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Lesson 5Switches, bridges, and routers
ObjectiveDescribe switches, bridges, and routers.

What are switches, bridges, and routers?

Switches, bridges, and routers are products used to interconnect LANs, WANs, and networks of different types.
LAN and WAN solutions have evolved to the point where they have become almost like packaged applications. They are easy to install and reliable in terms of operation (except for the always-challenging wiring question).
Switches, bridges, and router vendors
Interconnection, or how to get all the disparate networks to talk to one another, is the domain of the network and e-Commerce architect. Switching, bridging and routing are the primary interconnection tools of the network architect.

Switches and bridges Routers
These products support low-level data internetworking functions, such as compensating for speed differences between different networks, and filtering, forwarding and converting packet information. Switches are hardware-based, and thus tend to be faster than software-based bridges. Offer similar functions to switches and bridges, in terms of forwarding packets; however, they also perform address and directory mapping and resolution, an absolutely essential function in the enormous Internet, or in large VPNs. Routing occurs as OSI layer 3 (the network layer) rather than OSI layer 2 (data link layer), which is where bridging and switching occurs.

Considerations for bridges, switches, and routers


A bridge goes one step up on a hub in that it looks at the destination of the packet before sending. If the destination address is not on the other side of the bridge it will not transmit the data. A bridge only has one incoming and one outgoing port. To build on the email analogy above, the bridge is allowed to decide if the message should continue on.
Bridges are typically used to separate parts of a network that do not need to communicate regularly, but still need to be connected.

Traffic Handling in an X.25 Network
Traffic Handling in an X.25 Network


A switch steps up on a bridge in that it has multiple ports. When a packet comes through a switch it is read to determine which computer to send the data to. This leads to increased efficiency in that packets are not going to computers that do not require them. Now the email analogy has multiple people able to send email to multiple users. The switch can decide where to send the mail based on the address. Most large networks use switches rather than hubs to connect computers within the same subnet.


A router is similar in a switch in that it forwards packets based on address. But, instead of the MAC address that a switch uses, a router can use the IP address. This allows the network to go across different protocols. The most common home use for routers is to share a broadband internet connection. The router has a public IP address and that address is shared with the network. When data comes through the router it is forwarded to the correct computer. This comparison to email gets a little off base. This would be similar to the router being able to receive a packet as email and sending it to the user as a fax.

LAN Networking - Quiz

Verify your understanding of the concepts we have covered with a lan networking quiz. This quiz will provide you with valuable practice prior to taking the end of course test.
Lan Networking - Quiz