IP Addressing
This document provides basic information needed in order to configure your router for routing IP, such as how addresses are broken down and how subnetting works.
Alternate Addressing
IP addresses are assigned to network interfaces to enable communication with other hosts in the network. It is common to see only a single IP address associated with an interface. However, at times it becomes necessary to configure more than one IP address on an interface.
Network Layers
The application layer is the highest level in the Open System Interconnection (OSI) model and is the level that is closest to you — or furthest away from you if you are at the other end of the connection. The application layer effectively moves data between your computer and the server.
The presentation layer of the Open System Interconnection (OSI) model is responsible for how that data looks or is formatted. Consider an example in which spies exchange encoded messages. The manner of passing the messages back and forth is defined by the session layer, but how the messages are encoded (or the cipher the spies used to obscure the message) is the responsibility of the presentation layer.
The session layer of the Open System Interconnection (OSI) model defines how the data is formatted between the devices on either side of the link. This is effectively the manner in which they maintain an open channel between the two devices. However, at lower levels of the OSI model, there is no permanent connection but rather a series of short bursts of data being sent back and forth.
The transport layer of the Open System Interconnection (OSI) model is closely related to the network layer, but adds functionality to it. You can think of this layer as a traffic cop or a supervisor for the mindless mob of packets that is the network layer. The transport layer takes responsibility for verifying data delivery.
The network layer of the Open System Interconnection (OSI) model routes the data from one location to another, or across several defined networks. A network is a series of devices that are connected to a single physical medium, or broadcast domain.
The second level of the Open System Interconnection (OSI) model is the data link layer. The data link layer is adjacent to the physical layer, so they are associated pretty closely together. Whereas the physical layer deals with the actual physical media (the cables and so forth that the data move over), the data link layer deals with signaling or the method used to send data across that media.
The lowest level of the Open System Interconnection (OSI) model is the physical layer which represents the physical media, such as Category 5e cables and the Ethernet frame type that is used to move the binary data across the network. Because the data is binary, it is composed of two states that represent zeros and ones: Zero is electrically off, and one is electrically on.
Transport Layers
The SSL protocol was originally developed at Netscape to enable ecommerce transaction security on the Web, which required encryption to protect customers’ personal data, as well as authentication and integrity guarantees to ensure a safe transaction. To achieve this, the SSL protocol was implemented at the application layer, directly on top of TCP (Figure 4-1), enabling protocols above it (HTTP, email, instant messaging, and many others) to operate unchanged while providing communication security when communicating across the network.
OSI/TCP Models
The OSI model and the TCP/IP models were both created independently. The TCP/IP network model represents reality in the world, whereas the OSI mode represents an ideal.
The Open System Interconnection (OSI) model has seven layers and defines what types of activities should be conducted at each layer.
DNS
The Domain Name System (DNS) is a distributed database in which you can map hostnames to IP addresses through the DNS protocol from a DNS server. Each unique IP address can have an associated hostname.
OSPF
The Open Shortest Path First (OSPF) protocol is an Interior Gateway Protocol used to distribute routing information within a single Autonomous System. This paper examines how OSPF works and how it can be used to design and build large and complicated networks.
EIGRP
Enhanced Interior Gateway Routing Protocol (EIGRP) is an interior gateway protocol suited for many different topologies and media. In a well designed network, EIGRP scales well and provides extremely quick convergence times with minimal network traffic.
STP
Spanning Tree Protocol (STP) is a Layer 2 protocol that runs on bridges and switches. The specification for STP is IEEE 802.1D. The main purpose of STP is to ensure that you do not create loops when you have redundant paths in your network. Loops are deadly to a network.
A deep understanding of the Spanning Tree Protocol (STP) is crucial to working with Ethernet switched networks. What complicates understanding is that you need to know how networks use STP before you'll understand the protocol. Sean Wilkins, co-author of CCNA Routing and Switching 200-120 Network Simulator, walks through an example to show how port states and roles, bridge IDs and BPDUs, and more are related in Cisco network devices.
HSRP
This document describes the features and functionality of Hot Standby Router Protocol (HSRP).
WAN
What is the purpose of a WAN? In this sample chapter from Connecting Networks v6 Companion Guide, explore how wide-area networks (WANs) operate, what services are available, the differences between private and public WAN technologies, and more.
