Cisco Discovery Protocol
Last updated
Last updated
CDP is a Cisco proprietary protocol.
It is enabled on Cisco devices (routers, switches, firewalls, IP phones, etc) by default.
CDP messages are periodically sent to multicas MAC address 0100.0CCC.CCCC.
When a device receives a CDP message, it processes and discards the message. It does not forward it to other devices.
By default, CDP messages are sent once every 60 seconds.
By default, the CDP holdtime is 180 seconds. If a message isn't received from a neighbor for 180 seconds, the neighbor is removed from the CDP neighbor table.
CDPv2 messages are sent by default.
show command summaryShows basic information about CDP (timers, version).
Displays how many CDP messages have been sent and received.
Displays which interfaces CDP is enabled on.
Lists CDP neighbors and some basic information about each neighbor.
Lists each CDP neighbor with more detailed information.
Displays the same infor as above, but for the specified neighbor only.
CDP is globally enabled by default.
CDP is also enabled on each interface by default.
To enable/disable CDP globally: R1(config)# [no] cdp run
To enable/disable CDP on specific interfaces: R1(config-if)# [no] cdp enable
Configure the CDP timer: R1(config)# cdp timer <seconds>
Configure the CDP holdtime: R1(config)# cdp holdtime <seconds>
Enable/disable CDPv2: R1(config)# [no] cdp advertise-v2
