CompTIA A+ Core 1 Local Area Networking

Understanding DNS

PDU - Protocol Data Units

TCP - Transmission Control Protocol

ICMP - Internet Control Message Protocol

UPD - User Datagram Protocol

Transmission Control Protocol (TCP)- connection oriented and send multiple packets

Protocol Data Units Examples - Ethernet frames, IP packets, TCP segments

Protocol Data Units (PDU) - a single unit of information transmitted among peer entities of a computer network composed of protocol-specific control information and user data.

User Datagram Protocol (UDP) - connection less and sends multiple packets

Internet Control Message Protocol (ICMP) - connection less and sends only a single packet

We organize packets by __________ . - protocol data units (PDU)

Host files - a plain text file in an operating system used to map hostnames to IP addresses. Back then, this file was used utilized to resolve hostnames before the Domain Name System (DNS) came into existence.

DNS Root Servers - name servers that are responsible for the functionality of the Domain Name System as well as the entire Internet by translating domain names into IP Addresses.

First Level Domains Examples - .com .edu .gov .info .net .org

First Level Domains - the first-level set of domain are the top-level domains (TLDs), including the generic top-level domains (gTLDs), such as prominent domains com, edu, net, info, gov, org

Second Level Domains (SLD) - the data directly before the top-level domain (TLD). Generally the portion of the URL that identifies the website’s domain name.

Second Level Domains Example - google, amazon, Etsy

Caching Data - a process that stores multiple copies of data or files in a temporary storage location.

Cache - a software or hardware used to temporarily store information, often data, in a computer system. It is a modest form of costlier memory used to enhance the performance of frequently or often accessed data.

FQDN have a ___ character limit including dots - 256

DMARC - Domain-based Message Authentication, Reporting and Conformance

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

Domain-based Message Authentication, Reporting and Conformance (DMARC) - entered record of domains to avoid spoofing

DKIM - DomainKeys Identified Mail - enables the sender to sign their message and verify their identity.

SPF - Sender Policy Framework

Sender Policy Framework (SPF) - an email authentication method that helps to identify the mail servers that are allowed to send email for a given domain. By using ___, Internet Service Providers (ISPs) can identify emails from spoofers, scammers, and phishers as they try to send malicious email from a domain that belongs to a company or brand.

Working with DNS

Manually configure DNS -

Google’s DNS Servers - 8.8.8.8 or 8.8.4.4

nslookup -

A record - An _______ record tracks IPv4 address systems names.

AAAA Record - An ____ record tracks IPv6 address systems names.

MX records - used by mail servers

CNAME - Canonical Name record

nslookup - Use ________ to verify and DNS server is running.

ipconfig /all - Use ________ to see a system’s DNS servers.

Routers

Routers - filter and forward traffic and connect systems on a LAN

Routing Table - determines where to filter or forward IP packets

Default Gateway - Every routing table has a _______ that sends all data unless otherwise specified.

WAP - Wireless Access Point

DOCSIS - cable modem

Console port -

Serial port -

CISCO IOS (used for router interface)

DB-9 Connector - usually used for router, looks like a vga cable

Host / Rollover Cable - DB-9 cable on one end and RJ-45 connector and used for communicating with the router and made popular by CISCO

SOHO Router - Small Office/Home Office router

DHCP Range (scope) -

Change the default username and password - What is one of the most important steps when configuring a new router?

Basic Router Configuration

Static IP Address - an IP address that remains the same over time. They are often used for servers or other important equipment. Also useful when external devices or websites need to remember a device’s IP address, such as for a VPN or other remote access solutions.

Dynamic IP Address - a temporary IP address assigned to a device by an internet service provider (ISP) or network when it connects. These addresses can change over time and are often used for most devices.

Why might a dynamic IP address change? - when a user reboots their router or system, connects to their ISP, or disconnects and reconnects to a network, change based on location, how long a user has been connected to the internet

WAN - Wide Area Network

Wide Area Network (WAN) - the technology that connects your offices, data centers, cloud applications, and cloud storage together.

Static IP - _______ can be set on your WAN if required by your Internet Service Provider (ISP)

LAN - Local Area Network

pool (or scope) - DHCP servers must be configured to hand out a _______ of IP addresses.

DHCP clients - Most routers are _______.

DHCP lease - limits the amount of time a client can use an IP address

DCHP reservations - keep IP addresses for statically assigned clients

Avoid default settings for basic configurations - IP, SSID, password

Virtual LANs (VLANs)

Virtual Local Area Network (VLAN) - any broadcast domain that is partitioned and isolated in a a computer network at the data link layer (OSI layer 2). They divide a single existing physical network into multiple logical networks used to segregate different users or groups of users on the same data network.