Point to Point Connections
A basic understanding of point-to-point serial communications is essential to understanding protocols that are used over these types of serial links. HDLC encapsulation and configuration is discussed later in this section.
Branch Connections
A lean branch office is an architectural design option in which most business applications are delivered over the WAN and only the essential minimum infrastructure remains locally.
Broadband solutions provide teleworkers with high-speed connection options to business locations and to the Internet. In this sample chapter from Connecting Networks v6 Companion Guide, identify branch connection options for small to medium-sized businesses, basic configuration for a PPPoE connection on a client router, and more.
Network Protocols
A network protocol defines rules and conventions for communication between network devices. Network protocols include mechanisms for devices to identify and make connections with each other, as well as formatting rules that specify how data is packaged into messages sent and received. Some protocols also support message ​acknowledgment and data compression designed for reliable and/or high-performance network communication.
Network Access
As organizations are increasingly focusing on interoperability and information sharing, IoT devices, virtual servers/cloud services, routers, switches, firewalls, and bring-your-own-device (BYOD) are being flocked to their networks periodically. This poses a cumbersome task for network guardians to authenticate and authorize the endpoints in a network.
Subnetting IP Networks
Subnetting allows you to create multiple logical networks that exist within a single Class A, B, or C network. If you do not subnet, you are only able to use one network from your Class A, B, or C network, which is unrealistic.
Subnetting breaks down a given network address into smaller subnets. Coupled with other technologies like Network Address Translation (NAT) and Port Address Translation (PAT), it allows for the more efficient use of available IP address space, thereby alleviating the problem of address depletion to a great extent. Subnetting has guidelines regarding the use of the first and the last subnets, known as subnet zero and the all-ones subnet, respectively. This document discusses subnet zero and the all-ones subnet and their uses.
Dynamic Routing
This chapter explains multiple routing protocols (particularly dynamic routing protocols) and describes their relative strengths and weaknesses. It also shows how to read a routing table easily and interpret the IPv6 routing information listed within it.
Static Routing
Plugging Cisco routers together and hoping they work out of the box is not something you should hope for. A router can learn about networks in two ways: manually from configured static routers, and dynamic routing protocols.
How to configure Static Routing on wireless routers?
A static route is a pre-determined path that network information must follow to reach a specific host or network. Here are two typical scenarios, as examples of when a static route is needed, consider the following case.
Switch Configuration
This describes how to configure the IP address, subnet mask, and default gateway on the Catalyst enterprise LAN switches.
Every network engineer must have a good understanding of how trunks work in an Ethernet switching environment. Sean Wilkins, co-author of CCNA Routing and Switching 200-120 Network Simulator, shows how trunks carry traffic from multiple VLANs across switches to their configured switchports, and discusses the Cisco modes and commands that configure trunking ports.
VLANs
This chapter will cover how to configure, manage, and troubleshoot VLANs and VLAN trunks. It will also examine security considerations and strategies relating to VLANs and trunks, and best practices for VLAN design.
This chapter continues with the coverage of some of the most fundamental and important LAN topics with coverage of VLANs and VLAN trunking.
After becoming familiar with basic VLAN concepts, you need to learn how to configure your organization's networks and devices. Sean Wilkins, co-author of CCNA Routing and Switching 200-120 Network Simulator, discusses important concepts and commands you will use in setting up networks and getting devices to talk to each other.
Access Control Lists (ACLs)
One of the simplest ways of controlling the traffic in and out of a Cisco device is by using access lists (ACL). These lists are generally composed of a permit or deny action that is configured to affect those packets that are allowed to pass or be dropped. This article discusses the basic concepts of how ACLs work and shows how a basic ACL is configured.
DHCP
Cisco devices running Cisco software include Dynamic Host Configuration Protocol (DHCP) server and the relay agent software. The Cisco IOS DHCP server is a full DHCP server implementation that assigns and manages IP addresses from specified address pools within the device to DHCP clients. The DHCP server can be configured to assign additional parameters such as the IP address of the Domain Name System (DNS) server and the default device.
