Networking Basics & LAN Flashcards
Host
Local Host
Remote Host
Host: Any computing device connected to a network.
Local Host: Your own computer/device.
Remote Host: Another computing device on the network or reachable beyond the network.
Web Server
+
2 Web Server Programs
Stores files that make up a website.
Uses server programs to store/share the data.
Programs:
Apache HTTP
IIS (Microsoft Internet Information Services)
File Server
A networked host that enables you to access a bunch of files/folders.
Mail Server
A networked host that allows access to email.
Resource
Anything one computer might share with another.
Legacy System
An old method, technology, computer system, or application that is outdated but still in use.
Embedded System
A computer system that has a dedicated function with a larger mechanical or electrical system.
NIC
Network Interface Controller (C used to be Card):
Define/label a machine on a network.
Breaks files into smaller data units to send across the network. Reassembles units it receives to whole files.
Frames
(Packets are included in frames)
+ 4 Parts
Discrete chunks of data that NICs move from one devices to another.
4 Parts:
MAC address of network card receiving data
MAC address of network card sending data
Data itself
Data check with algorithm (CRC = Cyclic Redundancy Check)
MAC Address
Media Access Control:
48-bit binary number (281 Trillion + in existence)
Total of 12 hexadecimal characters
Some NICs allow MAC addresses to be changed (rare)
Hexadecimal
One hex character represents a string of 1s and 0s.
C = 1100 2 = 0010 9= 1001
1 - 9 & A - F
Ethernet (General)
A series of standards that defines everything necessary to get data from one computer to another.
Mid 1970s by Intel, Xerox, Digital Equipment Corp
Hundreds of distinct improvements: “Flavors”
Ethernet Speed Categories (Main 3)
10BaseT = 10Mbps 100BaseT = 100Mbps 1000BaseT = 1000Mbps or 1Gbps (Gigabit)
Star Bus Topology
A central box (switch) that each individual host connects to.
“Star” comes from the idea of the switch being in the center and the wires to computers spreading out like a star.
Switch
Provides a common point of connection for network devices.
Wide variety of ports; each port is treated as a separate network.
“Smart Repeater”: Memorize MAC of all connected devices & only sends repeated signals to the correct host. (Unlike Hubs)
Hub
A basic “repeater”:
Anything sent in one port goes to all other ports.
Replaced by switches.
Segment
A connection between a computer & switch.
Ethernet segments = 100m max
Splitters wouldn’t work with segments (negative effect on signal quality).
Switch wouldn’t recognize which host is sending/receiving.
UTP
Unshielded Twisted Pair:
Specified cabling for 10/100/1000BaseT
AWG 22-26 gauge wire twisted together into color-coded pairs.
Come in categories that define transfer speed.
UTP Categories
Established by ANSI/TIA
Cat 1: Telephone line Cat 3: 10Mbps Cat 5: 100Mbps Cat 5e: Enhanced to handle 1000Mbps Cat 6: Gigabit @ 100m (10Gbps = 55m) Cat 6a: 10Gbps @ 100m Cat 6e: nonstandard; means Cat 6 or Cat 6a Cat 7: 10Gbps @ 100m + shielding to reduce noise (^^^ NOT an ANSI/TIA standard ^^^)
Solid Core UTP
Uses a single solid wire.
Better conductor.
Stiff, can break if handled too often/roughly.
Horizontal cabling should always be solid core.
Stranded Core UTP
Each wire is a bundle of tiny wire strands.
More durable for handling.
Not as good of a conductor as solid core.
STP
Shielded Twisted Pair:
Twisted pairs of wires surrounded by a shielding to protect from EMI.
Useful in locations with excessive electronic noise.
Ethernet Types w/UTP Categories
10BaseT = Cat 3 at least; typically Cat 5 100BaseT = At least Cat 5 1000BaseT = Cat 5e or higher
RJ-45
Registered Jack 45
Standard for UTP connectors (4 pairs)
Wider than RJ-11 (telephone jack)
T568A vs. T568B
RJ-45 standards (color coding is different)
Hint: orange & green switch! everything else stays
T568A:
G-W, G, O-W, BL, BL-W, O, BR-W, BR
T568B:
O-W, O, G-W, BL, BL-W, G, BR-W, BR
RJ-11
Standard for telephone lines & telephone-based internet.
Plenum & Plenum Problem, & Plenum-Rated Cables
Plenum: the space in the ceiling under the floors, in the walls, through which cable runs.
Plenum Problem: heat can melt PVC from cables, creating noxious fumes that could spread throughout the building.
Plenum-grade cabling: Cabling with a fire-retardant jacket
Crossover Cable
A standard UTP cable with one RJ-45 connector using T568A, the other using T568B.
