This is one of multiple videos demonstrating how to troubleshoot issues in preparation for the CCNA
exam.
In this example, we've been told that PC one is not able to ping PC two.
So let's verify that.
Can PC one ping.
PC two.
Notice the you and the dot telling us that it's unreachable.
You means that the traffic is being sent to a router and the router doesn't know where to forward the
traffic.
Let's have a look at the routing table on this router acting as our PC.
Notice in the output we have a default gateway configured.
So can the PC ping the default gateway?
Yes, it can.
So PC one is able to ping router one.
In this topology, I'm using Cisco iOS routers in DNS three.
So rather than trying to set up a physical PC, I'm simply using Cisco iOS V images to act as our PCs.
So on router one.
Let's have a look.
Show IP route.
No routes are being learnt through a routing protocol.
We only see local and connected routes on the router show IP protocols.
OSPF has been enabled as a routing protocol on router one.
A routing protocol would be required to allow rather one to route traffic to this remote network.
So rather two would have to inform router one about that network using a routing protocol of some description.
And in this example, it's OSPF.
On rather to show IP protocols.
OSPF is enabled on this rather show IP route.
It's not learning any routes, however, from router one either.
So looking at this output, are you able to see the problem?
This output should allow you to see where the problem is in this network.
So have you spotted the issue?
Rather one has this rather I'd rather to has this rather id the router ids are the same on both routers
in OSPF rather IDs have to be unique, so show run pipe section OSPF in the output we can see that the
router ID has been configured to 1.1.1.1 show run pipe section OSPF.
The same thing has been configured on router to.
So en route to.
Let's configure the router id as quadruple to notice we're not getting any output when we make changes.
And that's because I disabled logging to the console.
So let me enable logging.
And enable logging this site.
Let's see if we get any output.
So show IPOB.
If neighbour or other neighbour relationship has been established on this side, show ip ospf neighbour
neighbour relationship has been established.
So what I'll do just to show you the problem is I'll set it back to router ID of one and notice we told
that we need to clear the OSPF process.
So clear ip ospf one process.
Notice the neighbor relationship has gone down.
And notice we being told that there's a duplicate router ID and we see that on both sides.
So I purposely disabled logging to the console so that you wouldn't see that.
So before I fix it, this is what the configuration looks like at the moment.
Rather ID is set to 1.1 and 1.1.
So what we should do is change that to quadruple to.
In this case, we didn't have to reset the process because the neighbor relationship hadn't been established
yet.
Notice now the relationship has gone to full.
So we changed the configuration from this to this.
Only difference is rather ID is being changed.
Show IP.
OSPF neighbor.
Neighbor relationship is established on the side.
Neighbor relationship has been established.
If you see output like this, it makes it easy to find where the problem is.
You may not have it that easy in the exam as an example.
You may have to discover where the problem is.
Like I've done here.
So can PC one ping PC two.
Yes, it can.
Let's trace to PC two.
Notice the trace succeeds.
So we've successfully fixed the issue in this network.
I hope you've enjoyed this video.
Please add comments below and let me know if you found this helpful.
Don't forget to subscribe to my YouTube channel for more videos.