It is a fundamental law of networking that hosts require addressing in order to communicate. In the early days of networking, devices were often assigned static addresses, since these resources rarely moved. But static addressing of hosts doesn't scale. (Can you imagine having to manage your smartphone IP address every time you leave home?) Therefore, dynamic address configuration has become the de facto standard for the majority of networks around the world. Coffee shops, hotels, and your corporate network all utilize the Dynamic Host Configuration Protocol (DHCP) to make life a little easier for the myriad iPads, smartphones, and other computing devices that require access to your organization's network and to the Internet.
NAT
The use of Network Address Translation (NAT) has been widespread for a number of years; this is because it is able to solve a number of problems with the same relatively simple configuration. At its most basic, NAT enables the ability to translate one set of addresses to another; this enables traffic coming from a specific host to appear as though it is coming from another and do it transparently. This article looks at some of the basic concepts that are used when configuring NAT and reviews the configuration steps required to get NAT working.
Not so long ago, the Internet had a problem. There was a high demand for Internet access, but only a limited number of available Internet (IP) addresses. One solution to this problem was the creation and wide deployment of Network Address Translation (NAT), which essentially resolves multiple IP addresses into one address. This simple idea greatly extended the use of IP version 4 addresses, providing the time needed to design and implement a worthy successor—IP version 6. This article discusses the basics of NAT operation and the common NAT modes deployed in modern networks.
Windows Server 2016 Overview
This library provides info for IT pros to evaluate, plan, deploy, secure, and manage Windows Server.
Windows Server 2016 is bringing a host of new features that focus on cloud computing and virtualization.
Active Directory Domain Services
This guide contains port requirements for various Active Directory® and Active Directory Domain Services (AD DS) components. Both writable domain controllers and read-only domain controllers (RODCs) have the same port requirements.
From an operational perspective, PKI is an encryption approach where a pair of cryptographic keys -- one public and one private -- are used to encrypt and decrypt data. A user can give someone their public key, which that sender uses to encrypt data. The owner then uses their private key to decrypt the data. This authentication and encryption approach originated in the British intelligence community in the early 1970s and has been used commercially for nearly 20 years.
TCP/IP
Transmission Control Protocol (TCP) and Internet Protocol (IP) are two distinct computer network protocols. A protocol is an agreed-upon set of procedures and rules. When two computers follow the same protocols—the same set of rules—they can understand each other and exchange data. TCP and IP are so commonly used together, however, that TCP/IP has become standard terminology for referring to this suite of protocols.
IPv4
Steps to set IPv4 on Windows Server 2016.
IPv6
In this chapter from IPv6 Fundamentals: A Straightforward Approach to Understanding IPv6, 2nd Edition, author Rick Graziani examines all the different types of IPv6 addresses in the unicast, multicast, and anycast categories.
DNS
Domain Name System (DNS) is one of the industry-standard suite of protocols that comprise TCP/IP, and together the DNS Client and DNS Server provide computer name-to-IP address mapping name resolution services to computers and users.
Disaster Recovery
The objective of the vast majority of backups is to save data without errors or corruption in a way that minimizes storage space. Additional objectives also often include reducing the impact on computing resources and bandwidth usage, while making the recovery process as quick and easy as possible.
Learn which data backup type is best -- full, incremental or differential backups, or newer types of backups like synthetic and incremental-forever backups.
Windows Backup
To access backup and recovery tools, you must install the Windows Server Backup Features and subordinate items that are available in the Add Features Wizard in Server Manager.
Windows Server Essentials provides reliable ways to perform regular backups of your server and backups of your network computers. In the event of data loss, you can restore data from a successful backup on the server without restoring the entire computer. If necessary, you can perform a full system restore to your server or client computers in the network. The following table describes the different backup options available to you along with their advantages.
Group Policy
Microsoft introduced a lot of new features and capabilities in Windows Server 2016, but group policies remain largely unchanged from the previous version.
Resource Monitor
If you are running Microsoft Windows server operating system, use the System Monitor graphical tool to measure the performance of SQL Server. You can view SQL Server objects, performance counters, and the behavior of other objects, such as processors, memory, cache, threads, and processes. Each of these objects has an associated set of counters that measure device usage, queue lengths, delays, and other indicators of throughput and internal congestion.
Remote Desktop Protocol (RDP)
Remote Desktop Services (RDS) is the platform of choice for building virtualization solutions for every end customer need, including delivering individual virtualized applications, providing secure mobile and remote desktop access, and providing end users the ability to run their applications and desktops from the cloud.
