Discovery Protocols

Nmap is a complex app that needs a computer to run
Switch, router, and access point appliances can run simpler discovery protocols to identify other devices on the local network

Cisco Discovery Protocol

Cisco Discovery Protocol (CDP) is a proprietary protocol used by Cisco network appliances to discover layer 2 adjacent devices or neighbors.

runs by default on all Cisco switch, router, and access point hardware
uses Data Link layer multicast to send status announcements over local interfaces
- every 60 seconds
- uses address 01:00:0c:cc:cc:cc
- each device keeps a cache table of the data compiled from announcements received
show cdp neighbors reports information from the CDP cache
- reports ID/host name, IOS version, interface addresses and statistics, VLAN information, and PoE usage

Link Layer Discovery Protocol (LLDP) is a standards-based protocol used by network appliances to discover layer 2 adjacent devices or neighbors.