LLDP
Also called Link Layer Discovery Protocol, IEEE 802.1AB.
Devices announcing themselves to their directly connected neighbours — name, port, capabilities, and often PoE requirements. On a show network it is what turns "which switch port is this node on" from a cable-tracing job into a question the switch can answer.
Discovery, monitoring, configuration, backups, updates. Useful, and none of it has a deadline of its own.
What kills it. Nothing kills it. That is the problem: with no deadline it has no manners, and it will happily starve everything that does have one. Putting it on a show VLAN is the commonest self-inflicted wound in the industry.
Why this one, and not what the category suggests. Neighbour discovery, for the benefit of whoever has to draw the diagram later.
What goes wrong
Typical use
- Finding which port a device is plugged into without tracing the cable
- PoE power negotiation beyond the basic hardware classes
- Documenting an installed network from the switches rather than from memory
Sources
Known gaps on this entry: default_ports, first_published, implementations. If you can source one of them, that is a ten minute pull request.
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