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Networking Commands
Networking Commands Commands to check a server’s network: ip a (addresses), ss -tulnp (listening ports), ping , curl , nc . ss -tulnp is like a scan from the inside. Every listening port is a possible way in. A service on 0.0.0.0 is open to all. On 127.0.0.1 it is local only. “Ping fails, so the ser
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What it is
Commands to check a server’s network: ip a (addresses), ss -tulnp (listening ports), ping, curl, nc.
Why it matters for security
ss -tulnp is like a scan from the inside. Every listening port is a possible way in.
A service on 0.0.0.0 is open to all. On 127.0.0.1 it is local only.
Common mistake
“Ping fails, so the server is down.” Wrong. AWS security groups block ping by default.
Test a port with nc -zv IP 80 or curl -I.
| Command | Purpose | Example |
|---|---|---|
| ip addr (ip a) | Interfaces and IP addresses | ip -4 a |
| ip route | Routing table / default gateway | ip r |
| ss -tulnp | Listening TCP/UDP ports with process | sudo ss -tlnp |
| netstat -tulnp | Older equivalent of ss (package net-tools) | sudo netstat -tlnp |
| ping | Reachability (ICMP) | ping -c 4 google.com |
Learn more in the lesson: 6.7 Networking Commands