So far weve only looked at devices that connect hosts

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So far, we've only looked at devices that connect hosts within a network. However, what if we want to connect two different networks together? To do this we use another connectivity device called a router. Router 6:05-7:31 In this example we have three switches. Essentially, we have three different networks, also called network segments. Let's say one of these computers wants to communicate with the computer on another network. In order to do this, we need a device that is able to manage the flow of data based on the IP address of the data packet instead of the MAC address. This is because MAC addresses are only useful within a single network. The switch here doesn't learn or know about the MAC addresses on any other network. However, a switch does know when to send information to the router to be forwarded. When a switch receives information for an unknown MAC address the information is sent to the router, also called a default gateway. When the router receives this information it looks at the IP address on the recipient and uses it to identify which network to forward the information to. The router on that network then sends the information to the switch and the switch sends the information to the intended computer. In addition to this example, routers are also able to bounce information off multiple routers until it reaches the intended network. For example, if information is addressed to none of these networks here but instead some other network the router would send the information on to another router and another and it would keep bouncing off routers until it reached the intended network. This is essentially how the Internet works. Multiple routers connect multiple networks together allowing communication among all the connected networks. Bridge 7:32-8:13 There's one more device you should be aware of that works on a much smaller scale than a router. A bridge is a connectivity device that joins two network segments together. It does this in a different way than a router. In this example, we have two network segments connected together using a bridge. By using a bridge, these two network segments essentially become one big network. This is different from a routerwhich would create two separate networks. Another thing that a bridge does differently is make forwarding decisions based on the MAC address of the computer instead of the IP address. Bridges learn which MAC addresses are connected on the side of the network and on the other side and makes forwarding decisions accordingly. Summary 8:14-8:27 And that's it for this lesson. In this lesson, we looked at the various components that make up a network infrastructure. We looked at the network medium, which includes cable, fiber, and wirelessand we also looked at the various network connectivity devices that allow communication.
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  • Spring '14
  • Computer network, Local area network, Network topology, Metropolitan area network

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