In this lesson, we're going to cover
four more network device commands,
including show MAC address table, ARP, VLAN, and power.
Let's go ahead and take a look
at the show MAC address table first.
The show MAC address table command
is going to display the MAC address table
on a Cisco switch, and this will provide the mapping
of the MAC addresses to their corresponding ports.
The show MAC address table command can be used
for troubleshooting to help you identify,
which devices are connected on which ports.
When you enter the show MAC address table command,
you're going to get a table displayed
to your screen that will usually include
four basic columns.
The first column will be a BID or VLAN,
which will show the bridge ID or VLAN associated
with that particular device.
The second column will be the MAC address,
which will be the MAC address of the device
connected on that specific switch port.
The third will be the type of connection, and usually,
this is going to be dynamic because
it's going to dynamically read the MAC address
from the card reported by the device
when it connects onto that switch port.
And then the fourth column is going to be the port,
and this will list out the port
being used by the switch, such as FA0/18
if it was on port 18 of your switch.
Next, we're going to take a look
at the show ARP command.
Now the show ARP command is going to be used
to display the ARP table, which is the address
resolution table inside of that device.
This will show you the mapping of IP addresses
to MAC addresses.
This is going to be used to verify the IP addresses
are being correctly mapped to the
MAC addresses on your network,
and you can use this if you suspect
that ARP cache poisoning
or ARP spoofing is occurring on your network,
and you need to validate that to make sure
the right IP addresses are being mapped
to the correct MAC addresses and the type
of connection that's being used.
When you type in the show ARP command and hit enter,
you're going to get a small table
that's going to show up,
which is going to give you the protocol, the address,
the age, the hardware address, the type,
and the interface.
In the first column, we have the protocol.
When it says internet,
this means that we are using the IP or internet protocol.
Second, we have the address,
and this is the layer three type of address,
and usually it's going to be in a dotted decimal notation
if you're using IP version 4, as you can see here.
The next column you have is the age,
and this will show you the minimum age
for this MAC binding.
If it shows a dash, this means there is no minimum age.
The next column we have is the hardware address,
and this is going to be written as three groups
of four hexadecimal digits, each one separated by a dot.
Normally, when you see a MAC address
being written down as a hardware address,
you'll see it written as 12 characters grouped
into two hexadecimal characters each,
and each one being separated by either a dash or a colon.
But when you're using the show ARP command,
you'll see it written as three groups of four hexadecimal
characters each separated by dots.
The next column we have is the type,
and if you see here, it says ARPA, that means that
this is an internet protocol version four type of binding
because we're using the ARPANET notation,
which was the original version of the internet.
And this also says which switch port is being used
for this particular binding,
and in this case we can see it's ethernet 0/0.
The third one we have is known as show VLAN.
Now, the show VLAN command is going to be used
to configure the VLAN settings on a given switch.
Now, it's going to be utilized to segment
your network traffic for improved performance
and security by creating all
of your different VLANs.
When you type in the show VLAN,
you're going to be able to display
the VLAN mappings on your particular device,
and this will be shown in a series
of four columns as well.
When you deal with the four columns,
you're going to have the VLAN number,
you're going to have the name of the VLAN,
you're going to have the status,
and you're going to have the ports.
In the first column, you'll have the VLAN identifier,
which in this case shows one and 10 as my two VLAN.
Then you'll see the VLAN names.
The first one, which is VLAN 1, is the default VLAN,
and that is how it is always set up
on a Cisco device by default,
and I do recommend you change VLAN 1
from being the default into
being something else as your default,
such as VLAN 100, or VLAN 123,
or something like that.
That's harder for an attacker or hacker to guess.
Next, we have the status column,
and this will tell us if the VLAN is active or not.
And then we have the ports associated with that VLAN.
And here you can see the default VLAN
has four ports associated with it,
which is FA0/1/2/3 and /4.
And then we have VLAN 10, which is going to be
our user VLAN, which has three ports associated with it,
FA0/5/6, and /7.
The fourth and final command we're going to talk
about is the show power command.
Now, the show power command is going to be used
to display and configure your power settings,
particularly any devices that support PoE
or power over Ethernet.
By using the power command,
we're going to be able
to manage power distribution and troubleshoot any kind
of power over Ethernet issues that might arise.
When you type in the show power,
you will get a table that shows you the power allocated,
the power used, and the power available per port.
In this example, you can see that I have a couple
of different columns, including the interface,
the admin, the oper, the power, the device,
the class, and the max.
When we deal with interface,
this is going to be the switch port that we're talking
about, such as FA0/1 or FA0/2.
Under admin, you're going to see whether
or not you're in automatic mode,
which here you can see we are both set to auto,
and for the oper, you can see if it's either on or off.
In this case, you can see that the port at FA0/1 is on,
and the port at FA0/2 is off,
which means port one has power
associated with it, but port 2 doesn't.
We can see in the fourth column
that this is a true statement, because we see the power
of 15.4 watts is being shown on port 1,
but we have a power of 0 on port 2
because that port was turned off.
Then we can see a short name for the device
that's connected over PoE, and in this case,
on port 1, we have an IP phone, there's a model 7960,
which is a Cisco IP or voice over IP phone.
If we look down at port 2, you can see NA,
and that's because again, this switch port
is currently off and not providing power to any devices,
so that device can't be turned on,
and reporting itself.
The next column we have is class,
and here you can see which class of PoE we're using,
and in this case, on port 1 we're using class 2,
and on port 2 since it's off,
there is no class, or it is NA.
The final column we have is max,
and this tells us what is the maximum amount of power
that can be supported by this PoE port on the switch,
and in the case of both switch port 1 and 2,
they are both set to a maximum of 15.4 watts.
So, remember, for the exam,
there are four additional network device commands
that you should be aware of,
and these are show MAC address table,
show ARP, show VLAN, and show power.
Show MAC address table is going to display
the MAC address table on a Cisco switch,
which shows the mapping of the MAC addresses
to their corresponding switch ports.
When you use the show ARP command,
you're going to use this to display the ARP table,
which includes the mapping of the IP addresses
to the MAC addresses that are associated
with that switch.
When you use the show VLAN command,
you're going to be able to see the VLAN settings
for a given switch, including the names of the VLANs,
the numbers for the VLANs,
and what ports are associated with each of those VLANs.
And finally, we have the show power command,
which is going to be used to display the power settings,
specifically those that support power over Ethernet,
on a given switch,
and we use this to manage our power distribution,
and troubleshoot any kind of power
over ethernet issues.