220-1201 Networking Study Guide for the CompTIA A+ Core Series Exam

Networked Host Services

A networked host service is a service that provides resources and functionalities to network-connected devices, or clients, through a centralized network device, or server. You need to have a working understanding of the properties and purpose of network-delivered services in a client-server environment and know how to summarize them.

Server Roles

You are expected to have a working understanding of the following network services. A server is not necessarily a stand-alone piece of hardware. A server is usually a process running in memory on a networked system that responds to requests from a remote client system.

Domain Name System (DNS)

DNS servers resolve hostnames to IP addresses. Two public DNS servers are needed for an enterprise to host a website, with one DNS server acting as a redundancy. Records of hostname IP address sets are held in a zone file. If the DNS address is not located in the zone file, it requests the information from a higher-level DNS server called the root server.

Dynamic Host Configuration Protocol (DHCP)

A DHCP server provides IP configuration information, such as an IP address, subnet mask, default gateway, and DNS server address, automatically to clients. The scope of a DHCP server is the information that is permitted to be shared with a client, including the IP address, subnet mask, default gateway, domain name, and any other information the DHCP server may hold.

Fileshare

A fileshare or file server is a central repository for the storage, management, and access of network files. A network can also use network-attached storage (NAS) for a file server.

Print Servers

A print server is a server that manages print requests and connects printers to a network. Print servers can be either hardware, software, or cloud-based. They increase security by filtering access, enforcing policies, and prioritizing print jobs.

Mail Servers

A mail server is responsible for sending, receiving, and managing emails. A mail server must be running a specialized server package, such as Microsoft Exchange, Sendmail, Postfix, or Exim, to be considered a mail server.

Syslog

The syslog server in a client-server model is responsible for collecting information obtained through system monitoring, such as login events or errors. Messages compiled in a syslog server include the facility code, the severity level, and a textual description of the logged events. Syslog servers are composed of three primary components: the listener, the database, and the management and filtering software.

Web Servers

A web server is a device that stores and manages files related to websites. A web server receives requests for website access, locates the appropriate files, and responds to the request through the HTTP protocol.

Authentication, Authorization, and Accounting (AAA)

A web server listens for incoming requests. The requests are executed by the web server and provide the requested content, including text, images, videos, and the running of scripts. Common web server platforms include Microsoft’s Internet Information Services (IIS) and the open-source Apache.

Database Servers

A database server is a device that allows for the use of and interaction with a central repository for a database. A database is a collection of highly structured information that is used for data retrieval by applications, websites, analytics, and numerous other computing programs.

Network Time Protocol (NTP)

An NTP server is a device that is used for time synchronization across a network. The NTP server uses an authoritative time source, such as an atomic clock, as a time reference, facilitating a secure and accurate exchange of data.

Internet Appliances

An internet appliance is a device that aids in internet access while ensuring that access is safe.

Spam Gateways

A spam gateway, also known as an antispam gateway, is an internet appliance whose purpose is to block malicious emails from accessing the network.

Unified Threat Management (UTM)

UTM acts to centralize security management on a network. UTM typically provides packeting filtering and inspection, an intrusion prevention system (IPS), gateway anti-malware, spam blocking, malicious website blocking, and application control.

Load Balancers

A load balancer is responsible for evenly distributing requests over servers to balance the system. Common load balancing configurations include identical, cross-region, and content-based.

Proxy Servers

A proxy server makes requests for resources on behalf of a client. The proxy server acts as an intermediary between the client and the target server.

Legacy/Embedded Systems

Legacy systems are older systems that, for one reason or another, have not been updated. It is usually due to essential applications that will not run on the updated platform. Embedded systems are devices other than computers that have computer technology running within. Like legacy systems, these may not be able to stay updated.

Supervisory Control and Data Acquisition (SCADA)

A SCADA system is a high-level management system used to control manufacturing machines and processes, manage large-scale infrastructure settings, and run building components. While newer or updated SCADA systems utilize updated technologies including IoT, cloud computing, and increased cybersecurity technologies, older SCADA systems are considered to be an example of critical legacy systems. A critical legacy system is one that is still extremely integral for daily operations despite the outdated technology or security risk it may pose.

Internet of Things (IoT) Devices

An IoT device connects to the network through a central controller or coordinating device. Common examples of IoT devices include smart devices such as thermostats and home automation and security devices.

Network Configuration

You must be able to explain, compare, and contrast common network configuration concepts for the CompTIA A+ exam.

Domain Name System (DNS)

The DNS has only one function: to resolve hostnames to IP addresses. 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.

Addresses are contained on the DNS server in zone files. The zone file maintains records of hostname-to-IP address mappings and contains information such as the name of the server or computer, the IP address, the record type, the computer address, and comments. DNS zones are arranged in a hierarchical pattern starting at the root zone and progressing downward, allowing for more granular control at each subsequent level. The fully qualified domain name (FQDN) specifies the unique path to a specific network resource in the DNS system and is composed from the bottom of the hierarchy up to the final implied “.” at the root zone.

Retrieved from: https://commons.wikimedia.org/wiki/File:DNS_schema.svg

DNS Record Types

There are various DNS record types that serve different purposes. These are the most important:

• A is a common DNS record type that signifies that the host record is an IPv4 address.

• AAAA (pronounced “quad A”) is a common DNS record type that signifies the host record is an IPv6 address.

• A canonical name (CNAME) record contains aliases and subdomains related to the primary record.

• A mail exchanger (MX) record is a common DNS record type that signifies that the host record is the name or address of an email server.

• A text (TXT) record is a common DNS record type that signifies that the host record is a text record for human-readable or machine-readable data.

Spam Management

Spam management is the process of determining if data is spam or valid. There are various tools that can perform this role:

• DomainKeys Identified Mail (DKIM)—DKIM is a type of spam management that authenticates using encryption through a public-private key pair.

• Sender Policy Framework (SPF)—SPF is a type of spam management that authenticates an email server based on its IP address.

• Domain-Based Message Authentication, Reporting, and Conformance (DMARC)—DMARC is a type of spam management that combines DKIM and SPF in one framework and offers more control over what the user can do with spam email.

Dynamic Host Configuration Protocol (DHCP)

The DHCP automatically assigns all of the settings needed to access resources on your local area network (LAN) or the internet. It can provide IP address, subnet, gateway, and DNS information. If you want to ensure that a device gets a specific IP address, you can configure a DHCP reservation in the DHCP server.

Leases

A lease is a temporary IP configuration assigned by the DHCP server to a client. A lease typically includes an IP address, subnet mask, default gateway, and DNS server address.

Reservations

A reservation is the reserving of an IP address for a specific client based on the client’s media access control (MAC) address and is primarily used for devices that require a static IP address.

Scope

The scope is information provided outside the IP address and the subnet mask issued by the DHCP server, such as the default gateway, DNS server address, or domain name.

Exclusions

An exclusion is a defined address or set of addresses within the IP pool that are unavailable for DHCP assignment. Exclusions are commonly used to ensure available IP addresses for static address assignment.

Virtual Local Area Network (VLAN)

A VLAN is a logical subnet, typically configured on a switch, that acts as a separate subnet. Without VLANs, every device connected to a switch would be on the same subnet. By configuring VLANs on the switch, you can have devices on that one switch in different subnets or VLANs.

Virtual Private Network (VPN)

A VPN is an encrypted connection between two networks or between a host and a network. When a host connects to a network over a VPN, it is assigned a separate IP address that is in the network’s address range.