In this episode I want to do a quick review of a lot of important denizens of our local area network
air go land review.
So what I'd like to do right now is run through a lot of stuff on switches and routers and such that
hopefully you would already know but for complete this let's just go ahead and do a quick review starting
with switches.
So what I have here in front of me is a pretty standard net gear switch.
Now remember switches filter and forward data based on MAC addresses so switches tend to pretty much
work automatically out of the box.
However there are some features that we're going to see on the exam I want to just make sure you know.
So let's go through those.
The first one is the concept of a VPN.
Now normally when I'm talking on this one switch it is one broadcast domain.
So if somebody sends out a broadcast it goes out to every other port.
However if we want to we can actually split up that single broadcast domain into multiple broadcast
domains known as villans.
So in essence what I can do is I can set up a VPN and villans have numbers you do like VLAN one Villiam
too.
You really can't say like Villiam.
Timmy it doesn't work that way.
But then once I create these villans I can then assign ports and in this case I could say I could take
the first this is a 26 port switch I could take the first 12 ports and make it to be really on one and
the rest of the ports be to be there in two and it would be as though I simply had two completely separate
switches.
So to see this what I've got is the configuration screen up so let's take a look over here.
Now this machine is right out of the box.
I have done really no configuration to it whatsoever.
I also need to warn you as there are tons of settings in here that I am not going to be covering in
a quick review we're just going to hit the ones that I want to make sure you're aware of for the exam.
So first of all let's go over to switching now.
If you take a look on this system I'm going to click on Vili's And here you'll see that it has three
built in villans number one which is the default VLAN and then these two others which I doubt I would
ever use.
Voice of the land and audio land.
The reason they're doing that is because it's very common if you're using voice over IP to put all your
voice devices on their own separate VPN and in this case video as well.
Now once you have these villans made and I can make my own villans if I want but let's just stick with
these three for the moment.
What I can now do is begin to assign different ports to different lands.
So I'm going to come over here on this particular machine
and see right here when I click on ports you can see right now they're basically not on any body at
the moment or what we would call untagged.
So if I want to put port 13 on a particular Vili's in this case to
I'm going to go ahead
hope there it is hit apply.
And I now have put port 13 onto the second Vili's LAN The important thing you need to understand it
villans is that the moment I put that port 13 onto a separate Villalon it will be as though it disappeared
from the switch.
The only way I could get other people to talk to it is if I put more ports onto that same plan.
So villans are absolutely critical tool.
It is the way we do what we call layer 2 separation of networks and it's an important security feature.
Now the other security feature I want to talk about is flood gardi Now one of the dangers with switches
is that you can accidentally plug them together in such a way that you can create loops or what we call
bridge loops.
Now a bridge loop will basically knock a network down instantaneously.
So what we've developed with any good switch is something called spanning tree protocol or as t.p.
So the nice part about the PC pretty much just have to turn it on and let's go back in here and let's
make sure SEPs even lit up on these guys.
So in this particular one there's a little tab for SDP.
And as I look here right now SDP is disabled so I'm going to go ahead and turn that on.
Now there's SCDP and then rapid SDP and we pretty much just use Rapide SDP and then PDU flooding is
just if we moved boxes around it knows how to track that type of stuff.
So really all I need to do in this particular case is make sure that this guy is turned on.
So those are the two big things about switches I want to make sure that you're aware of.
Number one this is where we set up the lands and then number two make sure that you're comfortable with
the concept of SCDP and that it prevents loop floods.
So that's a very very good thing.
So let's go and do this one more time except this time let me replace this with a router
it switches filter and forward based on mac address or Layer 2 routers filtered forward based on IP
address or Layer 3.
So the term layer 3 switch is a very common term that can be used interchangeably with the word router.
So if routers filter and forward based on IP addresses routers are going to act as the doorway or the
interface between different network IDs.
So let's take a look at this.
So here's a router that I have right now.
And in this particular case this simple router is separating two different network IDs on one side is
192 168 for.
And we'll just put that 0 can there.
Lots of computers in there.
So it'll be 190 168.
Forgot one for the router itself that 2.3 for whatever.
And then on the other side it's going to be 10 11 12 0 so the router itself spans and filters and forwards
IP addresses between these two different network IDs.
Now don't think routers can only do two.
For example let's do this again except this time let's span three different network IDs so here's a
router that's separating three different network IDs routers can have lots and lots of different interfaces
in them.
Anyway let's go back to our original drawing now if a router is acting is what we call a gateway it
is acting as the interface between your local area network and the big Internet of the cell so we call
that a gateway router a gateway router will always be running the network address translation or nat.
In that case our Internet service provider gives one IP address to the router and then the router converts
that into a private IP address range which then passes out to the individual computers on the local
area network.
Now since this router is already connected to the internet it is very common for us to do something
called a firewall.
A firewall is a piece of software that is commonly run on a gateway router which protects us from the
evils of the Internet so it can forward and filter based on port numbers based on IP addresses your
Else all kinds of different stuff.
So we would call this a network firewall because the gateway is running the firewall software and protecting
us from the evil of the Internet.
So this was a quick and dirty review of some of the terms that you're going to be seeing on the exam.
I hope you're familiar with all these terms and can appreciate that I'm doing a very light touch to
it.
However if there are any terms that I just brought up that you're unaware of I wouldn't think it would
be too bad of idea to consider for example my network plus video series to help you dial in and make
sure you really understand what these switches and routers really do.