Networking — cheat sheet¶

A one-page lookup for the commands used across this course. Grouped by task; the course pages cover the why behind each one — this page is just the what.

Addressing¶

Task	Command
Show this host's assigned addresses	`ip addr`
Show a single interface	`ip addr show <iface>`

Routing¶

Task	Command
Show the routing table	`ip route`
Show which route/gateway a destination would use	`ip route get <address>`
Trace the hop-by-hop path to a destination	`traceroute <host>` (or `tracepath <host>` / `mtr <host>` if `traceroute` isn't installed)

DNS¶

Task	Command
Resolve a name (shows which record type answered)	`dig <domain>`
Query a specific record type	`dig <domain> <type>` (e.g. `dig example.com MX`)
Simple lookup, alternative to `dig`	`nslookup <domain>`

Reachability & ports¶

Task	Command
Test network-layer (ICMP) reachability only	`ping <host>`
Test whether a specific TCP port is actually open	`nc -zv <host> <port>`
See what's listening locally	`ss -tlnp`

HTTP(S) & TLS¶

Task	Command
Full request trace — TCP connect, TLS negotiation, request/response headers	`curl -v <url>`
Same, discarding the response body (headers/timing only)	`curl -vo /dev/null <url>`

SSH¶

Task	Command
Open an interactive remote-shell session	`ssh <user>@<host>`
Run a single remote command without a full session	`ssh <user>@<host> <command>`

How this connects¶

The routing & gateways page covers reading the table above, the DNS page covers the resolution chain each record type answers, and the HTTP/TCP/SSH page covers mapping curl -v's own output to the TCP → TLS → HTTP boundary.