Ports and Networks

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September 15, 2022 (last updated January 12, 2023)

nmap and net-tools contain a collection of tools and functionality to let you explore your network.

Network Scan

  1. ifconfig will tell you your IP address and your subnet.
  2. sudo nmap -sn [CIDR] will tell you the other devices on your network, their IP address, and other details when available.
    • -sn : "Ping Scan - disable port scan". This speeds up the request by disabling per-discovered-device port scanning, which can take a while.
    • CIDR : Classless Inter-Domain Routing. See Wiki. It specifies a range of network ports to scan over.
    • An example: sudo nmap -sn, will scan
  3. For a scan with additional information per discovered device, run sudo nmap -A -T4 CIDR
    • -A : "Enable OS detection, version detection, script scanning, and traceroute"
    • -T : "Set timing template (higher is faster)"

Port Scan

  • nmap [IP Address]
    • nmap port scanning tutorial
    • It will, among othe things, scan the 1000 most popular ports and report back whether or not they are open, and which services are available/listening on those ports.
    • nmap -p 80[,443,...] example.com will scan a specific port

Common Ports and Services

  • :22/tcp - ssh. Allows remote connection.
  • :23/tcp - telnet. It's its own thing :D.
  • :53/tcp - domain. DNS server. Routers will commonly open this port.
  • :80/tcp - http. Any web browser can display comms.
  • :554/tcp - rtsp. Real Time Streaming Protocol. E.g., used by IP cameras for streaming videos. VLC video player can display RTSP streams.
  • :9010/tcp - sdr. Software Defined Radio? I see it on IP video cameras.