Most people scan TCP, get their results in seconds, and stop there. But a huge amount of what runs on a real network lives on UDP: DNS, DHCP, SNMP, NTP, TFTP, IKE. If you only ever scan TCP, you are
Version detection tells you what software a port is running. OS detection (-O) tries to answer a different question: what operating system is the whole host running, even on ports that give nothing away. It does this without logging in
A port number tells you almost nothing on its own. "Port 80 open" could be nginx, Apache, an embedded management interface, or a printer's web UI. "Port 22 open" could be OpenSSH, a Cisco
Nmap does not have one way to scan a TCP port, it has a whole family of them, and each one sets different flags to provoke a different reaction from the target. Knowing which scan type to reach for is
Once you know which hosts are alive, the real work is finding out what each one is listening on. Port scanning is how you build a service inventory, confirm a firewall change did what you expected, and catch the forgotten
Before you scan a single port, you need to know which addresses are actually alive. Blasting a full port scan at every host in a /24 wastes time on dead space and lights up any IDS in the path. Host
PortFast is a small spanning tree feature with an outsized practical effect: it is the difference between a host getting an IP address the instant it plugs in and a host sitting dark for thirty seconds while STP makes up
The native VLAN is one of those concepts that seems trivial - it is "the untagged VLAN on a trunk" - right up until a mismatch breaks a link, or a double-tagging attack hops a VLAN you thought was
CML 2.10 shows the Docker node definitions but no image definitions. Here is how to install the container images (net-tools, nginx, Snort, TACACS+, Splunk and more) from Cockpit.
Still worth it for most people, with one big caveat. The honest take on the 2026 to 2027 exam change, what the cert actually gets you, and the AI question.
OSPF is a link-state protocol, and the "link state" it routes on is a database. Link-state advertisements, or LSAs, are the individual records in that database. Before you can make sense of LSA types, areas, or