In this video we are trouble shooting network connectivity problems.
We've been told in this scenario that one which is a viral router running ingenius three is not able
to ping the loopback of viral rodded T with the loopback of quadruple fall.
And that's true.
Show IP brought shows us that we only have a connected and local network in the writing table show IP
protocols shows us that we are running the P.F. rotting protocol and it's enabled on all interfaces
on the router show IP OSPF neighbor shows us that we have a full relationship with a neighboring router
with IP address 10 1 to 1 which is this Rotto 1 Rodda so on brought a one show IP always.
NEIGHBOR We only have a neighbor relationship to tend up one but wondered one the on the left that's
on interface first.
Ethan It was 0 0 0 IP protocols OSPF is enabled on the router and is enabled on all interfaces so IP
OSPF interface brief we have SPF enabled on the serial interface and the Fosset Ethan an interface can
you see the problem.
Notice the state of the serial interface is down.
So show IP interface brief we can see that the serial interface is up or down.
Something wrong with the serial interface.
So run interface serial to slash a 0.
Shows us that an IP address is configured on the serial interface but the interface is no shut.
In other words it's of up.
Nothing else is shown.
So show interface serial to slash zero.
We can see that the interfaces up down we can see the encapsulation keepalive is set to 10 seconds
to show IP was P.F. interface brief we can see once again that OSPF is enabled on the serial interface
but the neighbor relationship is down show IP interface brief interface is up or down.
So this interface has not been administratively shut down show interface Ciril to slash zero.
Can you see the problem.
What's wrong in this output.
Notice here and kept solution HGL see on the side encapsulation Peepy show run interface to slash zero.
We can see that the site has been set to use peepin kept solution.
So we need to either set it to use HGL C which is the default on Cisco serial interfaces or we need
to set the encapsulation to people on both sides so set the encapsulation to H.M.S. show IP interface
brief
interfaces up and down but notice that schist come up and notice the OSPF relationship has gone to full
so on a one show IP SPF neighbor notice we now have two neighbor relationships one two Rodda two across
the several interface and one to this Iowas Virata on the left using the fast ethernet interface.
So that looks a lot better.
Let's have a look at the writing table of Rotto one which is viral.
I was Virata.
We now see the loopback quadruple for the writing table.
So can we paying that loop back.
Yes we can.
We're going to disable IP domain look up to speed up tracing So Trace could fall.
The trace shows us the path that goes to the Strutter one with the search interface to write it to with
a serial interface and then on to the I was the router with the loopback quadruple for now to prove
that I could do a debug a debug IP ICMP to ping and notice we see the output on the screen of this Rodda.
So be careful when asked to troubleshoot a broadening protocol such as I was P.F. in the CCN exam.
The issue could be unrelated to OSPF the issue could be an interface that's been mis configured in this
example the encapsulation was incorrect.
You have to have either HPLC on both sides or PDP on both sides of a serial link.
A mismatch caused the interface to go up or down.
In other words the interface was administratively up but the line protocol was down which caused an
issue with broad exchange and advertisement which meant that we couldn't send traffic from the left
hand side of the network to the right hand side of the network.
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