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Networking Fundamentals Cheat Sheet by

Networking basics and fundamentals

Network Types

LAN
Local Area Network
A single home or office network
WAN
Wide Area Network
Linking multiple resources or LANs - Multiple office networks
MAN
Metrop­olitan Area Network
Linking multiple LANs - SOC, school networks, city networks

Network Topologies

Bus Topology
All computers are connected to a single cable
Antiquated process - still used in broadcast media
Star Topology
Each node is connected to a switch
Most common network setup you will see
Ring Topology
Each node is connected to one other. Reduces chances of packet collision
Rarely seen outside of a MAN or ISP datace­nte­r-t­o-d­ata­center connection
Mesh Topology
Each node has an indepe­ndent connection to every other node on the network
Used by MSPs and ISPs for highly­-av­ailable and fault tolerant networks.

Network Cables - Copper

Cable Type
Max data transfer speed
Max Operating Length
CAT5
100 Mbps
100 Meters
CAT5e
1 Gbps
100 Meters
CAT6
10 Gbps
55 Meters
CAT6a
10 Gbps
100 Meters
CAT7
10 Gbps
100 Meters
CAT8
40 Gbps
30 Meters

Network Cables - Fiber

Cable Type
Max Speed/­Dis­tance
Typical Use
OM1 - Orange Jacket
10 Gbps/33 Meters
100 Mbps Ethernet
OM2 - Orange Jacket
10 Gbps/82 Meters
1 Gbps Ethernet
OM3 - Aqua Jacket
10 Gbps/300 Meters
10 Gbps Ethernet
OM4 - Aqua Jacket
10 Gbps/400 Meters
100 Gbps Ethernet @ 150 meters
OM5 - Green Jacket
10 Gbps/400 Meters
Improv­ements on OM4. It breaks down light wavele­ngths more effici­ently.
OS1 - Yellow Jacket
up to 100 Gbps/10 km
Single mode fiber for connecting indoor nodes. Used in fiber internet connec­tions and datace­nters.
OS2 - Yellow Jacket
up to 100 Gbps/200 km
Single mode fiber for connecting infras­tru­cture outdoors. Used for MANs, ISPs, or MSPs.
 

7 Layer OSI Model

Layer
Typical Use
Protocols
Applic­ation
End User Layer
HTTP, FTP, SSH, DNS
Presen­tation
Syntax Layer
SSL, SSH, IMAP, MPEG, JPEG
Session
Sync & Send Layer
APIs, Sockets
Transport
End-to-end Connec­tions
TCP, UDP
Network
Packets
IP, ICMP, IPSec, IGMP
Data Link
Frames
Ethernet, PPP, Switch
Physical
Physical Structure
Fiber, Access Points, Copper Cabling

OSI Troubl­esh­ooting

Layer
Command
Purpose
Physical
 
ip -br -c link
Is your physical interface up? Gives you detailed inform­ation on your NICs and virtual NICs.
Data Link
 
ip neighbor show
Displays the Address Resolution Protocol (ARP) table. Shows the IP and MAC addresses of computers you can reach on the network.
Network
 
ip -br -c address show
or 
ip -br -c a'
Displays your network cards, their connection status, the IP address and CIDR. Make sure you have a valid IP address on your LAN NIC.
  
ping <we­bsite or IP addres­s>
Ping the device you're trying to connect to, or ping a commonly used server like Google's DNS (8.8.8.8) .
  
traceroute <we­bsite or IP addres­s>
Sends a packet out to a destin­ation using Time to Live (TTL). The end result is a list of routers that the packet interacted with on the way to the destin­ation
  
ns lookup <we­bsite name>
Checks recognized DNS entries on your server. Make sure the IPs match up with results from ping
Transport
 
ss -tunlp4
Socket Statistics gives you a list of connec­tions and ports on your server. Use it to make sure you are able to connect to certain devices
-t  ­ ­ ­ Show TCP ports
-u  ­ ­ ­ Show UDP ports
-n  ­ ­ ­ Do not try to resolve hostnames
-l  ­ ­ ­ Show only listening ports
-p  ­ ­ ­ Show processes that are using a particular socket
-4  ­ ­ ­ Only show IPv4 sockets
Session
SSH or RTP
Get a device to accept your SSH session or initialize an RTP session from a camera. Keep in mind, RTP is different from RTSP.
Presentation
HTML, RTSP
Connect to a camera's webpage, or query a camera stream through VLC.
Application
Using the program
Can you interact with a webpage? Can you view DS logs once it's running? Good! Then you've confirmed the Applic­ation is up and running.

Network Hardware

 
Network Border
Firewall
Prevents unauth­orized access into a LAN.
Reside­ntial Gateway
"The wifi" - That little black box that people have near their TVs that they call: the internet. This will be the handoff from an ISP to your LAN or firewall.

Network Core
Gateway
Provides compat­ibility between different networks.
Router
Forwards data packets between different networks. They "­direct traffi­c" typically received from outside networks.
Switch
Connects devices together by using packet switching. Used for internal traffic.
Wireless Access Point
The Wifi! This allows wireless devices to connect to a network rather than plugging into a switch directly.
Patch Panel
You plug your computer into a wall port. The wall port is connected to a patch panel. The patch panel connects to the switch. This prevents a tech from running new cables through a wall every time a computer joins the network.

Network End Stations
Network Interface Controller (NIC)
The ethernet jack on a computer.
Wireless Network Interface Controller
Same thing as a NIC, but it uses radio waves to connect to an access point instead of a cable.
 

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  • Published: 27th May, 2021
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