E-Discovery
Electronic discovery, or eDiscovery, is the process of identifying and delivering electronic information that can be used as evidence in legal cases.
LAN Security
In this sample chapter from CCNA Cyber Ops SECFND #210-250 Official Cert Guide, explore principles of the defense-in-depth strategy, risk assessments, and more.
SNMP
Simple Network Management Protocol (SNMP) is an application-layer protocol that provides a message format for communication between SNMP managers and agents. SNMP provides a standardized framework and a common language that is used for monitoring and managing devices in a network.
TCP/IP
Learn the very basics of TCP/IP in this sample chapter by Mark Sportack. Find out how TCP/IP interacts with the internet, as well as with other communication protocols.
Route maps are similar to access lists; they both have criteria for matching the details of certain packets and an action of permitting or denying those packets. This chapter explains the basics of Route Maps. Included are sample exercises to help you practice administration and use of Route Maps.
Access Control Lists (ACLs)
In this article, we will investigate and define the different types of access control lists and examine some deployment concepts, especially the “why” we use them and the “when”. Future articles will focus on their implementation on Cisco routers, specific designs for permitting and denying services, and venture into the world of firewalls.
This document describes how IP access control lists (ACLs) can filter network traffic. It also contains brief descriptions of the IP ACL types, feature availability, and an example of use in a network.
Cryptography
With the advent of the World Wide Web and the emergence of e-commerce applications and social networks, organizations across the world generate a large amount of data daily. Data security is the utmost critical issue in ensuring safe transmission of information through the internet. Also network security issues are now becoming important as society is moving towards digital information age.
Firewalls
A firewall is a network security device that monitors incoming and outgoing network traffic and decides whether to allow or block specific traffic based on a defined set of security rules.
A firewall is a device or devices that control traffic between different areas of your network. In a more robust design you typically see two or three firewall devices, as well as many other security components to protect company resources. In a firewall design, I refer to the security solution as a firewall system, indicating that many devices are being used to protect your resources.
VPNs
Cisco DMVPN is the preferred solution for organizations requiring encrypted WAN connectivity between remote sites. Factors include the cost-driven use of the Internet to replace or provide backup for private leased lines and Frame Relay links, and regulatory pressures requiring encryption of private WAN links.
VPN tunnels are used to connect physically isolated networks that are more often than not separated by nonsecure internetworks. To protect these connections, we employ the IP Security (IPSec) protocol to make secure the transmission of data, voice, and video between sites. These secure tunnels over the Internet public network are encrypted using a number of advanced algorithms to provide confidentiality of data that is transmitted between multiple sites. This chapter explores how to configure routers to create a permanent secure site-to-site VPN tunnel.
Protection Basics
Cyber security has never been simple. And because attacks evolve every day as attackers become more inventive, it is critical to properly define cyber security and identify what constitutes good cyber security.
OS Hardening
What do we mean when we talk about “hardening systems” to repel exploits and withstand intrusions? Much of this is captured in three simple concepts: 1. Ensure a system’s security configurations are appropriately set, given the job it needs to do. 2. Ensure operating system software, firmware and applications are updated to stay ahead of exploits that attack flaws in the underlying code. 3. Ensure this process runs continually, leveraging and employing as much automation as possible
Application Security
Application security management is an essential aspect of security in the enterprise. Learn application and data security best practices in several areas, including web application security, secure coding practices, patch management & mobile application security.
BIOS
The BIOS software has a number of different roles, but its most important role is to load the operating system.
Microprocessors
The central processing unit (CPU) is the computer component that's responsible for interpreting and executing most of the commands from the computer's other hardware and software.
RAM
Random Access Memory, or RAM (pronounced as ramm), is the physical hardware inside a computer that temporarily stores data, serving as the computer's "working" memory.
Motherboards
The motherboard serves to connect all of the parts of a computer together. The CPU, memory, hard drives, and other ports and expansion cards all connect to the motherboard directly or via cables.
Power Supplies
The power supply unit is the piece of hardware that's used to convert the power provided from the outlet into usable power for the many parts inside the computer case.
Hard Drives
The hard disk drive is the main, and usually largest, data storage hardware device in a computer. The operating system, software titles, and most other files are stored in the hard disk drive.
