This is one of multiple videos discussing the troubleshooting of Dynamic Host Configuration Protocol
or DHP in this typology.
I've got a U.S. visa router acting as a PC and in Iowa.
Virata acting as a DHP server.
I've also got a router that's simply doing routing from one subnet in the network to another.
We've been told that after the DHB client in the apology he's not receiving an IP address and we need
to troubleshoot the issue.
So let's look at what's going on what Casey has the client show IP interface brief the client is configured
for DHP so gigabit 00 the interface used by the broader to connect to the network is currently up up.
In other words a layer 1 and layer two are working but no IP addresses assigned show run interface gigabit
00 shows us that the interface is configured for DHP.
But once again we are not getting an address assigned.
Let's have a look at it too which is doing interval and writing show IP interface brief we can see that
an IP address is configured on gigabit 00 as well as gigabit 0 1.
Let's have a look at the DHB server.
Show IP interface brief.
This is the IP address of the DHP server.
Can the router paying the DHP server.
Yes it can.
So we can ping from the router to the DHP server show run interface but 00.
Notice this command IP help address.
So that looks that help address is configured to point to the DHP server Let's run a one shot capture
here to see if any DHP messages are being sent to the DHP server.
So I'm capturing on this link.
What I'll do is shut and no shut the interface on the client to get it to request an IP address from
the DHP server that will allow us to see whether the DHP requests are getting to the DHP server.
So NY shock we're seeing a number of DHP messages of full to boot.
P we can see that the router is requesting an IP address on behalf of the client so he has the bootstrap
protocol discover a message client IP address is not configured the relay agent is routed to a show
IP interface brief the Rodda is receiving a DHP discover from the client on this interface and is then
forwarding that to the DHP server.
So we definitely getting DHP discover messages on this link.
Let's do a debug on the DHP service debug IP DHP server.
And let's look at events
force the client to request an address again
OK so something's happening.
Let's stop debugging.
So we're getting a Discover from the client.
So it's definitely being received by the DHP server.
The server is receiving the Discover message but can you see what's wrong in the output.
What's the problem.
Let me give you another hint.
Show IP DHC P pool.
What's the problem.
Can you see the issue in the de-bunk and in the show command OK.
Notice this output we are told that the pool is empty.
Notice this is a problem with the addresses are located
the server is definitely receiving messages.
So we were receiving discovery messages.
There's one address pool available.
OK see if you can see the problem in the running can fake the Rodda.
What's the issue here.
That's IP DHP excluded address 10 1 1 1 to 10 1 1 255.
We've excluded all the addresses from the DHP pool.
So no IP addresses can be allocated to the client.
Show IP DHC pool we have a pool in this range but no addresses are available because we've excluded
them so let's remove the statement
and use the on IPD HGP excluded address 10 1 1 1 2 let's say 10 1 100 show run
extruded addresses are now in this range for the pool notice on the client an address is an assigned
address 101.
So show IP interface brief the client has been allocated an IP address and should hopefully at this
point be able to ping the DHP server which it can be careful with the excluded addresses in the pool.
So show IP DHB P binding.
We now have an address allocated to the client of IP DHP pool.
One address is now least next address to allocate is 10 1 1 1 0 2 noticed previously that the current
index was set to 0.0 0.0.
In other words no addresses would be allocated to clients.
But now the next address that will be allocated is 10 to 1 to 1 2 1 2 2.
So if I change the MAC address on this client to something
like this and then shut the interface down and then no shut it.
What we should see is that the index changes and there you go because the client has been allocated
at this address.
So the next available address is this one.
So that was an example of how to troubleshoot DHP.
I hope you found the video useful if you did please like it please or since I've cried to my YouTube
channel.
I wish you all the very best.