Once a network has a dozen or so routes,
it's no longer reasonable and is kind of
tedious, actually, to do manual configuration of static routes.
So we're going to migrate or move
to something more flexible.
Specifically, dynamic routing protocols.
So in this topology, I've taken the liberty
of adding an additional router, router 3 and also
some additional networks.
So we've got the 10.1.0, 10.2.0, 10.3.0, 10.4.0, 10.5.0,
also 10.6.0 between R1 and R3, 10.7.0 between R3 and R2,
and the 10.8.0 network hanging off of R3.
And the benefit of using a dynamic routing protocol
is we can get these devices talking
to each other to dynamically share information regarding
what routes are reachable and through whom.
And there's two major camps regarding
dynamic routing protocols.
There's distance vector.
The classic example of that would be the RIP protocol--
may it rest in peace.
It stands for Routing Information Protocol.
And there's a couple flavors of it.
There's version 1, and there's version 2.
Most people are using version 2, if they're still using it.
And with a distance vector routing protocol,
it's routing by rumor.
What do you mean, Keith, routing by rumor?
Well, if R1 believes that he can reach the 10.1 network and 10.2
network, he's going to go ahead and tell R2.
And R2 says, great, thanks for the information.
If I need to reach those networks or forward
packets in those directions, I know
I can use you as the next hop.
And R2 can propagate that information to other router.
So R2 can advertise to R3 the networks of 10.1.0 and 10.2.0,
even though he doesn't have firsthand knowledge
of those networks, he simply heard about them from R1.
Another approach with dynamic routing protocols
is link state routing protocols.
And with link state routing protocols,
we still have routers that are directly connected to networks
except those routers advertised the states,
the details regarding the networks
that they're connected to.
In one of the protocols, called OSPF,
which is a very good example of a link state routing protocol--
OSPF is an acronym for Open Shortest Path First--
and with OSPF, the routers are going
to send that little LSAs--
link state advertisements.
In that way, R2 can take a look at the link state
advertisements from R1 along with link state advertisements
from everybody else.
And then every router, based on all that data,
can make their own calculations about the best way
to get through the network.
So we're not relying so much on rumor from a neighbor regarding
everything behind that neighbor, a link state routing protocol
is like OSPFR, more tight more concise and more accurate
and usually, they converge faster.
That means if there's a change in the network,
the entire network will figure it out
much faster than in a distance vector routing protocol.
And then we also have some protocols
in this group called hybrid.
Now Cisco, a long time ago, created a routing protocol
called EIGRP.
And if you read Cisco's documentation,
they're going to tell you, it's an advanced distance vector
routing protocol.
Because it uses all of the features of a distance vector
routing protocol, but EIGRP also uses
mechanisms that are similar to how a link state operates.
So it can be referred to as an advanced distance vector
or if you wanted to call it a hybrid,
no one's really going to look twice if you put it
in either of those categories.
And one of the features of link state that EIGRP does use,
they form like an official neighborship--
using that routing protocol with their neighbors.
And that way if something changes,
they can have very quick information
about changing the topology and updating their routing table
to reflect the correct routing tables through the network.
And one other protocol I want to talk about here
is BGP, the Border Gateway Protocol.
And that's the protocol that we use on the internet today.
And one interesting thing about BGP is that BGP neighbors--
two BGP speakers that are talking to each other--
they don't have to be directly connected
or on the same network.
So for example, we can have a router over here.
Let's call it router 4.
And up here, we can have router 5.
And as long as they have reachability--
meaning they have connectivity to each other through
the network--
they can establish a BGP neighborship,
which makes it fairly unique compared
to distance vector or a link state routing protocols.
So we can put BGP if we wanted to also in that category called
hybrid because it has some mechanisms that resemble
distance vector protocols, and it also
has things like neighborships that are similar to how
link state protocols operate.
And the benefit of using a dynamic routing protocol is
that once we have configured the dynamic routing protocol,
changes that are made on the network--
links coming up or links going down or new networks being
added--
all that information can be dynamically communicated
to the other routers, so we don't
have to manually configure static routes.
In this Nugget, we took a look at some
of the categories and benefits of dynamic routing protocols.
I hope this has been informative for you,
and I'd like to thank you for viewing.