2.6 - CompTIA A+ Core 1

DNS

Translates human-readable domain names into computer-readable IP addresses.

Root DNS

The highest level in the DNS hierarchy, denoted as '.'.

Top-Level Domains (TLDs)

The domains directly beneath the root, such as .com, .net, and .org.

Second-Level Domains (SLDs)

Domains directly beneath TLDs that include regular hostnames like 'website names'.

Subdomains

Domains that are found beneath SLDs, for example, mail.website.com.

A Record

DNS records for IPv4 that contain an FQDN with an IPv4 address.

AAAA Record

DNS records for IPv6 that contain an FQDN with an IPv6 address.

MX record

Defines the hostname for a mail server, typically a subdomain.

Text Record (TXT)

Contains human-readable text information, often used for domain verification.

DomainKeys Identified Mail (DKIM)

Provides a public key to verify a domain's outgoing mail.

Sender Policy Framework (SPF)

Lists all servers authorized to send emails for a domain, preventing spoofing.

Domain-based Message Authentication, Reporting, and Conformance (DMARC)

Provides instructions to email servers on handling emails that fail authentication.

DHCP

Dynamic Host Configuration Protocol, used for automated IP address assignment.

Lease duration

The time period a device must check in with a DHCP server to confirm it is using its assigned IP address.

Lease allocation

Lease time assigned by a DHCP server - administratively configured

Lease reallocation

Occurs when a device reboots and a DHCP server can confirm a previous lease.

T1 timer

The default time a device first attempts to renew its lease with the DHCP server, typically set to 50% of the lease time.

T2 timer

The time after which a DHCP client will attempt to contact any DHCP server to extend its lease if it has not received a response from the original server, usually set to 87.5% of the lease time.

DHCP address reservation

The process of assigning a specific IP address to a specific device based on its MAC address.

IP address scope

The range/group of IP addresses that a DHCP server can lease.

Dynamic IP assignment

The process where devices are assigned IPs automatically from a large DHCP server IP address pool.

DHCP automatic assignment

A method of IP address allocation where a device always receives the same IP address when it returns to the same network.

DNS server IP address

The IP address of the DNS server that devices will use for name resolution when configured by DHCP.

Default gateway

The IP address of the router that serves as an access point to other networks, assigned by DHCP.

Virtual Local Area Network (VLAN)

A group of devices in the same broadcast domain that are separated logically and cannot communicate with each other.

Local area network (LAN)

Refers to a group of devices in the same broadcast domain, connected by the same router/switch.

Advantages of VLANs over separate switches

More efficient to buy a single device and configure two separate broadcast domains virtually, halving device costs, power costs, and configuration time.

VPN (Virtual Private Network)

A network architecture that encrypts data traveling via a public network to maintain confidentiality.

Concentrator

An encryption/decryption access device, often integrated into a firewall, used in VPNs.

Client-to-site VPNs

A setup where the client activates the VPN to create an encrypted tunnel to the VPN concentrator.

Purpose of VLAN segmentation

To enhance security by limiting communication from non-admin workstations to important servers.

Disadvantages of using two separate switches for LANs

Involves higher costs for power and purchase, as well as separate configuration for multiple devices.