Page 1 901 Networking Study Guide for the CompTIA® A+ exam
How to Prepare for the Networking Questions on the CompTIA A+ 901 Test
On the CompTIA A+ 901 test, networking is the topic of about 21% of the questions. You not only need to know terminology but also be able to problem-solve in this area, given a certain situation or scenario. The following objective lists may not contain absolutely everything that might come up on the test, but they’ll give you a good idea of the areas in which you need to be well-versed.
Types of Cables and Connectors
For this exam, you need to know and identify various types of primary cables and their corresponding connectors, including fiber, twisted pair, and coaxial.
SC is a subscriber connector and uses a square connector.
ST is a straight tip connector and uses a bayonet connection, similar to BNC.
LC is a lucent connector. It has a similar square size type as SC, but is smaller in size.
Memory trick: If you can memorize “ST is like BNC,” then just think of SC as Square, and LC as Little Square.
RJ-11 is a two-pair (4 wire) copper connector, typically used with analog phone lines.
RJ-45 is a four-pair (8 wire) copper connector, typically used with ethernet lines.
T568A is a wiring standard for twisted pair cabling. Pins 1, 2, 3, and 6 are wired differently from T568B.
T568B is also wiring standard for twisted pair cabling, and it is the most common type.
BNC is a bayonet-type connection that twists and locks into place.
F-Connector is commonly used with cable modems and on RG-6 cabling.
Characteristics of Connectors and Cabling
For this exam, you should be able to compare and contrast the various types of cabling and connectors in the exam blueprint, including fiber, coaxial, and twisted pair.
Single-Mode Fiber (SMF) is used for long distance runs (greater than 2 kilometers) and typically uses a laser as a light source.
Multi-Mode FIber (MMF) is used for shorter distance runs (less than 2 kilometers) and typically uses LED as a light source.
Shielded Twisted Pair (STP) is a twisted pair cabling that provides an extra layer of protection inside the cable to help with shielding from interference. Each end of the shielding should be grounded.
Unshielded Twisted Pair (UTP) is a twisted pair cabling that does not have any extra protection inside the cable itself to help shield it from interference.
CAT3 is an early use ethernet cable that ran at speeds of 10mbps up to 100 meters. This technology has been deprecated.
CAT5 is an upgrade from CAT3 ethernet that allowed speeds of 100mbps and 1gbps up to 100 meters. This technology is also deprecated.
CAT5e for enhanced was an upgrade from CAT5 and allows the same speeds as its predecessor. This enhanced technology allows you to get the 1gbps speeds at cable runs up to 100 meters, something regular CAT5 had issues with, sporadically.
CAT6 was created to account for new speeds up to 10gbps. This was limited drastically from the distances of other standards, topping out at 55 meters.
CAT6e was an enhanced version, commonly known as CAT6A, which allowed the full 10gbps at distances of 100 meters.
CAT7 is a newer version of CAT6, which allows shielding of the cabling at the same speeds and distance of 10gbps and 100 meters, respectively.
Plenum cable is used to run in shared plenum space, typically above a drop ceiling. This special type of cable helps to reduce the chemicals that may burn off the cabling during a fire.
Polyvinyl Chloride (PVC) is used in standard network cabling as a jacket for the cables.
Splitters allow you to use the wires in the cabling for more than one device. This is typically not recommended and can adversely affect the quality.
RG-6 is used for longer cable runs, typically for the service providing company for carrying Internet or digital applications.
RG-59 is used by service providers for shorter cable runs, typically found inside of buildings. RG-59 is not intended to carry ethernet traffic since it has an impedance of 75 ohms. Very early ethernet implementations used RG-8 and/or RG-58, which had an impedance of 50 ohms.
Splitters allow you to split the signal for use with more than one device. This is typically not recommended and can adversely affect the quality and speed.
TCP/IP Properties and Characteristics
For this exam, you should be familiar with the properties and characteristics of several features of the TCP/IP protocol suite, including IPv4 and IPv6, DHCP and DNS.
IPv4 vs. IPv6
IPv4: Internet Protocol Version 4 is a 32-bit address used for IP communication. Its address is separated into 4 octets, with 1 to 3 numbers in each octet.
IPv6: Internet Protocol Version 6 is a 128-bit address used for IP communication. This was the result of an overhaul to IPv4, as the depletion of IP addresses began to become a concern. IPv6 solves this problem, creating a total of 340 undecillion unique addresses, or 2^128.
Public vs. Private vs. APIPA/Link Local
Public: A public address is one that is routable and reachable on the Internet. This is typically used in WAN applications to communicate across a service provider’s backbone network.
Private: A private address is one that is not routable via the Internet, and it is used only for local communication within a LAN. An ISP will block private IP addresses to/from the Internet. These are defined in RFC 1918 for further research.
APIPA: Automatic Private IP Addressing is a Microsoft-developed protocol, which assigns you an IP address within a reserved, private class when you have failed to receive an IP address from a Dynamic Host Configuration Protocol (DHCP) server. This address will always begin with 169.254.
Static vs. Dynamic
Static: A static address is one that is put in manually by a user or administrator. It is often used in smaller or niche environments that do not utilize dynamic addressing.
Dynamic: A dynamic address is one that is automatically assigned, typically by a router or DHCP server. This is typically used in larger environments with lots of nodes.
Client-Side DNS Settings
Domain Name System (DNS) settings are usually given out via DHCP along with IP address information, but this can be done manually as well. This allows the user (client) to resolve domain names to IP addresses in order to perform searches or lookups. These are usually given out in a primary and secondary fashion for redundancy purposes.
Dynamic Host Configuration Protocol (DHCP) allows your device to be automatically configured with all of the settings needed to access resources on your LAN or the Internet. It can provide DNS, IP address, Subnet, and Gateway information.
Subnet Mask vs. CIDR
Subnet Mask: A subnet mask identifies the network and broadcast address to which a user or host belongs.
CIDR: Classless Inter-Domain Routing (CIDR) defines address masking on non-classful boundaries. Typically, an IP address would have to fall into its assigned Class A, B, or C mask; This is known as classful addressing. Classless addressing allows addresses to be assigned outside of these scopes. CIDR notation typically involves the use of a slash (/) to represent the subnet mask.
A gateway is typically the internal IP address assigned to the inside of your firewall or router, which allows you to leave the local network (LAN) and access resources on the public Internet (WAN). The gateway device usually performs some sort of IP address translation from private to public address and vice versa. This is known as NAT.