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I'm chris criacy ccie number one two nine three three and welcome to this combination
ccna c sent and network plus two thousand nine video training session on daynamic routing
protocols. I want to tell you immediately that no matter
what your experience level or your comfort level is with dynamics routing protocols even
if you have no experience in you have a comfort level we've all been there i know exactly
what that was like. There is something in this video dor use hang
in there we're going to be hitting the high points of each one of these protocols and
i have planty of other videos on youtube and the main websites at the brightness dot com
slash tutorial. That will cover some of these protocols for
you in more depth and also of course the network plus certification dot com our network plus
two thousand nine only certification website. The daynamic routing protocols were focusing
on, are the routing information protocol railed EIGRP the enhanced interior gateway routing
protocol. OSPF open shortest path first which sounds
like a great idea and ISIS the intermediate sistem to intermediate system. For your ccna
candidate you're not going to see ISIS on your CCNA exam, thats going to be in your
CCNP study certainly, when you're working on the BLCI exam, but i want everyone watching
the video to know that both OSPF and ISIS are what we call link state protocols.
Before we discuss what the heck that means lat's talk about one kind of route that routers
already know about and that is a directly connected route.
Let's take a look at what i mean by that now. Magnify that just that you can see here, this
particular router and you should be familiar with the symbol when they 3D circles and the
areas on top, that is a router in network documentation and in any of your exam so you
need to know that without being told that this is a router.
You can see that i configured the ethernet 0 and ethernet 1 interfaces with IP adresses
from the major network numbers ten zero zero zero and twenty zero zero zero.
Will the router does not need to be told about the existence of those networks because it
is directly connected to to them oviously we're going to get a lot more routs that net
for hosts to be able to get saved internet based websides, homes in that kind of things,
but again the directly connected router as routs are already going to be known by the
router for those of you working on cisco exams you should know that in your ip routing table
the literacy is going indicate aid directly conected route.
We also have static routes and i'm definitely not bashing static routes
Here are saying they're bad and centainly your CCNA candidate's i need to go watch my
other videos about static routing and the reason is a static grounding mccomb.
Very important to you and real world networking as well as study for the exams but they do
have some drawbacks they don't dynamically adapt to a network change which of course
is what we call static we write it and thats it.
And if the network changes network is down the segment goes up when we need to get to
we've got to go back we're got to change the routing statements ourselves they're not particulary
scalable and for those of you who maybe running into that term for the first time glad i could
be the first one to tell you that you'll be hearing about two million other times turn
your networking studies but it is an appoint term by scalable we mean weekend grow and
if we're using a scalable solution that means it's a solution that we can continue to use
effectively and that includes time efficiently and effectively as the network grows.
With static routing is your network grows it can be difficult just keep adding static
routes make sure everybody can still get to everything they need to get to and again they
require that manual updating to reflect any changes and again that's you and i as the
network admins that's more work for us and frankly we got enough to do swale static routes
convert can come in handy it's not something we want to build our network arround we probably
want to use a dynamic routing protocol and you create these on cisco routers with the
ip route command. Let's talk about the routing information protocol
RIP we have two versions, version one and version two.
Version 2 is generaly prefered when you're using one of the other in real-world networks
ther are several reasons why the main ones being the reversions to supports variable
linked subnet masking and also that refers into multi cast updates
rather than broadcast them and i've seen some net plus 2009 a material out there documentation
out there the talks up reversion to being a broadcast protocol is not as a multi cast
as you'll see that's a very important line. One problem with versions that they're both
sending out full routing tables every 30 secons and that is a lot of overhead because we've
got to keep in mind that everything we do on a router or with a switch has a cost and
i mean cost us a little bit CPU usage little bit of a memory hit little bit of time that
we're losing maybe doing something we don't need to be doing and four routing tables every
thirty seconds of really unnecessary special you have a stable network which hopefully
we do you definitely don't need a full route table to go out every 30 seconds because is
not only that you're sending router have to pack thosde routes and an update packet and
send it out, then the reciver router are still half done parents they are nothing changed
since half a minute ago but that's a little bit of power in a little bit of time that
study is doing something that is really unnecessary, thats why we tend to gravitate for protocols
like OSPF this is a link state protocol as is ISIS and OSPF does not advertise eight
routing table per say it like RIP does when it actually does it advertises the state of
its links, it can understand the speed of a link an make much more informed routing
decisions then RIP cam show you what i mean by that.
In these particular network you can see that we've got two ways to get from router one
to router two. We can go throug router four which involves
two five twelve k links or we can go from router one through router three which involves
tow t one links the issue is that wall OSPF can be made to easly understand the speeds
and will understand many speed a several speeds by the fall depending of what kind of interfaces
RIP is going to see these paths as being equal because al RIP understend is hub channel which
is not a terribly scientific way of deciding which path doubts literally reports a one-half
two hubs.