- [Instructor] Now that we have
our administrative functions on our routers,
let's take a look at the Corp router
and we're gonna go ahead right now
and configure the interfaces.
We have a fastethernet zero zero off of the Corp router.
It's not listed on there, but that's the LAN.
The connection to the San Francisco router
is the 172.16.10.0/30.
So that give us valid hosts of one and two,
broadcasts of three.
Going over to the LA router, we have two serial interfaces,
one in the four subnet, one in the eight.
So we have five and six and nine and 10 are our valid hosts.
Let's go ahead and run out to our Corp router
and configure them, and just one quick note,
I've already configured the San Francisco and LA routers
with IP addresses and enabled their interfaces.
Running over to the Corp router,
we're gonna go ahead and log in.
And I wanna run a command that's very important to you.
Show IP interface brief.
And I shortened it, but very important command.
This gives you all the physical interfaces
that the host* has found, the IP addresses assigned,
how they were assigned, and their status.
Gonna come back to this very important command.
Let's go ahead and run out our LAN interface,
interface fa0/0, fastethernet zero zero.
You can type the whole thing out or use your tab key.
IP address, it's in the 10.10.10 network
and I'm gonna use the first one in the range,
and then enable it.
The command is no shutdown.
I'll use my tab key, just no shut will work.
If you notice, two negatives make a positive, right?
Anyways, and we're gonna see the the syslog pop up.
It should because my interface is connected into a switch,
which means I have carrier detect.
Now had I not had this interface into a switch,
it would have come up and then just gone right back down
because there was no carrier detect.
Let's go ahead and run out to the serial interfaces.
And this is my connection over to San Francisco.
And I'm gonna use the first one in range on this one too.
We're in the 172.16.10.0/30.
So one and two is my valid host.
I already assigned San Francisco to two
so better keep this one one,
And then enable it with my double negative.
Alright, so in this case here, we should wait.
Hopefully the syslog will come up, there we go.
And notice it came up.
If you were in production or in a test environment,
this would not pop up and tell you configure the other side.
Let's go ahead and do a couple other things.
Configure my s0/0/1.
That's my first interface to LA.
And that's in the four subnet.
10.4, so my first valid host is five.
And we should see our syslog come up
and tell me how great my network is running, perfect.
And then interface s0/1/0.
These are our WAN's-
10.9, 'cause its subnet's eight, first on in the range.
And then a no shut.
And we're gonna go ahead and now verify these.
So I've configured all my interfaces and enabled them.
Notice that they all did come up.
Your serial interfaces will not come up at all
until you configure the other side.
So let's get out of this.
And I could stay inside configuration mode
and use the do command.
But I'm gonna do show IP int brief now.
In the show IP interface brief output,
we've a nice command that goes from left to right,
this really nice output where we get the physical interfaces
that the host found for the router,
the IP addresses assigned,
the method, which would be manual, maybe DHCP,
and then status up and up.
Now on the serial interfaces,
we can see that they're up and up
and the status provides clocking to the DTE,
data terminal equipment, which is your router.
The protocol status is up, which is great.
That means I'm talking to the other side.
So that means I'm getting
layer 2 keepalives from either side.
Now this is Cisco proprietary here, guys.
Under status, the up is layer 1, the protocol is layer 2.
Let's go ahead and take a look at that.
So I'm gonna hit Corp here.
I'm gonna say, how do you say this, show controllers.
The show controllers s0/1/1
goes to my San Francisco router.
To the top, the third line down tells me I'm a DTE,
which means I receive clock from a DC.
I'm expecting a CSU/DSU on this type of serial V.35.
Now let's go ahead and look at the other side
which is San Francisco on the other screen here.
Take a quick look.
This is my San Francisco, which I've already configured.
Show IP interface brief, make sure.
Verify my interface.
This is the command.
I love this command, okay.
So on that interface, it's serial 0/1/1 as well.
So we can see the IP address, 172.16.10.2, the other side.
So there's a couple things I can do.
I can ping 172.16.10.1, that's the other side.
I'm definitely working.
But I wanna show you the show controllers s0/1/1.
Compare this to the one above and we can see
we're DCE V.35 with a clock rate of two million.
So why did this work?
I didn't set the clock rate.
An ISR router will automatically detect
if it's a DC interface and set the clock.
You need to be able to understand for the objectives
whether it's DTE or DCE and set it on the DCE side.
Now please understand that
you will never have to do this in production.
This is a non-production connection where I have
a quote unquote WAN crossover cable between the two routers.
Let's take a look at one more command here.
I'll go back up to the Corp router.
Show IP interface brief,
that's my main troubleshooting command.
So I can see my interfaces and their status.
But wait, I can't see their mask.
So I'm gonna type in the command show protocols.
And this one's real nice.
I can see that I'm running IP.
My other option of course is IPv6.
F zero zero, the IP address and the mask.
And I also can see my WAN interfaces
and their status and their mask.
So the command show IP interface brief
and show protocols are your friend.
Use those everyday to troubleshoot
and verify your interfaces.