This is one of multiple Ethernet trouble shooting videos in this typology.
We've been told that to write one on the top left is not able to ping some of the other routers in the
topology so let's verify that on right of one show IP interface brief IP address of Rodda one is 10
to 1 and 1 to one to IP address is 10 1 to 1 and 2.
So from Router one can be paying Rodda to pings or failing Let's confirm the IP address information
so show IP interface gigabit 0 0 IP addresses 10 1 1 to slice 24.
Let's do the same over here.
Make sure that the subnet mask is correct IP address is 10 1 1 1 slice 24 the side it's 10 1 1 2 slice
24.
So that looks good.
Doesn't look like they'll be any other reason why we can't ping to rot it too.
What we'll do is do a debug IP packet.
Be careful doing these commands in the real world.
You may have to use an access list on that debug.
Otherwise you could kill your Rodda with the amount of output that's generated.
OK so we see messages such as sending full packet.
So it looks like Rato one is forcing the packet out of the net interface onto the network to debug IP
packet on the side.
What I'll do now is repeat one ping only so I only send one packet onto the network.
It doesn't look like anything's arriving on the site.
If you can use why a shock to help you capture traffic someone to capture traffic between the switch
and router to and to that ping again.
But I don't see any ICMP traffic in shock.
We see spending information but we don't see any other information in why shark we see for instance
a loop from a device with a MAC address.
We see some spending tree we don't see any of the traffic
so let's see if the traffic is actually getting to the switch.
We'll do that ping again.
OK so this the ICMP message sent from brought a one to router to the fact that we see ICMP means that
the router has learnt the MAC address of router to its MAC address is zeroes ending in one destination
MAC address is zeroes ending in a two.
So it looks like up worked.
But the pings are failing.
Let's confirm the MAC address on router 1 MAC address is set to this point in MAC addresses this to
the MAC address has been changed to that value.
What about on rodded to MAC addresses this burnt in MAC addresses that.
So it looks like the traffic from Router one to router to get sent on this link but doesn't arrive at
route to what I'll do is do a broadcast.
Again you need to be careful with doing this kind of stuff in the real world.
Because this is a lab I'm going to show you various options.
So I notice when I send a broadcast traffic it does arrive at route too.
So let me on all that and only do a D-bag IP ICMP not a debug package because that generates a lot of
traffic on all over here.
In other words turn off all debugging and only send one broadcast.
So the broadcast gets to rodded to say here we got a reply to the broadcast it looks like but it doesn't
look like unicast traffic works in the network.
So broadcast he sent it gets to write it too.
But a unique cost doesn't seem to get to rodded too.
So let's have a look at that switch and see if there's a problem on the switch.
So on the switch shows mac address table.
OK.
Can you see a problem in the output what looks wrong in the output.
Now this year we've got a static MAC address for MAC address to going out of gigabit.
Two and Three.
But switch to show interface gigabit.
0 shows us that has a MAC address of two.
So this static MAC addresses a problem show run pumping include Mac.
We've got to this entry in the running config which shouldn't be there.
So no I'll paste that in.
So no MAC address show MAC Address table.
Now we only have a dynamic MAC addresses I'll do a ping from Router one to write to that succeeds.
No because the MAC address has been lent properly.
Be careful with static MAC addresses in your MAC address table that will override your dynamic entries
and could send traffic to the wrong port in your typology.
Ok so can we ping rotas 3 which has an IP address of 10 1 1 3.
No we can't show IP interface Gieger But 0 0.
So this is the IP address of router 3 de-bug IP ICMP.
Let's do a ping again.
It doesn't look like the traffic's arriving at Rodda 3.
Let's have a look at the MAC address table.
I don't see a MAC address for router 3 that's paying Router one from router 3.
Look at this output and see if you see a problem.
So show mac address table showed us previously that the MAC address ending in one was connected to Gigabit
to 0 0 on the switch.
In other words over here but now it looks like that MAC addresses on gigabit 0 to this port here.
So do ping from Router one again and let's have a look at the MAC address table.
Notice that MAC address is now shown on gigabit 00 ping is finished so let's do to ping from the side.
Notice the MAC address has moved to Gigabit.
0 2.
So we getting MAC addresses flipping on the switch.
Let's confirm what the MAC address is on these routers.
So show interface could give it a 0 0.
That's the MAC address of router 1.
What does it look like on Route 3.
So show interface.
Gigabit 0 0 this is the Rogers interface.
Notice the MAC address.
The rodders have duplicate MAC addresses.
That's not going to work in an Ethernet environment so let's configure the MAC address as follows.
And let's see if Rotto one can ping wrote three 3 Now notice the ping succeeds and that's because the
devices have different MAC addresses now available on different ports.
Which is correct Prod. diagram Ethernet breaks if you have the same MAC addresses on the same layer
to segment MAC addresses are meant to be unique.
But in the real world you can encounter duplicate MAC addresses check your MAC address tables to see
if MAC addresses a flipping from one port to another.
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