All language subtitles for Common Network Ports - CompTIA A+ 220-1101 - 2

In our previous video, we talked
about how services have port numbers

that they use so that other devices
can communicate and use those services.

We refer to these as well known
port numbers, because both the server

and the client need to know exactly what
port number they'll use to communicate.

This is not only important for the server
and the client,

but it's also important for any firewalls

that may be in the middle
of that communication.

Firewalls have to decide whether to allow
or disallow this traffic,

and they often make that decision
based on the port number.

As we go through this video,
you'll see that

there are a lot of different port numbers
that you should use,

and if you've never worked

with port numbers before,
this will seem like rote memorization.

But the port numbers themselves

become easier and easier to remember
as you continue to use them.

It's important to know these port numbers

and what protocols are often
used by a particular port number.

But it's also important to know
when you would use these protocols.

For example, your exam might ask you
what port number is used by an application

that transfers data in a particular way
across the network.

Let's start

our conversation of port numbers
with FTP or the File Transfer Protocol.

As the name implies,

this is a protocol that transfers files
from one device to another.

There are two port numbers used by FTP.

One is TCP port 20.

This is for data
transfers and TCP port 21,

which is used to control the data
transfer.

FTP is a generic way to transfer data
between devices, but it commonly requires

some type of authentication
to log in to that remote device.

So you might use a username and password,
although some systems will allow you

to log in as anonymous
and use any password to gain access.

The FTP protocol

also includes

a number of file management functions,
so when you connect to an FTP server,

you can list all of the files
on that server.

You can add, delete, rename and perform
other file management

functions, all by using FTP.

There may be times when

you need to connect to a remote device
through a terminal or command line.

Front end.

It's common to use secure shell or SSH

to provide this terminal connection
to a remote device.

SSH commonly communicates
over TCP using port 22,

and it has this text based front end
to be able to access that remote device.

Although we see plain text on our screen,
any communication

sent over
the network is sent as encrypted data.

That's where the secure comes from.

In the name Secure Shell.

There's another way to connect

to a remote device using this text
based or console front end,

and it's using telnet
or the telecommunication network protocol.

Telnet commonly uses TCP port 23
to provide this connection.

Just like SSH, telnet provides
this text based front end

that allows us to connect
to the remote console of another device.

But unlike SSH, all of the communication
between this telnet front end

and the telnet server
is all sent in the clear or not encrypted.

This means that anyone
who might be capturing packets between

these two devices will see everything
that you're sending over this link,

including usernames, passwords,
and everything else.

This is why we often say
that you shouldn't use telnet

on your production networks,

and instead you should always use
SSH for terminal communication.

There
are probably millions of email servers

that are located on the internet,
and the protocol that those email server

use to communicate with each other is
the Simple Mail Transfer Protocol or SMTp.

SMTp commonly uses TCP using port 25.

Not only is SMTp
used to communicate between mail servers,

but it's also used for our mail clients
to send mail to a mail server.

So if you're using a mail client on your
mobile device or your desktop computer

and you're sending an email message,
you could be using SMTp.

Although it's common to use SMTp
to send mail,

receiving mail is done using a completely
different set of protocols.

So if you were to look at your email
client, you're probably using iMap or Pop3

to be able to receive mail
and SMTp to be able to send mail.

If you need to connect to
a remote website, you would probably type

into your browser dub dub, dub dot
Professor Messer com and hit enter.

Behind the scenes,
your system needs to be able

to communicate
with the Professor Messer web server,

but it has no idea what the IP address is
for that server

to be able to resolve an IP address
from that fully qualified domain name.

Your system will use DNS
or the Domain Name System.

DNS commonly uses UDP port 53

to be able to make this connection
between you and the DNS server.

These are obviously
very critical resources

because we don't often memorize
IP addresses of servers, and very often

server IP addresses can change
without any type of notification.

It's DNS that provides that resolution
between a name

that we're typing in on the browser,
and the IP address that will be used for

the actual communication.

If you've ever

used your mobile device
on the Wi-Fi network of a coffee shop,

then you've automatically received an IP
address that you can use on that network.

This IP address was assigned
automatically using

the Dynamic Host Configuration Protocol,
or Dhcp.

The well-known ports for Dhcp are UDP

port 67 and UDP port 68.

Of course, you need a Dhcp server
to assign these IP addresses

to devices on your network,
but that functional is commonly built

into the routers and wireless
access points that we use these days.

This Dhcp server
will have a large pool of IP addresses

that can then be assigned
to devices on your network.

All of these
IP addresses are assigned in real time,

so when you start up your computer,
it queries the Dhcp server, and the Dhcp

server assigns your device
all of your IP configuration details.

Dhcp uses a leasing system
to assign these IP addresses,

so you are only using this IP address
for certain amount of time.

