2.1 - Common Network Ports Flashcards
In addition to the server and the client, what other devices might need to know well known port numbers?
Firewalls. They often make the decision on what traffic to allow and disallow based on the port number.
What port(s) are used by FTP?
TCP/20 for data transfer, and TCP/21 for controlling the data transfer.
What is FTP used for?
Used for transferring data between devices, usually requiring some sort of authentication to the remote device. It can also have additional functionality to list, add, and delete files.
What is SSH used for?
Connecting to a remote device through a terminal or command-line front end. The data sent over the network is encrypted, hence “secure”.
What port(s) does SSH use?
TCP/22.
What is Telnet?
Telecommunication network. Similar to SSH, provides a text-based way to access a remote device.
Why might one prefer SSH over Telnet?
Unlike Telnet, SSH sends its data encrypted. Telnet sends “in the clear”.
What port(s) does Telnet use?
TCP/23.
What is SMTP and what is it used for?
Simple Mail Transfer Protocol. Used for server to server email transfer, and for mail clients to send emails to servers. Note: NOT used to receive email.
What port(s) does SMTP use?
TCP/25.
What does DNS do?
It converts the fully qualified domain name (i.e., professormesser.com) to an IP address (162.159.246.164).
What port(s) does DNS use?
UDP/53.
What is DHCP and what is used for? Whence come the servers?
Dynamic Host Configuration Protocol. Used to automatically assign a device an IP address when it is connected to the network. DHCP servers are usually built into routers and access points that we use these days.
What port(s) does DHCP use?
UDP/67 and UDP/68.
What does it mean for IP addresses on a DHCP server to be “dynamic”, “pooled”, and “leased”?
“Dynamic” refers to the fact that they are assigned in real time. “Pooled” means that there is a pool on the server from which IP addresses are assigned. “Leased” means that each device is given a lease that it must renew at set intervals. If it does not, those IP addresses go back to the pool.
What is DHCP reservation?
A specific IP address is reserved for a specific device on the server.
What are HTTP and HTTPS, and what are they used for?
Hypertext Transfer Protocol and Hypertext Transfer Protocol Secure. Used mostly for communication in the browser.
What is the main difference between HTTP and HTTPS?
Communication over HTTPS is “secure”, which is to say encrypted.
What port(s) does HTTP use?
TCP/80.
What port(s) does HTTPS use?
TCP/443.
What does POP3 stand for?
Post office protocol 3.
What port(s) does POP3 use?
TCP/110.
What does IMAP4 stand for?
Internet Message Access Protocol v4
What is the advantage of IMAP4 vs POP3?
IMAP4 is better suited for when multiple clients need to access the same inbox.
What port(s) does IMAP4 use?
TCP/143.
What is SMB, what is it used for, and how else is it known?
Server Message Block - a protocol used by older Microsoft Windows machines for file transfer and printer sharing. AKA CIFS - Common Internet File System.
What is NetBIOS over TCP/IP?
Network Basic Input/Output System. Allows for applications on different machines to communicate over a LAN (Local Area Network).
What is nbname and what does it do?
NetBIOS name services, allows you to find devices by their name.
What port does nbname use?
UDP/137
What is nbsession and what does it do?
NetBIOS session service, allows you to setup a session and transfer data between devices
What port does nbsession use?
TCP/139
What is the alternative to NetBIOS in modern Windows machines?
Creating a direct SMB communication over TCP.
What does SNMP stand for, and what is it used for?
Simple Network Management Protocol - allows for network management devices to gather statistics from network devices.
What port does SNMP use for queries?
UDP/161
What port does SNMP use for traps?
UDP/162
What is a trap in the context on SNMP?
An alert that is sent by the network device.
What is LDAP and what does it do?
Lightweight Directory Access Protocol, used to query directories.
What port(s) does LDAP use?
TCP/389
What is one of the most common implementations of LDAP?
Microsoft Active Directory.
What does RDP stand for, and what is it used for?
Remote Desktop Protocol. Used to share a desktop from a remote location.
What port does RDP use?
TCP/3389.
On what server and client devices are RDP used?
RDP servers are almost exclusively on Windows computers, but clients exist for all OS’s.
What port(s) does SMB use?
TCP/445
