220-1101 Networking Study Guide for the CompTIA A+ Core Series Exam
Understanding all types of networks and their corresponding connections is vital if you are in an IT support position. You will need to know everything about TCP/IP, Wi-Fi, and SOHO connections. About 20% of the CompTIA A+ 1101 test concerns various aspects of networking. Around 25% of the questions concerning networking will begin with a scenario.
Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) Ports
For the CompTIA A+ exam, you must be able to compare and contrast TCP and UDP ports and protocols and their respective purposes. Memorizing port numbers is highly recommended for this section.
Ports and Protocols
For this exam, you should know the following TCP/UDP port numbers, the protocols that run over those ports, and the primary use for each. A port is the unique identifier number for transmission control and direction. A protocol is a set of rules that govern communications.
20/21—File Transfer Protocol (FTP)
File Transfer Protocol (FTP) is used to manipulate files. FTP can copy files, list and manipulate directories, and view file contents. FTP runs on ports 20 and 21. Port 21 is mainly used for file management and port 20 is used for data transfer. FTP is not secure and transmits in plain text.
22—Secure Shell (SSH)
Secure Shell (SSH) is a connection-oriented protocol used to set up secure Telnet connections for remote logins. SSH is secure and runs on port 22.
Telnet is a terminal emulation program that allows for remote access to text on another computer. Telnet is not secure and transmits plaintext. Telnet uses port 23.
25—Simple Mail Transfer Protocol (SMTP)
Simple Mail Transfer Protocol (SMTP) is used to send email only and is a push protocol. SMTP uses port 25.
53—Domain Name System (DNS)
The Domain Name System (DNS) is used to resolve hostnames to IP addresses and uses port 53.
67/68—Dynamic Host Configuration Protocol (DHCP)
Dynamic Host Configuration Protocol (DHCP) assigns IP addresses dynamically to network clients. DHCP uses port 67 for the server and port 68 for the client.
80—Hypertext Transfer Protocol (HTTP)
Hypertext Transfer Protocol (HTTP) manages communications between a web server and a client to view internet content. HTTP is not secure and transmits in plain text. HTTP uses port 80.
110—Post Office Protocol 3 (POP3)
Post Office Protocol 3 (POP3) is used for downloading email. POP3 uses port 110.
137/139—Network Basic Input/Output System (NetBIOS)/NetBIOS over TCP/IP (NetBT)
Network Basic Input/Output System (NetBIOS) is an API for communication between computers over a network. NetBIOS works over OSI layer 4 and needs to work with a layer 5 protocol, namely TCP/IP, to function properly. NetBIOS over TCP/IP is called NetBT. NetBIOS runs on ports 137/139.
143—Internet Message Access Protocol (IMAP)
Internet Message Access Protocol (IMAP) is currently in its fourth version, or IMAP4, and is used for downloading email. IMAP4 is secure and runs over port 143.
161/162—Simple Network Management Protocol (SNMP)
Simple Network Management Protocol (SNMP) is used for network management. SNMP uses port 161 for sending and receiving requests and port 162 for receiving transmissions from managed devices.
389—Lightweight Directory Access Protocol (LDAP)
Lightweight Directory Access Protocol (LDAP) is used for accessing information stored in an information directory. LDAP uses port 389.
443—Hypertext Transfer Protocol Secure (HTTPS)
Hypertext Transfer Protocol Secure (HTTPS) is the secure version of HTTP. HTTPS uses port 443.
445—Server Message Block (SMB)/Common Internet File System (CIFS)
Server Message Block (SMB) is primarily a Microsoft protocol used for shared file access. Common Internet File System (CIFS) is an enhanced version of SMB. SMB/CIFS use port 445.
3389—Remote Desktop Protocol (RDP)
Remote Desktop Protocol (RDP) allows for remote connection to computers. RDP uses port 3389.
TCP vs. UDP
Transmission Control Protocol (TCP) is a connection-oriented protocol used to send and receive data over a network. Before data is sent, a connection is established with the receiving host. It is considered a reliable protocol because the receiving host acknowledges that it received the data. TCP is used in cases where receiving the proper data is more important than speed. User Datagram Protocol (UDP) is a connectionless protocol. Data is sent without any assurance that the receiving host is actually receiving the data. For that reason, it is considered an unreliable protocol. The advantage of UDP over TCP is that it is faster.
