Networking Devices
Lets take a look at the common network devices we'll see in networks today. You'll run into many different devices in production networks, but these are the few networking devices that you really need to be familiar with for the CCNA exam.
Bridges
The first device we're going to talk about is the bridge. Bridges are layer 2 devices that break up collision domains but not broadcast domains. Bridges are the least common device we will find in networks today and are mostly used to break up a collision domain. There isn't much emphasis on bridges in the CCNA so just remember that they break up collision domains and not broadcast domains.
Switches
Most networks however will have layer 2 switches. Switches are essentially multi-port bridges. Switches use special hardware called application-specific integrated circuit or ASICs to achieve high speeds while switching. We talked about how switches break up collision domains but not broadcast domains however switches do have a method of breaking up broadcast domains called VLANs. Virtual LANs are special groups of devices that can only communicate with devices in the same group, or devices in groups that have been set up to talk with each other. We'll go more in depth on VLANs in the switching sections.
Hubs
I'm not going to talk much about hubs since they don't do a lot. Hubs are totally unaware of the network around them and have only one job: forward traffic. When a hub receives a traffic it will forward that traffic out every interface except the interface it was received on. It does this because it doesn't know where the traffic is going but it knows that it shouldn't be sent back out the interface it was received on.
Router
Typically you will find a FastEthernet or even GigabitEthernet ports on a router as well as serial ports, these are used for your LAN and WAN connections. The console port on a Cisco router is used to manage the router. Connecting a console cable to the console port gives us access to the CLI of the Cisco router. The auxilary port is typically used to connect to a modem but can be used in a similar fashion as the console port.
Routers are responsible for route selection. A router can take a packet and determine its destination based on its destination IP address and the router will check its routing table for the destination network and forward it accordingly. No other device, except a layer 3 switch which is out of the scope of the CCNA, can check layer 3 information such as IP addressing and therefore are unable to route packets between networks. Routers are also responsible for route filtration and packet switching. We will go the router in greater detail as we progress through the curriculum.
Routers are responsible for route selection. A router can take a packet and determine its destination based on its destination IP address and the router will check its routing table for the destination network and forward it accordingly. No other device, except a layer 3 switch which is out of the scope of the CCNA, can check layer 3 information such as IP addressing and therefore are unable to route packets between networks. Routers are also responsible for route filtration and packet switching. We will go the router in greater detail as we progress through the curriculum.