminals can penetrate your home network and install malware and viruses in your devices. They work with an arsenal of tools to gain access to your personal and financial information. Having a router that provides network level protection could help protect against cyberattacks at the port of entry.
Look for a router that has built-in security features, like automatic updates, device quarantine, and signed firmware updates. Routers have become a very important part of the connected home. Make sure you buy a router that you can control easily. The latest routers are easy to install and use. Some come with user-friendly apps that help you with guest networks, parental controls, user time limits, and network management.
Whether you are setting up a new router in your home or upgrading an existing one, make sure you get to know all the workings of your new router and if it is designed to meet your needs.
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