Instructor: In this lesson,
we are going to talk about limited connectivity issues.
Now, limited connectivity is a specialized message
that you're going to receive within your operating system.
Generally, when you get a limited connectivity message
this means that you have a physical connection
to the network established,
but you have not gotten a proper lease from the DHCP server,
and therefore you can't make it out to the larger internet
in order to interact with those services.
Now, generally, if you have limited connectivity,
this means you have received what's called an APIPA address,
which is the automatic IP addressing or APIPA.
Now, any address
that starts with 169.254 dot something, dot something
is considered an APIPA address.
These APIPA addresses, or automatic IP addressing,
is assigned by Windows, Mac, or Linux
to your network interface card,
so it has some kind of IP address.
But it's not one that's valid for routing on the internet.
So if you have an APIPA address,
or something that starts
with 169.254 dot something, dot something,
this means you can connect to your local area network
but you're not going to be able to connect
out to the larger internet.
Now, in addition to using these APIPA addresses,
some Linux servers and hosts
will instead set their IP address to 0.0.0.0,
if they can't get a valid IP address from the DHCP server,
so keep that in mind as well.
But on Windows, Mac, and most Linux machines,
you will see an address starting
with 169.254 dot something, dot something
as your APIPA address.
So what do you do if you're in this situation
where you have limited connectivity?
Well, there's three main things you need to check.
First, you need to figure out if this issue is affecting
just one network client or many network clients.
When you're getting an APIPA address,
it could be just an issue
with your particular network client,
or it could be affecting everyone on the network
because the DHCP server is down.
Once you've identified if it's just one client
or all of your network clients,
you'll be able to better troubleshoot the issue.
If it's just one client, then you want to verify
that you have the proper configuration
of your patch cords
going from the computer to the wall outlet,
or that you're properly connected to your wireless network
using the proper SSID and password
for that wireless network.
Once you validated that,
you also want to ping the DHCP server
and verify that it's online
and giving out valid IP addresses.
Now, if your single client is still having an issue,
and the DHCP server is up
and you've checked your patch cords
and your connections are valid,
then you want to check if your VLAN is properly configured.
Some switches use VLANs
and put people into different subnetworks
as a way of increasing security,
but if they haven't properly configured those VLANs,
it can actually block DHCP traffic
and therefore your client will not get a DHCP address
when connected through that VLAN.
Now, on the other hand,
if this issue affects lots of different clients,
then it's most likely not a setting that's incorrect
on your particular system,
and instead it's going to be an issue with the DHCP server.
This could be that the DHCP server is offline,
has an invalid connection to the network,
or it's simply run out of available IPs
to hand out using leases.
When this happens, you're going to need to increase
the amount of leases inside of the DHCP scope,
or you need to go through each of those IPs
that have been handed out
and validate that everyone is still online and connected
and still needs those leases.
If they don't, you can release those leases
from the DHCP server in order to free them up,
add them back into the scope,
and hand them out to the other systems
that are trying to connect to the network.
So remember, when you have a limited connectivity issue,
normally this means you're having a DHCP issue,
and you're not able to get a dynamic assignment
that includes the IP address, the subnet,
the default gateway, and the DNS server's IPs
that your system needs to use.
If this is the issue,
you're going to need to troubleshoot either the DHCP server
or your connection to that DHCP server.
In addition to this,
you could statically assign
those four pieces of information that you need,
such as the IP address, the subnet, the default gateway,
and the DNS server's IPs,
instead of using DHCP,
if you can't make the connection to the DHCP server,
and this could restore your limited connectivity
to full connectivity.