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The method of using
a static route

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implies that the administrator,
or hopefully the administrator,

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is configuring specific
instructions on the router

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to tell it how to reach, or how
to forward a packet regarding

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a remote network.

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And we're going to leverage
this topology once again

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in our discussion of
three different categories

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of static routes.

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And the three categories
of static routes

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would be specific routes
to remote networks,

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or, we could have
a static route that

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identifies how to reach a
group, or a range of networks.

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Sometimes that's referred to as
a summary of network addresses.

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And then we'd also
have a default route

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that we can configure, which is
kind like saying to the router,

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if you're not sure
how to forward

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a packet to some
network and you don't

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have any other more specific
information, just go ahead

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and do this.

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So let's do examples
of all three,

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regarding specific
remote networks.

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If we had a PC
right here who was

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trying to ping the 10.5.0.55
host down here on network

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10.5.0, the PC, when
it's putting together

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that ping request,
would identify

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that it's locally on 10.1.0,
and that the remote device is

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on 10.5.0, based on
the layer 3 addresses.

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And, as a result, it
would take advantage

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of its default gateway.

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And, at layer 2, would
encode the layer 2 address

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of the default gateway's
interface, at which point

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this PC is hoping that when
the router receives that,

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it can continue to
make that forwarding

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decision in the direction over
here of the 10.5.0 network.

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So, for example, one here.

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A specific route for R1 to get
to the network might look like,

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hey dear Mr. Router, to
get to the 10.5.0 network,

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go ahead and use R2 as the
next hop, the next device

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to forward it to.

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So on this network here,
This is the 10.3.0 network,

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R1's address is 10.3.0.1,
and R2's address is 10.3.0.2.

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So our static route
that we are configuring,

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R1, would say, to get
to the 10.5.0 network,

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go ahead and forward
it to 10.3.0.2,

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which is the IP address right
here on R2's 0/0 interface.

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And if R1 had that information,
it could then forward that

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frame at layer 2 to the Mac
address of router 2, who

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would then receive it,
look at the destination,

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and continue to forward it
to its final destination.

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And that's because
R2 is directly

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connected to the 10.5.0 network,
and knows how to reach it.

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So this is an example
here of a static route

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to a specific network of 10.5.0.

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The second example
of a static route

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might be a range of networks.

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We could tell R1, hey, Mr.
R1, to go ahead and reach

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10.anything.

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Go ahead and use 10.3.0.2
as your next hop.

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So if R1 gets a packet for 10.4,
for example, this static route

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says, hey,
10.anything, I'm going

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to go ahead and forward
that over to R2,

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and it's now R2's
job to continue

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forwarding that packet.

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And the third option right
here is the default route.

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And with the
default route, we'll

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put the example right here
as number three, is basically

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going to say, Mr. R1, if
you have a packet that's

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going to a network
address that you

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don't know how to reach, go
ahead and use this default

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route.

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And the next hop is 10.3.0.2,
because R2 is the only

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other router in our topology.

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And if R2 is also connected
to this big puffy cloud called

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the Internet, It also
is not like likely

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going to know all the
addresses on the Internet,

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but it also has a
default route configured.

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And it says to R2,
if you don't know

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how to reach a remote network,
you go ahead and forward it

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to your Internet service
provider's IP address.

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So these are three
examples of how

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static routes can
be used for a router

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to reach remote networks.

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And I'd like to do a
thought experiment with you

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just for a moment.

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Let's imagine that we configured
all three of these on R1.

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And furthermore, let's imagine
that this PC right here

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has been configured to use
R1 as its default gateway.

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And this PC then does a ping
to 10.5.0.55, this device right

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here.

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The packet is received at R1.

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R1 has a static route
that says, oh, I

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need to forward this
to the next hop of R2,

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so he forwards the packet
over in this direction.

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R2 forwards it down to
the PC at 10.5.0.55,

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and on ethernet, they'll
use ARP along the way

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if they need to learn
layer 2 addresses.

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No problem there.

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So when this PC
replies, it's going

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to reply back to
its default gateway,

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presuming that it's
been configured to use

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R2 as its default gateway.

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And then when R2
gets the packet,

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it's supposed to go back
to the 10.1.0 network.

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What's R2 going to do?

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And the answer is, R2
is going to give up

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at that point, because
it does not know how

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to reach the 10.1.0 network.

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So what we'd also
want to do is train R2

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on how to reach these
other networks over here,

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the 10.1, and 10.2 networks.

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And we can do that using the
same combination of techniques,

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a static route to the
specific networks, or we

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could have a static route
for the range of networks.

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Or, we could tell R2 to
use R1 as a default route,

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and forward any packets that
it doesn't know the network

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destinations of over to R1,
and now it's his problem.

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In this nugget, we
focused on static routes.

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We identified three
different types

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of routes that we could put in,
a route to a specific network,

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a route to a range or
a summary of networks,

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or a third, a default route.

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And all three
provide instructions

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for the router on how to forward
packets for networks that

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are not directly connected.

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I hope this has been
informative for you,

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and I'd like to thank
you for viewing.

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