0.4 Set up your machine (20 minutes)

Step 1 — Check what you have

Run each of these. You want a version number, not "command not found".

ping -V 2>/dev/null || ping -c1 127.0.0.1   # reachability test
traceroute --version 2>/dev/null || traceroute -V
dig -v                                       # DNS lookups
curl --version                               # HTTP client
ss -V 2>/dev/null || netstat --version       # socket list (Linux: ss)
tcpdump --version                            # packet capture
nc -h 2>&1 | head -2                         # netcat: manual connections
ip -V 2>/dev/null || ifconfig -h 2>&1|head -1

Step 2 — Install what's missing

macOS (most tools ship built in):

# Homebrew: https://brew.sh  (install it first if you don't have it)
brew install iproute2mac mtr bind    # 'ip' command, mtr, and dig/host
brew install --cask wireshark        # GUI packet analyser

ping, traceroute, netstat, tcpdump, nc, curl, dig are already there. macOS has netstat rather than ss.

Linux (Debian/Ubuntu):

sudo apt update
sudo apt install -y iproute2 iputils-ping traceroute mtr-tiny dnsutils \
                    curl netcat-openbsd tcpdump wireshark whois

Windows: the friendliest path is WSL2 (Windows Subsystem for Linux) — install Ubuntu from the Microsoft Store, then use the Linux commands above. Native Windows equivalents also exist: ping, tracert, nslookup, netstat -ano, curl, and Wireshark.

Step 3 — Let yourself capture packets

Packet capture needs privileges.

Linux — either use sudo tcpdump ..., or grant your user permission once:

sudo usermod -aG wireshark $USER      # then LOG OUT and back in

macOS — sudo tcpdump ... works. Wireshark will prompt to install ChmodBPF.

Test it:

sudo tcpdump -i any -c 5 -n

You should see five lines of traffic scroll past. If you see tcpdump: <interface>: You don't have permission to capture, fix privileges above.

Step 4 — Know your own network

Run this and save the output in notes.md — you'll refer to it constantly:

# Linux
ip -br addr ; echo ---- ; ip route ; echo ---- ; cat /etc/resolv.conf

# macOS
ifconfig | grep -A3 '^en' ; echo ---- ; netstat -rn | head -20
echo ---- ; scutil --dns | grep nameserver | head

You are looking for four things:

1. Your IP address (something like 192.168.1.50)
2. Your subnet mask / prefix (/24 or 255.255.255.0)
3. Your default gateway (usually 192.168.1.1)
4. Your DNS server(s)

Don't worry about what they mean yet — Parts 3 and 4 explain each one. But having your own numbers in front of you makes every example concrete.