IP Addressing Basics

Core Idea

An IP address names a network interface location. DNS names such as lf2607.kolamayermakers.org are human-readable labels that resolve to addresses. Ports identify a service on an address.

Commands To Try

host lf2607.kolamayermakers.org
curl -I https://lf2607.kolamayermakers.org/~username/

host gives a compact DNS answer. dig gives a fuller DNS answer. curl tests whether an HTTP service responds after DNS and connection setup.

Address, Port, Protocol

https://lf2607.kolamayermakers.org/~username/
|     |                                             |
scheme host name                                     path

https implies TCP port 443 unless another port is written explicitly. Your user-managed service uses a local high port behind the public reverse proxy.

IPv4 And IPv6

• IPv4 addresses look like 203.0.113.10.
• IPv6 addresses look like 2001:db8::10.
• DNS can return either or both.
• A service can work on one address family and fail on another if routing or firewall rules differ.

Common Confusions

• DNS success does not prove the web service works.
• Ping failure does not prove HTTP failure; ICMP can be blocked.
• localhost and 127.0.0.1 mean the same machine from the point of view of the process running the command.
• A port can be open locally but unreachable publicly if no proxy or firewall path points to it.

Proof Check

Use host, then curl -I, and explain which command tested name resolution and which tested HTTP.

Docs Pointers

• Run man host, man dig, and man curl.
• Read Cloudflare Learning Center: What is DNS?.
• Read MDN: What is a URL?.
• Read IP Networking for the broader layered debugging model.
• Read DNS when you want record types and resolver behavior.
• Read ICMP when you want to understand what ping proves and does not prove.