Reverses the signal between sending & receiving wires (similar to a hub/switch)
Quick way to connect 2 computers directly.
Fiber Optic Cabling (General)
Uses light instead of electricity.
Immune to electrical problems.
Signals travel much farther than UTP (2000m+)
Half-duplex
2 types of light: Regular & Laser
Fiber Optic Connectors
ST Connector: Round
SC Connector: Square
LC Connector: Double square-shaped
(Designed to support two fiber cables in one to compensate for issue with half-duplexing)
Half-Duplex
Data flows only one way (hence the need for 2 cables in fiber optics)
Also, hence the use of the LC connector.
Network Fiber Optics (Light Type)
Network fiber optics use LED light signals.
Multimode Fiber Optic Cabling
Slower than single-mode.
Transmits multiple light signals at the same time.
Each signal uses different reflection angles
(Best for short distances; will disperse if too long)
600m max length (generally)
Single-Mode Fiber Optic Cabling
Faster than multimode
Use laser light: high transfer rates over long distances.
Rare, niche use.
Coaxial Cabling
Consists of a center cable (core) surrounded by insulation.
Covered with a shield of braided cable.
Core carries signal; shield eliminates interference.
Tops off at 100Mbps
RG-59
Coaxial Cabling Rating:
Low bandwidth & lower frequency applications
(Analog video & CCTV installations)
75 ohm impedance
Thinner than RG-6; doesn’t carry signal as far
RG-6
Coaxial Cabling Rating:
High-bandwidth & higher frequency applications
(Internet, cable TV, Satellite TV)
75 ohm impedance
Heavier gauge than RG-59
(Thicker insulation & better shielding)
Coaxial Connectors
BNC Connector:
Quarter-twist connector (uncommon)
F-Type Connector: Screw connector (common: cable modems/TVs)
LAN
Local Area Network:
Group of computers located physically close to one another (no more than a few hundred meters)
Almost always a broadcast domain.
Broadcast Domain
Group of computers connected by one or more switches.
Ethernet over Power (EoP)
Uses specialized bridges that transfer ethernet signal through the powerline.
Bridge
A device that connects dissimilar network technologies that transmit the same signal.
Connects two LANs and controls data flow between them.
Only has 2 ports, as opposed to a switch, which has many.
Structured Cabling
Cabling system by ANSI/TIA that give pro installers detailed standards on every standards on every aspect of a cabled network.
(type of cabling, running cable into walls, position of wall outlets, etc.)
Purpose of Structured Cabling
To create a safe, reliable cabling infrastructure for all devices that may need interconnection.
(Useful for telephone networks & video conferencing as well)
Qualities of Successful Cabling Networks (Three)
Telecommunications Room
Horizontal Cabling
Work Area
Telecommunications Room
One central location where all work areas come together (central cable location).
Utilize equipment racks, patch panels, & cables.
Equipment Racks
Central component of every telecommunications room. Provides a safe, stable platform for all different hardware components.
19 in wide (universal)
Height = U (1U, 2U, 4U) | U = 1.75in
Rack-mounted switches & rack-mounted servers exist
They utilize a UPS (Uninterruptible power supply)
Patch Panel
A box with a row of female connectors (ports) in the front, and permanent connections in the back.
AKA: 110 Block (110 Punchdown Block)
UTP cables connect using a punchdown tool
Punchdown block as small metal-lined grooves for the individual wires.
UTP patch panels have Cat ratings!
Patch Cables
Ethernet cables that connect the ports on a patch panel, to the switch.
Stranded cable, to tolerate more handling.
RJ-45 Crimping
Use crimping tool (RJ-45 Crimper w/wire strippers)
Cut the cable square using the crimpers
Strip off 1/2 in of plastic jacket from end of cable.
Slowly/carefully insert each individual wire into the correct location.
Insert crimp into crimper & press
install boot before crimping both ends
Use cable tester to verify proper connections
Horizontal Cabling & Run
Running all cables horizontally from the telecommunications room to workstations.
Run: Single piece of installed horizontal cabling.
The Work Area
The workstation receiving the signal coming from the telecommunications room.
Has a wall outlet that serves as the termination point for horizontal network cables.
Outlet consists of one/two female jacks for the cable.
The source of most failures (check first).
WAN (Wide Area Network)
A widespread group of computers connected using long-distance technology.
Connecting multiple smaller networks into a bigger network. (Turning LANs into a single WAN)
Requires a router for… routing.
Routing
Powerful addressing: address a frame so that it goes to a computer within LAN or another LAN within the same WAN.
Network Protocol Software
i.a.o
Takes incoming data received by the network card and keeps it organized.
Sends the data to the application that needs it.
Takes outgoing data from the application and hands it to the NIC to be sent out over the network.
