Oh my gosh.
So much fun stuff to cover.
I'd like to chat with you in this video--
using this topolgy that we're going to look at here in just
a moment--
about some of the reasons that we would use these control
methods for manipulating the attitude, the brain,
of a single router to make it behave in a unique way,
rather than just following the defaults.
So let's take a look at the topology.
I'll share with you some scenarios and also
a high level overview of some of the tools
we could use to change the attitude of a Cisco router. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
we could use to change the attitude of a Cisco router.
So let's start with this.
Let's imagine that we just threw on routing protocol
A on this entire network.
And let's imagine maybe it's EIGRP or OSPF.
And what we're going to notice is
that the goal of being able to manipulate and control
the attitude of a outer is important
when it doesn't behave the way we want.
See, our goal is to have connectivity
through the network.
And we don't want any loops.
For example, we wouldn't want--
if we had a default route, or wanted a default route
that pointed to R2. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
that pointed to R2.
And R2 had a default route that pointed to R1.
And then if either one of them got a packet
and they didn't know where to send it,
it would just go, "brrrrrrrrrrr"--
I think that's sound it makes--
until the TTL expires.
Then the packet would be killed.
That's not ideal to have a routing loop like that
based on static routes.
So with all those static routes present, if we just had a OSPF,
we might think, well, it's going be great.
Well, OSPF, by default, has an auto-cost reference bandwith
of 100, which means it sees a fast Ethernet
interface as a cost of 1.
And it sees a gigabit interface as a cost of 1.
So, just right out of the gate, we'd WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So, just right out of the gate, we'd
want to do some tuning for the OSPF processes, that's
what we're using, and specify that we
want the auto-cost reference bandwidth certainly
higher than 100, maybe 1,000.
Or if we have, you know, faster links than gig,
we'd also want to make it even bigger
and do that across the board.
But once we have the basic elements in place,
it should be great.
It should be able to identify the best paths to the network.
So as part of the EnCore and this NRC training,
we've taken a look at the individual routing protocols
and how they operate and their metrics.
And that's important, I would say, extremely important. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And that's important, I would say, extremely important.
Before we start manipulating routes and controlling routes,
we'd want to understand how the routing protocols work first
before we try to change their behavior.
So with EIGRP, it's bandwidth and delay, baby.
That's all they-- it's the lowest bandwidth
in the path, which is passed on by the neighbor,
and the sum of the delays.
And that's what they're basing their metric on.
With OSPF, it's cost and using the linked state database.
And it's important to send the defaults of how those protocols
work and their AD's before we start manipulating them.
Because check this out. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Because check this out.
As we go back to this drawing, let's imagine
we put EIGRP on this network.
And then we said, wow, if we look at the loopback
here on R1.
So if we look at the path from R8 to R1,
the worst link in the path is going to be these serials.
So R8 from all three interfaces is going
to have the lowest bandwidth.
And the path being those serial links
because that's what's passed on with the EIGRP.
That's how it works.
And then the sum of the delays would
depend on what the delays were advertised.
So if we went to R8-- WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So if we went to R8--
in fact, let's do this as an exercise.
If we went to R8 and looked at the routing to get to R1,
which path should it use?
Did it use this guy over here, serial 3/1, 3/2, or 4/1?
And the best way to ask it, or the best way to find out,
is just ask it.
Let's do that.
And I just realized I don't have a routing protocol running.
Real quick, let's just do a router EIGRP 2, that's fine.
And we'll do a network 0.0.0.0.
And we are off to the races.
I'll copy that and just plug that WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
I'll copy that and just plug that
into each of these routers.
One of things I love about EIGRP is-- oh my gosh,
how fast is it?
It is so fast.
So by the time I can even paste these in on R8,
if we do a show IP route for 1.1.1.1.
Yeah, it's got equal cost paths routing to 1.1.1.1 that fast.
So if we were to look at this and say,
wow, your next hop is dot 7 and dot 6.
Your traffic share count is 1.
Let's do a show IP route.
Yeah, we have two routes to the 1.1.1.1 network.
And we might look at the topology WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And we might look at the topology
and say, well, you know, what's up with that?
Why isn't it-- if the lowest cost in the path
is the serial links, how come it's not using this right here?
And so it'd be important to first,
before we start manipulating routes,
to understand why it's doing what it's doing.
So in EIGRP and the OSPF content in EnCORE and here in NRC,
we've taken a look at the routing metrics
and how decisions are made and so forth.
And we'd want to first of all understand
what it's doing before we start to manipulate it.
So here are some tools that we could use to manipulate it. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So here are some tools that we could use to manipulate it.
We could go ahead and say, I want to modify the AD,
the administrative distance.
We can specify using the tools of manipulation
on a router, hey, if you learn about this route
off this interface from this neighbor,
go ahead and specify the route for just this set of networks
to a lower AD.
And if you do it, those will be put in the routing table.
AD wins always.
So that's one way to get those specific routes
in the routing table to change its mind from the defaults.
We could also modify the metric. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
We could also modify the metric.
Now, depending on what routing protocol we're using,
it might be cost.
So if it's BGP it would be the attributes, including
the AS path attribute and the weights
and so forth that are involved with the metric for BGP.
But it's important to understand what the basics are
for individual routing protocols like OSPF and EIGRP and BGP.
