Networking basics and fundamentals
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LAN
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Local Area Network
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A single home or office network
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WAN
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Wide Area Network
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Linking multiple resources or LANs - Multiple office networks
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MAN
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Metropolitan Area Network
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Linking multiple LANs - SOC, school networks, city networks
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Bus Topology
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All computers are connected to a single cable
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Antiquated process - still used in broadcast media
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Star Topology
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Each node is connected to a switch
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Most common network setup you will see
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Ring Topology
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Each node is connected to one other. Reduces chances of packet collision
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Rarely seen outside of a MAN or ISP datacenter-to-datacenter connection
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Mesh Topology
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Each node has an independent connection to every other node on the network
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Used by MSPs and ISPs for highly-available and fault tolerant networks.
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Cable Type
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Max data transfer speed
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Max Operating Length
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CAT5
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100 Mbps
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100 Meters
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CAT5e
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1 Gbps
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100 Meters
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CAT6
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10 Gbps
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55 Meters
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CAT6a
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10 Gbps
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100 Meters
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CAT7
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10 Gbps
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100 Meters
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CAT8
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40 Gbps
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30 Meters
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Cable Type
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Max Speed/Distance
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Typical Use
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OM1 - Orange Jacket
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10 Gbps/33 Meters
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100 Mbps Ethernet
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OM2 - Orange Jacket
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10 Gbps/82 Meters
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1 Gbps Ethernet
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OM3 - Aqua Jacket
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10 Gbps/300 Meters
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10 Gbps Ethernet
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OM4 - Aqua Jacket
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10 Gbps/400 Meters
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100 Gbps Ethernet @ 150 meters
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OM5 - Green Jacket
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10 Gbps/400 Meters
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Improvements on OM4. It breaks down light wavelengths more efficiently.
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OS1 - Yellow Jacket
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up to 100 Gbps/10 km
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Single mode fiber for connecting indoor nodes. Used in fiber internet connections and datacenters.
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OS2 - Yellow Jacket
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up to 100 Gbps/200 km
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Single mode fiber for connecting infrastructure outdoors. Used for MANs, ISPs, or MSPs.
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Layer
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Typical Use
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Protocols
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Application
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End User Layer
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HTTP, FTP, SSH, DNS
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Presentation
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Syntax Layer
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SSL, SSH, IMAP, MPEG, JPEG
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Session
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Sync & Send Layer
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APIs, Sockets
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Transport
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End-to-end Connections
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TCP, UDP
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Network
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Packets
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IP, ICMP, IPSec, IGMP
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Data Link
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Frames
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Ethernet, PPP, Switch
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Physical
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Physical Structure
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Fiber, Access Points, Copper Cabling
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Layer
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Command
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Purpose
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Physical
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ip -br -c link |
Is your physical interface up? Gives you detailed information on your NICs and virtual NICs.
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Data Link
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ip neighbor show |
Displays the Address Resolution Protocol (ARP) table. Shows the IP and MAC addresses of computers you can reach on the network.
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Network
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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.
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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) .
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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
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ns lookup <website name> |
Checks recognized DNS entries on your server. Make sure the IPs match up with results from ping
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Transport
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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 |
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Session
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SSH or RTP
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Get a device to accept your SSH session or initialize an RTP session from a camera. Keep in mind, RTP is different from RTSP.
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Presentation
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HTML, RTSP
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Connect to a camera's webpage, or query a camera stream through VLC.
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Application
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Using the program
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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.
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Network Border
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Firewall
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Prevents unauthorized access into a LAN.
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Residential Gateway
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"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.
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Network Core
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Gateway
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Provides compatibility between different networks.
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Router
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Forwards data packets between different networks. They "direct traffic" typically received from outside networks.
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Switch
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Connects devices together by using packet switching. Used for internal traffic.
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Wireless Access Point
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The Wifi! This allows wireless devices to connect to a network rather than plugging into a switch directly.
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Patch Panel
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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.
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Network End Stations
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Network Interface Controller (NIC)
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The ethernet jack on a computer.
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Wireless Network Interface Controller
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Same thing as a NIC, but it uses radio waves to connect to an access point instead of a cable.
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