And after that lease expires
and you're no longer on the network,

that IP address goes back in the pool
for someone else to use.

Network administrators can also configure
Dhcp servers

to always assign
the same IP address to certain devices.

So if there are routers, firewalls,
switches, and other infrastructure devices

on your network,

your network administrator
may configure Dhcp reservations.

So those devices always receive the same
IP address every time they're booted up.

This also means that if you need to change
any of the IP configurations

on these devices,
you don't have to go to the devices

to make those changes,
you simply make them on the Dhcp server.

The next time that device requests
the Dhcp address, it will receive

the new configuration.

If you've ever used a

web browser,
then you've used Http and Https.

Http is the Hypertext Transfer Protocol,
and this is

the common protocol used by our browsers
to communicate to web servers.

There are two different protocols
depending on the type of communication

that you'll be doing.

If you're communicating in the clear
or in a non encrypted form.

You would be using the Http protocol
which uses TCP and port 80.

If your browser's communicating

over an encrypted connection,
then it's probably using Https.

The s being for secure
and that uses TCP port 443.

We mentioned earlier
that sending email messages

can use SMTp
or the Simple Mail Transfer Protocol,

but to receive email messages,
you would commonly use Pop3 or iMap.

Pop3 is the Post Office Protocol version
three, and it commonly uses TCP port 110.

Pop3 was designed to retrieve
email messages

to an email client, but it wasn't built
for multiple email clients.

And of course, these days
we tend to walk around with many different

mobile devices,
all accessing the same email inbox

to be able to synchronize across
all of these different mailboxes.

We commonly use iMap for or the Internet
Message Access Protocol version four.

iMap commonly uses TCP port 143 to be able
to download and manage that mailbox.

Many operating systems have their own
method of transferring

files and information between devices
using that operating system.

Windows
commonly uses server message block or SMB

to be able to provide this connection.

This is the protocol
commonly used by Microsoft Windows,

so if you're transferring files
between devices

or you're sending a print job
to a printer, it's probably using SMB.

You might also hear SMB referenced as CIFs
or the Common Internet File System.

SMB uses a number of different protocols
to be able to communicate,

and if you're communicating to an older
windows

machine, you're probably using net
bias over tcp IP.

Net Bios is the network basic
input output system.

This uses UDP port 137
as a name service function,

so that it can find devices
on your network by the name, and uses

TCP port 139 to set up a session
and transfer data between devices.

In most modern versions of windows
that Bios isn't used,

devices can communicate directly
between each other using TCP IP.

In those cases, it would use a direct SMB

connection using TCP port 445.

This allows us to have a direct SMB

communication
between two devices by using only TCP, IP.

If you plan on doing any work as a network
administrator,

you'll become very familiar with S&P
or the Simple Network Management Protocol.

S&P allows a network management device
to query these infrastructure devices

for performance details,
and receive those metrics in return.

This uses UDP port 161 to perform
these queries.

You can also configure
the infrastructure device to monitor

for certain metrics,
and if it exceeds any of those metrics,

it can send an alert
to the management station.

We refer to these alerts as traps,
and the traps use UDP port 162.

If you're configuring SMP on a device,
it will ask you

if you're using version one.

Version two, or version three.

Version one was obviously
the original SNMp version.

It sends structured information
across the network.

But all of this information was sent
in the clear or in a non encrypted form.

We introduced a newer version of SMP
with us AMP version two,

which allowed us to do
bulk transfers of information.

But still all of that information
was being sent in a non encrypted form.

To be able to include additional security
with us and AMP.

You need to use S&P v3.

This includes encryption
that allows us to have message integrity

authentication
and encryption of all of the SNMp data.

We use directories extensively
on our modern networks.

And one very common protocol
to use to query these directories is Ldap.

Ldap is the Lightweight
Directory Access Protocol,

and it commonly uses TCP port 389.

There are many implementations of Ldap,
but one of the most popular is Microsoft

Active Directory, which allows you
to query that Active Directory Server

using the Ldap protocol.

If you've ever worked in a support role
or on a helpdesk,

then you've probably performed some type
of remote access to someone's desktop.

One very popular protocol
to provide this remote communication

is RDP or the Remote Desktop Protocol.

This is the standard protocol
used by windows for the remote sharing,

and it commonly uses TCP port 3389.

These remote desktop services
are available in many different editions

of windows,

and if you're using windows today,
then you probably have built

into the operating system
the ability to connect to

or receive a remote desktop session.

RDP can be used to take over and control
an entire system,

or just to run a single application
from that server.

Although you'll find servers
running RDP almost exclusively on windows,

there are clients that you can run on
almost any operating system.

So if you're running Linux, Mac OS,
Android, or any other operating system,

there's probably an application
you can load that will allow you

to connect to a windows device
using the Remote Desktop Protocol.