The first thing to do after installing a hard drive is to partition it. You have to partition a hard drive, and then format it, before you can use it to store data. To partition a hard drive in Windows means to section off a part of it and make that part available to the operating system. Most of the time, the "part" of the hard drive is the entire usable space, but creating multiple partitions on a hard drive is also possible.
Peripherals
Computer hardware refers to the physical components that make up a computer system.There are many different kinds of hardware that can be installed inside, and connected to the outside, of a computer.
Operating Systems
Windows
In this post we will talk about the Windows Operating System evolution and its architecture as system software.
Apple/Mac
We'll show you how to set up your Mac and get the most use from its powerful, friendly features.
Linux
Linux is the best-known and most-used open source operating system. As an operating system, Linux is software that sits underneath all of the other software on a computer, receiving requests from those programs and relaying these requests to the computer’s hardware.
Linux Mint is one of the most popular desktop Linux distributions and used by millions of people.
The open source software platform that runs everywhere from the smartphone, the tablet and the PC to the server and the cloud.
Android
What is Android? We're not talking about robots. In this case, we're talking about smartphones. Android is a popular, Linux-based mobile phone operating system developed by Google.
This article gives you information about the history and architecture design of Android Operating System. It also covers comparisons between various other Mobile Operating Systems.
Virtualization
New software, from operating systems to applications, constantly demands more. More data, more processing power, more memory. Virtualization makes a single physical machine act like multiple—saving you the cost of more servers and workstations.
Mobile Devices
Wireless Networking
A wireless local-area network (LAN) uses radio waves to connect devices such as laptops and mobile phones to the Internet and to your business network and its applications. When you connect to a Wi-Fi hotspot at a cafe, a hotel, an airport lounge, or another public place, you're connecting to that business's wireless network.
Malware, Spyware, & Ad-Ware
Malware is a catch-all term for various malicious software, including viruses, adware, spyware, browser hijacking software, and fake security software. Once installed on your computer, these programs can seriously affect your privacy and your computer's security. For example, malware is known for relaying personal information to advertisers and other third parties without user consent. Some programs are also known for containing worms and viruses that cause a great deal of computer damage.
Viruses, worms, Trojans, and bots are all part of a class of software called malware. Malware or malicious code (malcode) is short for malicious software. It is code or software that is specifically designed to damage, disrupt, steal, or in general inflict some other “bad” or illegitimate action on data, hosts, or networks.
Troubleshooting
Do you know what to do if your screen goes blank? What if you can't seem to close an application, or can't hear any sound from your speakers? Whenever you have a problem with your computer, don't panic! There are many basic troubleshooting techniques you can use to fix issues like this. In this lesson, we'll show you some simple things to try when troubleshooting, as well as how to solve common problems you may encounter.
Whether you’re dealing with your dad’s decade-old computer or your own custom-built gaming rig, troubleshooting PC problems is a part of everyday life. Before you make that $50 support call, though, try your hand at homebrew tech support.
We have a few tips that can help you find and fix your home-built PC's problems. First, we're going to cover some troubleshooting tips, and then we'll take a look at some common issues with DIY PCs.
Assembly
To help out new PC builders and experienced enthusiasts alike, we’ve compiled this handy step-by-step guide that will take you from a pile of parts to a working computer in just a couple of hours.
Building a PC sounds daunting, but it’s actually pretty straightforward. Still, a few key details can trip up even seasoned geeks who are not being mindful. This handy-dandy guide can help you avoid the most common PC building mistakes—and their associated frustrations.
Installation
Some simple how to guides for installing Linux on your PC.
File System
Here you will find instructions and tutorials explaining how to use Linux from the command line using the BASH shell. The Linux basic fundamentals guide will take you through the necessary basics in preparation for the LPI (Linux Professional Institute) exams as well as cover many popular administration tasks.
BASH Shell
Within this tutorial we aim to provide you with an understanding of the BASH shell and its uses for scripting. This tutorial is aimed ideally at users who have a basic experience of the UNIX/Linux command line. Ideally you will need to be familiar with general navigation commands such as "cd" and familiar basic commands such as "cp", "mv", "mkdir", "find", "grep" etc.
Network Configuration
This article provides a very brief introduction to routing for Linux computers, designed for understanding simple environments.
Network Services
A list of the top 10 Services, the purpose of each service, procedure to manage this service and the corresponding configuration files for each service.