Okay, so let's complete this lab.
The first step is to verify links using CDP and LLDP.
So on core 1
show CDP neighbors at the moment,
we don't see any neighbors. Show IP interface brief, interfaces are up but no neighbors are displaying
shows CDP, CDP is enabled on the switch.
What about switch 2?
Show CDP
neighbors, notice the problem CDP is not enabled on switch 2. Now in the real world, CDP is enabled on
Cisco devices by default. If it's not enabled use the command CDP run in global config mode. So shows CDP
neighbors now shows us that we don't have any neighbors but we are seeing some output that's different
to what we saw previously.
So what I'll do initially is simply make sure that CDP is enabled on all devices, show CDP neighbors
CDP is not enabled so CDP run. Do something similar on access 2.
Show CDP neighbors not enabled so CDP run access 3
before I enable it let's confirm not enabled CDP run.
Okay, so back on core 1 show CDP neighbors notice we are now seeing our neighbors, so we can confirm that
core 2 is connected to our local interfaces gigabit 1 0 23 and 1 0 24. Core 2 is using
this port gigabit 1 0 23 to connect to our gigabit 1 0 23, core 2 is gigabit 1 0
24 interface is connected to our gigabit 1 0 24 interface, that looks good. Access 1 is connected
via gigabit 1 0 23 to our local interface gigabit 1 0 1.
So that looks good.
Access 2 gigabit 1 0 23
this interface is connected to gigabit 1 0 2 also looks good access 3 gigabit 1 0
23 is connected to our gigabit 1 0 3 interface so that also looks good. So the CDP output
looks correct on core1 CDP doesn't run on servers so we don't see the server in the output.
What about core 2?
So in core 2
show CDP neighbors core 1 looks correct,
access 1 is using gigabit 1 0 24 to connect to our local 1 0 1 interface that looks good.
Access 2 and 3 are doing something similar so that looks good what we aren't seeing here is the router.
So let's check the router.
Show CDP neighbor, CDP is not enabled so CDP run, show CDP neighbor now may take it a while.
Just remember with CDP it sends updates out every 60 seconds so it could take up to 60 seconds for you
to see a neighbor relationship.
So you just need to be patient.
Don't assume there's a problem if you don't see a neighbor immediately wait at least a minute and there
you go we can see the router on core 2.
We can see that it's a router, we can see that it's an ISR.
We can also see that the other switches in the topology are 36 60s, back in the ISR may take it a while.
So I'll come back to that on access 1 show CDP neighbor it's got 2 neighbor relationships, 1 to core 1
1 to core 2.
That looks good, now typically you don't have to do it both ways.
If you see the neighbor relationship on one side you'll see it on the other side.
That's not always true
however when you have multi vendor environments HPE switches as an example will receive CDP messages
but not send it.
So you may wanna check things on both sides.
But remember that when you have multiple vendors or if there's an access list blocking CDP coming in to a
switch you may see it only on one side that looks good.
So access 3 is seeing core 1 and 2 and again back on access 2
we can see core 1 and core 2 so that CDP.
But we're not finished yet
we need to check LLDP.