So that if we want to, we can modify those.
Now, what are some tools that we can use to modify those?
And one of the main tools is called a route map. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And one of the main tools is called a route map.
And with a route map, we can specify, OK,
based on this happening, if this matches
this network, that network, the other network,
I want to go ahead and change, for example,
the administrative distance, or the metric.
And route maps can be applied for incoming routes
that we're learning or routes that we're sending.
It's basically a Swiss Army knife
of setting the parameters.
We could also set a tag.
And you might say, well, Keith, why would we ever set
a tag associated with a route?
Check this out.
Let's imagine that right here. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Let's imagine that right here.
Let's imagine that this is routing protocol A.
And I'll use a different color.
And we have another network, another group of networks,
that are in routing protocol B. Now, this is not a design goal.
Sometimes we have multiple routing protocols
because we have to.
We're using legacy gear or maybe we're running OSPF
and we have some stuff that's still running EIGRP
that we want to work.
The secret is here that this network right here, network 12, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
The secret is here that this network right here, network 12,
which is the link 10.0.12 between R1 and R2,
if we want that network to be seen by routers down here
and be able to reach it, either these guys need default
routes-- that works--
or they need to have that information.
So what we could do is we could redistribute.
And that brings a whole world of challenges
because the metrics--
let's imagine this is routing protocol B. The metrics
for routing protocol A, whether it's OSPF or EIGRP or ISIS,
they are different than the metrics used
by routing protocol B. And so when we do redistribution, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
by routing protocol B. And so when we do redistribution,
we do it on a router that is connected
to both routing domains.
And we simply give the instructions,
please redistribute this routing protocol B into A.
And then we are also going to have the opportunity
at that moment to specify the metrics and the details
for those routes as they come in.
Because check this out, we want fault tolerance-- usually,
companies do.
And so if we have R3 doing mutual redistribution.
And we have R4 doing mutual redistribution from B to A
and from A to B. That's fine, you might think. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and from A to B. That's fine, you might think.
But what if this network, the 12 network, gets--
I'll put this in a different color so we can see it.
Let's imagine the 12 network gets redistributed into routing
protocol B. And then R4 takes that route, the 12 network,
which is in routing protocol B, and redistributes it
into routing protocol A. What's going to happen then?
We're going to have flaps.
If that route is advertised here, then there, then here,
then there, then here, then there, it shows up,
it disappears, that route could be flapping, which is terrible. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
it disappears, that route could be flapping, which is terrible.
And that's when we'd want to use a lot of our controls to make
sure that doesn't happen.
One of those options is tagging it.
Now, there are several options we could
use to solve this problem.
But one is tagging it, where we take
that 12 network when it comes in, we tag it with a number,
like, 777, Vegas.
So we tag it.
And then that route, as it lives here at the 12 network,
we can train R4, hey, listen, when you're
doing your redistribution, we could combine that
with a route map that's looking for that tag.
And we could tell R4, hey, if it has a tag of 777, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And we could tell R4, hey, if it has a tag of 777,
don't bother bringing it in.
So in combination with route maps, and also some other tools
we have, we have a large assortment of lists.
You might say, Keith, what do you mean lists?
We've got ACL's, access controls lists,
which we're not using for, like, filtering traffic
at an interface.
But we could use it as part of a route map to identify networks.
And we can also, with some protocols,
identify a network prefix and who sent it to us.
And use that as part of our identification process.
We also have distribute lists as part of our tool belt. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
We also have distribute lists as part of our tool belt.
And we have prefix lists, which are another amazing tool
to help identify specific routes that we
want to either permit or tag or filter or process differently.
Another option is an offset list.
And some of these do apply based on the routing protocol
you're using.
But an offset list, if we had, like, EIGRP or RIP,
we could go ahead and apply an offset list.
And we could tell R8, listen, when
you're learning about the route from R7, about the 1.1.1.1
network and it comes in here, go ahead and bump that up
with a higher metric, an offset of, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
with a higher metric, an offset of,
like, 50 higher than what it normally should be.
And that way we're influencing the mind
of R8 regarding that route by using manipulation on R8.
So there are a lot of options for manipulating routes.
Some of them depend on which routing protocol we're using.
And there are three basic things that I want you to take away
from this video.
Number one, it's important to first learn
the defaults and behaviors of the individual routing
protocols.
That's why we have so much content regarding that,
regarding EIGRP and OSPF and BGP,
so you can make sure you understand
those defaults first. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
those defaults first.
And then based on the routing protocol or protocols
we're working with, we can then, if we
need to, manipulate inbound and outbound route updates--
modify the distance or the metrics of the cost
and so forth on those routes that will effectively
manipulate the behavior of a router regarding those routes
it receives to prefer or not prefer one route or one path
over another.
So here's what we're going to do.
In the upcoming videos and labs, I
will walk you through a few scenarios
to give you hands-on practice.
So you'll have a first-hand opportunity WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So you'll have a first-hand opportunity
to practice with route maps and prefix lists
and distribute lists and offset lists
and manipulating AD and using route maps.
So you can have a taste of what it feels like
and then get that hands-on practice to help reinforce it.
So all that's coming up as we continue these videos together.
So stay tuned.
And I'll see you in the very next video.
Meanwhile, I hope this has been informative for you.
And I'd like to thank you for viewing.