Connectionless protocols allow for data to flow without guaranteeing an established connection. This allows for faster data flow but does not guarantee reliable data flow. UDP is connectionless.
DHCP—Dynamic Host Configuration Protocol (DHCP) is used to dynamically assign IP configuration information to clients through a lease and uses UDP as its transport protocol. DHCP runs on port 67/68.
TFTP—Trivial File Transfer Protocol (TFTP) is a faster version of FTP that uses UDP rather than TCP as its transport protocol. TFTP uses port 69.
Connection-oriented communication establishes a set connection before data flow begins between two devices. TCP is connection-oriented.
HTTPS—Hypertext Transfer Protocol Secure (HTTPS) is a connection-oriented protocol that uses TCP as its transport protocol. HTTPS uses port 443.
SSH—Secure Shell (SSH) is a connection-oriented protocol that uses TCP as its transport protocol. SSH uses port 22.
Common Networking Hardware
Networking hardware includes the physical components used to achieve network connectivity. You must be able to compare and contrast common networking hardware.
A router is a device that connects multiple network devices and determines the best path for reaching a specified device using routing tables. Routers are OSI Layer 3 devices and make decisions based on logical addresses. Key functions of a router include connecting multiple network devices to one another, breaking up broadcast domains, and connecting one LAN to another LAN on a WAN.
A switch is a device that works at OSI Layer 2, examines the header of incoming packets for the MAC address, and forwards the packet to the correct location. Switches can be managed or unmanaged.
A managed switch is one that allows for port configuration, traffic management, and traffic monitoring. Managed switches offer quality of service (QoS), redundancy, port mirroring, and VLANs.
An unmanaged switch does not allow for configuration and passes on all data for a MAC address to its ports.
An access point is technically any device to which a host can connect in order to access a network. Wired access points include hubs and switches. However, the term usually refers to a wireless access point (WAP) that allows Wi-Fi devices to connect to a network.
A patch panel is a dumb device that is essentially a large rack-mounted HUB whose sole purpose is to connect cables together. A dumb device is a device that broadcasts all data coming in through the input port out over all output ports. A dumb device, like a patch panel, makes no logical decisions and simply serves as a connection and relay point.
A firewall is a security appliance, either hardware or software, that filters network traffic based on a preconfigured set of rules.
Power over Ethernet (PoE)
Power over Ethernet (PoE) is a technology that delivers power to devices over data lines, such as an ethernet cable, rather than having a separate power cord.
An injector is a midspan device that sits between the switch and the access point and supplies power via an ethernet connection.
A switch sits in front of the midspan injector device and provides power to the ethernet cable.
PoE standards are the IEEE 802.3 standards that define PoE specifications.
- PoE- 802.3af-15.4 W—WAPs, static surveillance cameras, VoIP phones
- PoE+- 802.3at-30W—alarm systems, PTZ cameras, video IP phones
- PoE++- 802.3bt (Type 3)-60 W—multi-radio WAPs, video conferencing equipment
- PoE++- 802.3bt (Type 4)-100 W—laptops, flat-screen monitors
A HUB is a dumb Layer 1 device that sends all incoming data to all connected devices as a broadcast. Hubs are also known as multiport repeaters.
A cable modem is a device that connects to a cable line to provide connectivity. A cable modem is technically no longer a modem, however, since it does not modulate and demodulate analog signals.
Digital Subscriber Line (DSL)
A digital subscriber line (DSL) modem provides connectivity via a telephone line.
Optical Network Terminal (ONT)
An optical network terminal (ONT) modem is one that provides connectivity via a fiber-optic line.
Network Interface Card (NIC)
A network interface card (NIC), also known as a network adapter card, is used to provide the physical interface between a computer and the cabling used for connectivity.
Software-Defined Networking (SDN)
Software-defined networking (SDN) sets up a network virtually via the cloud. The SDN replaces the functionality of the router in a network.
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