In this example I've got three physical rod is connected as follows.
Rotto one is connected via serial one slash 0 to Rodda two on cereal One solution is zero.
These two rhodos 1841 Cecka Radhe Radhe.
One is connected to a 17:21 using serial zeros.
Zero is zero.
They're using back to back serial cables.
One of the first things you want to do when checking your cabling in a back to back lab environment
like this is using the command show controllers serial and then choosing your interface.
So serial 0 1 0.
Now this come on gives you a lot of output.
You can ignore all of it except the piece that we're interested in over here the shows us that this
interface is a DTV interface.
It's a 35 cable connected to the Rodda.
Clocks are currently detected
on serial 0 slushes 0 0.
So here's the command.
This interface is a DC 35 cable with a clock rate to configure it.
So let's pipe both of those and include 35
is the one interface and there's the other interface.
So notice serial 1 slash is 0 0 is a DTV cable.
So in other words the DTV son or the cable is connected to this interface but a DC cable is connected
to this interface so we'd need to do the clock rate on serial 0 slash is zero on the local router.
But on this interface the clock rate would be configured on the other side so the router to show controllers
serial is 0 1 0 and in the output here you can see that it's a v 35 interface with a clock right now
on the DC side.
So interface serial 0 1 0 0 0 you need to specify the clock rate of the interface.
Now this in the real world would be set by your service provider.
So the telco or PC and provider that you are using which could be AT&T or one of those providers pitch
here because it's a back to back cable we need to set the relevant clock rate and you know some of the
clock rates that we could set some of them seem to face dependent so as an example I'll set the clock
rate to 64 kilobits per second.
This command is in bits per second.
So be careful.
The speed of that command is in bits per second.
Now the router doesn't know the actual speed of an interface.
So if we come on do show run interface serial 0 1 0 we can see the clock rate but show interface serial
1 slash is zero
shows us that this router believes that its physical interface speed is 1.5 four megabits per second.
So in other words T1.
So its important that you set the bandwidth statement correctly for your serial interfaces.
It's not unlike Internet where the interface knows at what speed it's sending traffic and receiving
traffic.
You have to actually configure it so should do show run interface.
Cereal is 0 1 0.
Shows us the clock rate and the bandwidth.
They should obviously match ones in kilobits per second.
Ones in bits per second.
Now the clock rate command is only valid on a DC interface.
So on this site on serial 0 1 0 that interface connected to reality too good a DTV cable.
So if we use the command clock rate 64 thousand noticed we told that the command only applies to DC
interfaces so you can set the clock rate but you have to set the bandwidth of the interface to match
the clock rate that's been configured.
So once again that's typically done by your service provider or DC.
In this example because the DC is on the router so it's configured on that interface.
We need to configure the clock rate on the DC side of the back to about cable but to specify the bandwidth
on both sides.
So bandwidth is configured on the side bandwidth and clock rate are configured on that site on this
interface.
This is the DC and once again we can see that by tapping show controllers serial zero slash there is
zero and what you can see in that output of that command is the DCC the clock rate set here is to make.
So we need to configure that right.
And let's just assume in our example that we're going to set at 256 kilobits per second.
So we need to set back to 56 K and then set the clock rate to fifty six thousand.
So show interface serial 0 0 noticed the bandwidth is 56 kilobits per second make sure that the band
with statement is configured correctly as per the clock rate this command actually sets the physical
speed of the interface.
This command tells routing protocols like a whisper funny-I GOP what the speed of the interface is highly.
Running protocols don't query the clock rate because that may be set by an external DCD device.
So on a one sure SCDP neighbor we can see a neighbor or two on this.
A local interface that is in 1841 and it's using Sariel one slash Zira the 17:21 is connected to a local
Saral interface using Sariel one.
So there should be cereal one and the side is the DTG.
So some things to remember the defaulting cancellation on a serial interface on a Cisco router is HGL
see which we can see over there.
You set the clock rate on the DC side keep alive lives a sent every ten seconds to check that the interfaces
up Chessie to the neighbor who says shows me that I made a mistake in the diagram should be routed to
as shown over there so Ratatouille is connected to the 1841 router.
Here it is.
So show CGP neighbor is connected to a number of devices but thats the one that we interested in it's
several interfaces connected to the serial interface of the 1841 router.
So what I'll do is configure an IP address while we hear
with the relevant mosque and let's do the same on this route and then we will do some tests.
So IP address tend to add 1 to 1 to 1 on the first serial interface and then on serial interface serial
0 1 0 and then on the other end to face 1 9 10 1 to 2 to 1.
So hopefully at this point it should be able to ping the 17:21 which it can and then on the second 1841
Radha get an IP address on and it should be able to ping 10 1 1 1 rather 10 1 on 1 which it can do is
running between those two routers.
The relationship has come up show show IP is P.F. neighbor.
See the full relationship has taken place.
Notice the full relationship.
The shows as a dash because it's a point to point link in this example using HTL see once again show
interface serials 0 0 0
0 0 1 0 notice encapsulation has a deal see on the 17:21
router SPF 1 network and now enable OSPF and all interfaces
can see the relationship here is come up.
So the 17:21 should be able to ping the router show IP who is PEF neighbor.
We can see two full relationships are established and now the 17:21 campaign the second 1841 Rodda.