This is one of multiple OSPF troubleshooting videos.
In this scenario we've been told that router one is not able to ping router four so let's test that
can write a one ping.
The loopback of rotter for answer is no show IP route we are receiving OSPF root, so we receiving a
route for the loopback of router two.
We're receiving a route for Network ten 1 to 0, but we're not receiving other routes.
Show IP ospf neighbor confirms that we have a neighbor relationship to router two.
So as an example, we can ping the loopback of router to all disable IP domain lookup to make trace
root complete quicker.
And let's see if we can trace to router four.
The trace in this example will not leave the local router.
Because we don't have a gateway of last resort and we don't have a specific route to quadruple for.
So the trace is simply dropped at the local router.
Now what about rather to show ip ospf neighbor rather to has a neighbor relationship to router one but
doesn't have a neighbor relationship to router three.
Ken brought a two ping.
Rather three.
Yes, it can.
So it doesn't look like it's an IP connectivity problem.
It looks like it's something else.
Ken writer three ping rather two.
Yes, it can show.
IP ospf neighbor.
Writer three has a neighbor relationship to write of four but not to router two.
So we definitely have a problem between writer two and writer three.
So in order to show IP OSPF interface brief, OSPF is enabled.
And gigabit is zero zero and gigabit zero one shows.
CDP Neighbours shows us that router three is connected to gigabit zero one.
So OSPF is enabled on that interface.
The local route is a designated router.
Back on road a three show IP OSPF interface brief OSPF is enabled on gigabit zero zero and gigabit zero
one.
We can see that router two is connected to gigabit zero one.
So OSPF is enabled on this interface and the local router believes that it's the designated router.
So we have two routers.
On the same segment thinking that they are the designated writers.
Let's have a look at the interface without brief.
So show IP OSPF interface gigabit zero one.
We can see the IP address of the router.
The area is area zero.
Router ID is this network.
Top is broadcast.
Cost is one.
There's no backup designated router on the segment.
We can see the hollow and other timers.
We can see a lot of other information here.
What about on this side?
So show IP OSPF interface gigabit zero one.
Can you spot the problem?
What's the problem between rather two?
And rather three.
He has rather two years, rather three.
What's the problem?
Okay.
Look at the timers for OSPF to form neighbor relationships, the timers must be the same.
The hollow timer on router three is 30 seconds, whereas it's 10 seconds on router two.
Date interval on the site is 40.
The site is 120.
Wait is 40, 120.
Returns RETRANSMIT is five and five.
Also have a look at the network type.
That's a broadcast.
This is a non broadcast.
If you want OSPF routers to form a neighbor relationship, the timers need to be the same.
Timers can be influenced by the network command.
Ethernet is a broadcast multi axis environment, not a non broadcast environment that would be used.
For free relay as an example.
So we need to set the OSPF network type to broadcast and notice.
As soon as I've done that, neighbor relationships are formed.
If you look at the timers.
Notice the timers here are now the same.
As rather two timers are set the same.
Show IP ospf neighbors.
We have two neighbor relationships, so back on router one.
It's rather one able to trace to quadruple four.
Yes, it is.
So that looks a lot better.
So we can ping quadruple for as an example.
That was an OSPF troubleshooting scenario.
Make sure that your timers are the same.
Check your network types in OSPF.
It's important that the OSPF network types be the same for CNA.
There are some weird and wonderful implementations that you can have with OSPF, but that's not important
for CNA.
Check your network types, check your timers, ensure that they the same between writers.
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