TCP/IP
Transmission Control Protocol/Internet Protocol:
Primary protocol for most modern networks.
To access the internet, a computing device must have TCP/IP loaded and configured properly.
Purpose of Network Addresses
Uniquely identify the machine.
Locate the machine within a larger network.
IP Address
Identifies the node and the network on which the device resides.
(Identifies network ID & host ID)
Unique to each device
IPv4
Internet Protocol version 4:
Four sets of eight binary numbers (octets)
(AKA: dotted decimal notation)
Subnet Mask
NIC uses Subnet Mask to distinguish which part of the IP identifies the network ID, and which part identifies the host.
EX: 255.255.255.0
Network ID: 255s
Host ID: 0s
IP Conflict
Two computers have the same IP address and can’t talk to each other. Other computers won’t know where to send data.
Old Subnet Mask Class System
A = 255.0.0.0 B = 255.255.0.0 C = 255.255.255.0
CIDR
Classless Inter-Domain Routing:
Subnet mask is referred to by the number of 1s.
255.255.255.0 = /24 (twenty-four binary 1s)
How to create more host IDs with the subnet mask
- 255.240.0
- 11111111.11110000.00000000
Use a smaller number than 255 to add more 0s.
Router
Networking device that forwards data packets between computer networks.
Filters & forwards by IP address.
One port connects to LANs switch & receives an IP address that’s part of your network ID.
Other port connects to next network (usually ISP)
Default Gateway
The IP address of the LAN side of the router.
The address computers use to send data to anything outside your network ID.
DNS
Domain Name Service:
A service for registering IP addresses with “domain” names.
Today, most web servers host multiple sites under the same IP (helps for security).
DNS Server
Keep databases of IP addresses and their corresponding names.
DHCP
Dynamic Host Control Protocol:
Helps to obtain an IP address automatically.
DHCP server provides computer with all IP info it needs to get on a network.
DHCP Reservation
Network admins set up DHCP servers to save IP addresses for specific functions (servers, printers, etc.)
Static IP
A manually-assigned, fixed IP address.
UDP
User Datagram Protocol:
A connectionless protocol.
Works best when you have a lot of data to send that doesn’t need to be perfect or when systems are so close that there aren’t chances of a problem.
Ex: VoIP (Voice over IP)
Much faster than TCP, but prone to errors/imperfect data.
TCP
Transmission Control Protocol (Connection):
Gets an applications data from one machine to another reliably/completely.
Ping
2 Commands
TCP/IP Tool:
Provides a great way to see if you can talk to another system.
ping -t = ping continuously sends ping packets until you stop it with break command (CTRL-C)
ping -l = Enables you to specify how big a ping packet to send.
ipconfig/ifconfig
ipconfig (Windows) | ifconfig (Mac/Linux)
ipconfig /all = gives you a glance at network settings
Does little when using static IP.
(ipconfig /renew) + (ipconfig /release):
Renew/release IP address (with DHCP)
nslookup
Enables you to determine exactly what information the DNS server is giving you about a specific host name.
tracert/traceroute
tracert (Windows) | traceroute (Mac/Linux):
tracert/traceroute + IP
Describes the route from your machine to the destination machine.
Includes all devices the packet passes through.
How long each hop between devices takes.
Handy for troubleshooting bottlenecks.
Can help determine if a problem exists on a machine or router in control.
APIPA/zeroconf
Automatic Private IP Addressing (Windows)
zeroconf (Mac/Linux):
Automatically assigns IP to the system when client cannot obtain an IP address automatically.
Happens if system cannot contact DHCP server.
If using, system can only communicate with computers on the same subnet w/16-bit mask (169.254.x.y)
IPv6
Internet Protocol version 6 (128 bits):
Developed by IETF in order to compensate for the limited number of addresses with IPv4 (4 billion).
Ex: 2001:0000:0000:3210:0800:200c:00cf:1234
IPv6 Abbreviation
Leading 0s can be dropped from any group to abbreviate.
Can remove consecutive groups of 0s, leaving 2 colons. (Can only use ONCE)
Ex: fe80:0000:0000:0000:00cf:0000:ba98:1234
fe80::cf:0:ba98:1234
IPv6 Loopback Address
::1
A unicast localhost address.
IPv6 Prefix Lengths
Used to determine whether to send packets to a local MAC address or to the default gateway (internet).
Last 64 bits generated by NIC
(nothing longer than /64)
Global Unicast Address
A second IPv6 address, equivalent of IPv4 public address.
Computers need one to access the internet.
RS & RA
Router Solicitation:
When a computer is plugged into a network, the computer sends this packet to the router.
Uses a multicast address (no broadcast)
Router Advertisement:
The router hears this and responds with the network ID & subnet (prefix) & DNS server
Installing & Configuring a Wired Network
Three Main Steps
Connected NIC: The physical hardware that connects the computer system to the network media.
