How do routers work? I'm starting this series to show the basics of network routers and what they
do, how they function, and what you need to know about them to pass the Network+ level Exam. So
in this first video we answer the question of "How do routers work?" When you have data requests on a
computer network, those requests (that traffic or data being sent over the network) are destined for
one of two locations: Either for a destination device inside your network or a destination
device outside your network. In our series on Switches we looked at how Layer 2 and Multi-layer
Switches move data really efficiently inside your network, typically a LAN (a local area network),
but they aren't capable of moving data and traffic outside the network. That job is for something
like a Layer 3 switch or more commonly the Router. So in this short video I'm going to show
you the concepts and fundamentals of Routers and routing. When we have data on a computer, printer,
or any network device, that needs to be sent to another device outside your Local Area Network,
LAN devices aren't what we need. Again, typically LAN devices are Layer 2 switches as they look at
MAC addresses (Destination and Source) in the actual frames of the data to determine where
that data originated from and to where it needs to be sent. But switches don't look at Layer 3
data (which is the Source and Destination IP addresses). Routers were developed for just such a
purpose. So really quickly before we get into what a Router does and the basics of how it functions,
I wanted to show you the typical diagram symbol for the Router. You've seen it in other videos and
with others who teach networking but when you see this cylindrical disk shape with the four
arrows on top (two pointing at each other and two away, or sometimes all four arrows are pointing
outward like this) this represents a network Router. In real life a Router looks more like
a Switch. This is an actual picture of a Router. Now even though a Router looks like a Switch,
its functionality is totally different and in most cases you'll find that a Router has fewer
external ports or connections available for use than a Switch will (not always but 9 times out
of 10). This is because Routers route traffic between networks LANs and don't need to connect
as many devices as possible like a Switch will. If you haven't watched this video showing the
intro to frames, packets and headers, I highly recommend it as it shows how the packet is built
into the Layer 2 frame for data to be sent out on a network by a sending device (a PC,
a printer, a server, etc.). So getting back to the functionality of a Router, you'll recall in
our series on Layer 2 Switches that the Layer 2 Switch looks at the Source and Destination MAC
addresses on the front of a frame. Well, the Layer 3 switch or the Router actually looks at the
Source IP address and the Destination IP address in the actual PACKET headers to determine to which
network the data needs to be sent (either this LAN local area network or another network OUTSIDE this
network). So here's where I use the reference that a lot of authors and instructors use...the postal
service. If you mail a letter in snail mail as we call it these days and it's going to another city,
state or country, you wouldn't expect your local postal delivery person to personally
deliver it all that way. After all, they only know their personal route that they deliver to
each and every day. If your local postal delivery person gets a letter from you that needs to go to
another city state or country, they take it to the local post office to have it connect up with other
long distance carriers to have them deliver it to that more distant location. Using this example,
your Layer 2 Switch or Switches can be viewed kind of like your local postal delivery person
delivering data within packets and frames to local devices within a LAN.
The Router can be viewed like the post office determining that the destination IP address
within the packet portion of the traffic is outside of this local area network, and
then doing what it needs to do to ship it out to connections or to the next hop (we call it) to get
it to that outside location or network. Now in the upcoming videos in this series on routers
i'm going to get into a little more detail about how routers do this as well as how
they learn existing routes from each other, so thank you for watching this video! Make
sure to like and comment on this video if you enjoyed it and i'll see you in the next video!