True - Communication between two different VLANs is only possible through a router that has been connected to both VLANs.

Subnet - a way of logically dividing a network into smaller parts

True - Switches do not use IP addresses.

True - Switches only use MAC addresses.

Network Switch - connects network devices printers, computers, and wireless devices/access points, and enables users to exchange data packets.

Managed Switch - a switch device that is ideal for large networks with complex requirements such as security, traffic prioritization, and network segmentation. These types of switches often include features like Virtual Local Area Network (VLANs), Quality of Service (QoS), Access Control Lists (ACLs) and advanced monitoring capabilities.

Unmanaged Switch - a basic plug-and-play switch device with limited functionality, primarily used small networks where simple connectivity is needed. No configuration options beyond basic settings such as port speed and duplex.

Quality of Service (QoS) - a set of mechanisms used to manage network traffic and prioritize certain types of data packets, ensuring that critical applications receive the necessary bandwidth and performance, even when network congestion occurs, by controlling factors like latency, packet loss, and jitter.

Latency - the delay in the time that data takes to transfer across a network, also known as lag.

High Latency - A long delay indicates a ______.

Low Latency - A faster response time have ______.

Packet Loss - a situation where data packets sent across a network fail to reach their intended destination, meaning some data is lost during transmission and may result in reduced connection speed and disruptions such as lagging, glitches, buffering, and complete connection loss in applications like video calls, gaming and streaming services.

Network Congestion - The most common cause of packet loss is ______, where too much data is trying to travel through a network at once.

Causes of Network Packet Loss - Network congestion, wireless network issues, overloaded network devices, improper network configuration, security breach

Acceptable Packet Loss - less than 1% or 0.1%

Moderate Packet Loss - Between 2 and 5%

High Packet Loss - Above 5%

Jitter - the variation in time between when a signal is transmitted and received over a network connection. It is measured in milliseconds and is a key performance metric for networked systems.

What can cause jitter? - Network congestion, poor hardware performance, lack of packet prioritization, route changes, and improper queuing.

Jitter can cause a number of issues such as: - Choppy audio or video, difficulty uploading or downloading files, packet loss, delayed or dropped signals

Ping - One common tool for measuring jitter is _____, which calculates the average jitter in the network.

Jitter buffers or optimized network configurations - Jitter can be mitigated by ______ or ______.

Access Control Lists (ACLs) - is a list of rules that specifies which users or systems are granted or denied access to a particular object or system resource. They are installed in routers or switches, where they act as filters, managing which traffic can access the network.

Port Security -

Port Security can disable ports.

SDN - Software Defined Networking

Software Defined Networking (SDN) -

Quick Review:

True - Virtual LANs (VLANs) enable network segmentation without adding hardware.

Configure VLAN capable switches via IP address and web browser

How to manage traditional switches for VLANs? - Use firmware interface for managing VLANs and enabling port security.

Can Software Defined Networking (SDN) can lessen human error? - True.

Network Troubleshooting

No Connectivity -

IP Conflict -

Check Cables and Verify IP Address

Limited Connectivity -

Rouge DHCP Server -

Intermittent Connectivity-

Unavailable Resources -

Slow transfer/network speeds -

Quick Review

Connectivity problems are usually caused by physical or software faults

External Interference can cause network problems.

Lack of slow access to resource point to problems on the network as well.

OSI Layers

Physical Layer - Responsible for transmitting raw data bits across a network using electrical signals, light waves, or radio frequencies; manages hardware components like cables and connectors.

Data Link Layer - Provides reliable data transfer between directly connected nodes, including error detection and correction, manages the link establishment and termination.

Network Layer - Determines the best route for data packets to travel across a network, handling logical addressing and routing.

Transport Layer - Ensure reliable data delivery between applications on different hosts by managing data segmentation, flow and control, and error checking; includes protocol like TCP and UDP.

Session Layer - Establishes, manages, and terminates communication sessions between applications, including synchronization points for data transfer.

Presentation Layer - Formats data to be understood by the receiving application, including data encryption and decryption, data compression, and data conversion.

Application Layer - Provides direct interaction with user applications, including network services like email, file transfer and web browsing.

OSI model - The ______ is designed to enable different network technologies to communicate with each other by providing a common set of rules and protocols.

OSI First Layer - Physical

OSI Second Layer - Data Link

OSI Third Layer - Network

OSI Fourth Layer - Transport

OSI Fifth Layer - Session

OSI Sixth Layer - Presentation

OSI Seventh Layer - Application

TCP/IP - a practical model that addresses specific communication challenges and relies on standardized protocols

OSI - serves as a comprehensive, protocol-independent framework designed to encompass various network communication methods.

Application Layer - What is the most vulnerable layer of the OSI model?