Further reading

• Guidance for Cisco IOS port utilization commands can be found through the Cisco support site:
  • CDP: https://www.cisco.com/c/en/us/support/docs/network-management/discovery-protocol-cdp/43485-cdponios43485.html

  • shutdown: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960/software/release/12-2_55_se/command/reference/2960_cr/cli3.html

  • port-security: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/25ew/configuration/guide/conf/port_sec.html

• Infosec Institute's guide to Nmap gives more detail on some of the other scan types. This can be accessed at https://resources.infosecinstitute.com/nmap/#gref.