We've been told once again that brother one can't ping the loopback of a router.
Four And that's true based on our ping test.
Don't believe what you told in networking.
Verify it.
Show IP protocol on router one.
Shows us that we're running OSPF with process ID one show IP route shows us that we aren't learning
any routes through OSPF.
Show IP ospf neighbor shows us that we do have a neighbor relationship with router two, but at the
moment we not learning any routes we can ping router two.
We have an OSPF relationship to router two, but we are not learning any routes.
Let's look at rather to show IP protocols rather to is running OSPF with process ID one.
OSPF is routing for multiple networks.
Show IP interface brief.
So OSPF is enabled on the loopback.
It's enabled on gigabyte 001 and it's enabled on gigabit 000.
Show IP ospf neighbor.
The router has a full neighbor relationship to write a one, but there seems to be a problem with the
neighbor relationship to the strata with this router ID and this IP address.
So do you see a problem already in the output here?
Show IP protocols.
Shows us the protocol information again.
Let's have a look at rather three.
Let's see if this gives you another hint.
Show IP protocols shows us that OSPF is enabled on this router, but based on this output, what's the
problem?
Yes.
Another hint again.
What's the problem?
When you look at the output on router three show IP protocols and rather TOS show IP protocols.
What's the problem here?
Pause the video at this point if you need more time.
Okay.
So OSPF requires that every router have a unique router id.
Notice these two routers have the same router id.
They will not form OSPF neighbor relationships.
If the neighboring router has the same router ID as the local router.
The local rata router two has this router id, but it sees another neighbor with this.
Right.
ID rather three has the same router id and it sees that rather two is also using the same route id so
they will not form a neighbor relationships.
And order to show run.
We see that OSPF is enabled on multiple interfaces, so that looks good.
Show Run.
Here we see that OSPF has manually been configured with a rider ID of 2.2 to 2.2.
OSPF is enabled on individual interfaces, so that looks correct.
But this is not correct.
This router is forming a neighbor relationship with router four.
And can ping the loopback of router four, but it won't form a neighbor relationship with rather two
because it has the same router id.
Rather to selected its rider ID based on the fact that it's got a loopback interface configured with
this IP address.
So that's correct.
It chose the highest IP address of any loopback interface as its router ID here.
The router ID was manually configured.
So I'm going to change that.
And say no.
Rather ID 2.2 to 2.2 show IP protocols.
Root ID is still configured as follows.
So I'm going to use the command clear ip OSPF process and I'm going to clear the OSPF process to get
it to re learn its real ID.
So show IP protocols.
In this example, it's still showing a rather idea of two.
So what I'll do is manually configure a router ID of 3.3 to 3.3.
And notice now that I've done that, the neighbor relationship comes up in packet tracer.
You may have to manually force things and in the exam you may have to do something similar and notice
the router ID is now 3.3 or 3.3 and that's because I manually forced it to be this in the real world.
If you don't configure this and you reset the OSPF process, it will use the highest IP address of any
loopback as the router ID best practice however for the real world is to manually set your router ID
so that it won't change by mistake.
So show ip ospf neighbor here rather.
Relationships are good.
Notice full and full show IP route.
We are learning some routes through OSPF, such as the loopback address of router three.
Hopefully we can ping the loopback address of router three, which we can on router three show IP route.
We are learning addresses such as the loopback of right of one loopback of router two, but we can't
ping the loopback of router four at this point.
So we need to find out what the problem is there because.
Rather one.
Can stall not ping the loopback of router for it can ping the loopback of router two and router three
but not of router four because router four loopback is not being advertised through OSPF.