Page 2 901 Networking Study Guide for the CompTIA® A+ exam

TCP and UDP Ports, Protocols, and Purposes

For this exam, you should know the following TCP/UDP port numbers, as well as their primary use.


You should know the names of the following common port numbers and understand their usage.

21 – FTP: File Transfer Protocol; used to transfer files to a server

22 – SSH: Secure Shell; used to access remote devices with added encryption

23 – TELNET: used to access remote devices with no encryption

25 – SMTP: Simple Mail Transfer Protocol; used for sending e-mail

53 – DNS: Domain Name System; translates domain names to IP addresses

80 – HTTP: Hypertext Transfer Protocol; standard for communication on the web

110 – POP3: Post Office Protocol 3; used for receiving e-mail

143 – IMAP: Internet Message Access Protocol; used for receiving e-mail

443 – HTTPS: Secure Hypertext Transfer Protocol; secured communication on the web

3389 – RDP: Remote Desktop Protocol; used to connect to remote computers

137-139 – NetBIOS/NetBT: Network Basic Input Output System; used for LAN communication

445 – SMB/CIFS: Server Message Block/Common Internet File System; used for shared access on a network

427 – SLP: Service Location Protocol; used for local service discovery

548 – AFP: Apple Filing Protocol; used for Apple file services


Be sure to know these protocols and the services they offer.

DHCP: Dynamic Host Configuration Protocol

DNS: Domain Name System

LDAP: Lightweight Directory Access Protocol

SNMP: Simple Network Management Protocol

SMB: Server Message Block

CIFS: Common Internet File System

SSH: Secure Shell

AFP: Apple Filing Protocol


TCP: Transmission Control Protocol is a connection-oriented protocol that requires an established connection before sending data to a receiver. This is done by what is known as a TCP handshake.

UDP: User Datagram Protocol (UDP) is a connectionless protocol. This requires no formal established connection before sending data. It is typically used in live streaming applications, such as live TV.

WiFi Networking and Encryption

For your exam, you should also demonstrate the ability to compare various types of wireless technologies and their associated encryption mechanisms.


802.11a: 5Ghz frequency, maximum speed of 54mbps and maximum distance of 150 feet, not much in use today

802.11: 2.4GHz frequency, maximum speed of 11mbps and maximum distance of 300 feet

802.11g: 2.4GHz frequency, maximum speed of 54mbps and maximum distance of 300 feet

802.11n: 2.4 and 5GHz frequencies, maximum speed of 600mbps and distance can reach over 300 feet

802.11ac: 5GHz frequency, maximum speed of 7gbps and distance can reach over 300 feet, newest technology

Encryption Types

WEP: Wired Equivalent Privacy; uses RC4 cipher; weakest of all encryption types

WPA: WiFi Protected Access; uses RC4 cipher, but includes TKIP; quick upgrade for WEP

WPA2: WiFi Protected Access 2; more permanent upgrade to WEP and uses AES technology

TKIP: Temporal Integrity Key Protocol; encryption mechanism that requires a new key with every packet of traffic

AES: Advanced Encryption Standard; a block cipher using a 128-bit block size; also uses up to 256-bit key.

SOHO Routers

In this exam, you will be tested on your ability to configure a SOHO network and achieve optimal operability using the proper settings.


Most modern routers will automatically adjust their channels and frequencies, so they are not interfering with other wireless devices in the area. You can also set this manually.

Port Forwarding/Port Triggering

Port Forwarding allows you to directly communicate with a device on the Internet by using a static mapping inside of the router.

Port Triggering is similar to forwarding, but the forwarding will only be active when defined conditions are met, such as when you are playing a certain game.

DHCP (on/off)

DHCP can be used to automatically hand out IP addresses on your network. If this setting is off, you will have to manually enter in the IP address information on each device. Turning this off is not more secure and can create a false sense of security.


This allows services or devices that are inside your network to be placed on a special, protected network that is reachable from the Internet and prevents Internet traffic from accessing the secured portion of your network.


NAT is completed on the router to allow devices inside the network with private IP addressing to access external resources. This is typically done automatically without intervention.

Basic QoS

This is a service seen on higher end devices and it allows you to prioritize certain traffic on your network. For example, you could configure voice traffic to take precedence over Xbox traffic.


Updating your router’s firmware can add capabilities to your device. You should always have a backup copy in case you need to revert back to the previous version.


Universal plug and play allows certain devices inside your network to automatically configure your router, allowing them to connect outside to the Internet. This can create security concerns.