Properly configured IP addressing:
You device needs correct IP addressing for your network, either via DHCP or static.
Switch: Everything connects to a switch.
Installing NIC
Every modern desktop has built-in NIC.
Windows automatically installs the driver once detected.
Full-Duplex Mode (NIC)
NIC can send & receive data at the same time.
Autosensing: comes with a feature that can detect old devices that might need to run half-duplex mode.
Half-Duplex Mode (NIC)
The device can send & receive data, but not at the same time.
Adjust Duplex/Speed Manually
Control Panel > Network & Sharing > Change Adapter Settings
Right-click NIC & select properties > Configure > Advanced
Adjust the value on the right to match old device.
Link Lights
LED status indicators that give info about the state of NIC’s connection. (1-4 different link lights; any color)
Switches also have link lights.
If PC can’t access network, check link lights.
Properly functioning: steady light
Connection problem: flickering
Activity Light
Turns on when card detects network traffic.
Intermittent flickering when operating properly.
General NIC Light Concepts
Solid green: connectivity
Flashing green: intermittent connectivity
No green: no connectivity
Flashing amber: collisions on network (not always bad)
Wake-on-LAN
Waking up computers on a network from sleep while not being at their physical location.
Utilizes another PC on the network to send either a special pattern or magic packet. (sometimes in BIOS)
Manage Network Connections (Network & Sharing)
> Right-click NIC > Properties > Power Management
Check off “allow this device to wake the computer”
Unmanaged Switch
A smart, automatic device.
Devices plugged in will communicate via MAC addresses with no configuration needed.
Managed Switch
Offers a lot of features that modern networks use to provide added security/efficiency.
Utilize an IP address that one can use to configure the options/settings.
Support for VLANs (Virtual LAN)
NTFS Permissions
File/folder level permissions.
Defines what users can do with the resource.
Who can use & how they can use it
Non-NTFS Permissions
Default sharing wizard:
Read | Read/Write | Owner
Advanced Sharing:
Read | Change | Full Control
Sharing a folder on an NTFS drive
You must set both the network permissions and the NTFS permissions to let others access shared resources.
Network: share the resources
NTFS: what folks can do with the resource
Network > Full Control
NTFS > Control who & how
Network Organization: Workgroups
The most basic/simplistic of the three network organizations.
Every computer on network must be in same workgroup to share resources.
Username: Identification
Password: Authentication
Domains
A network organization that centralizes user accounts, passwords, and access to resources.
User can use domain account log in on any computer on the entire network. (Single Sign-On)
Domain Controller
Windows Server computer (authentication server)
Stores domain accounts.
Active Directory Domain
Domain controller that stores domain info, printer info, computer names, location info, and anything to define the network.
You log on directly to the domain (instead of the computer)
Ex: totalhome.local\Mike
Domain: totalhome.local
User: Mike
Active Directory Utility
4 Main Folders
Builtin (sic): All built-in domain groups are stored here.
Computers: Every system (servers/workstations) listed.
Domain Controllers: Lists all controllers
Users: All non-built-in users for domain
Domain Administration:
Logon/Login Scripts
A script that runs every time a user logs in.
Can create network shares, place an info box on screen, run special apps (ex: anti-malware), or pretty much anything you want.
Add path & name of script under user profile tab.
Maintaining Static Home Folders Across Network
2 concepts/terms
Roaming Profiles: A user logs on the domain, and the roaming profile applies to whichever computer the user logs on.
Folder Redirection: Admin specifies the location of users’ home folders, which are accessed from a remote server instead of local.
OU
Organizational Unit:
Containers that enable admins to organize users & computers by function, location, or permission.
Network Organization: Homegroups
Connects a group of computers using a common password (no special usernames needed) for file sharing.
Share LIBRARIES and not folders.
Tracing
Connect the tone generator to known end of cable in question.
Position probe next to the other end of each of the potentially correct cables.
Probe makes a sound when near the right cable.
The net Command
net view: CMD version of network
Returns a list of Windows computers on network.
“net view name1” = will show shares on specific machine
net use: CMD method for mapping shares
Mapping a drive = drive will show up in file explorer as a selectable resource
“net use x: \server1\research”
Maps drive X to Research share on SERVER1 computer.
The nbtstat Command
(NetBIOS over TCP/IP Statistics)
3 Main Commands
Old CMD utility that predates Windows.
Can provide insight when troubleshooting naming issues in small workgroups.
nbtstat -n (view computer’s NetBIOS name)
nbtstat -a 192.168.4.52 (Query remote machine by IP to find out NetBIOS name)
nbtstat -c (View all names that NetBIOS has in its local cache)
