3.6 Cisco Discovery Protocol

Question 1

What is CDP?

Answer 1

Cisco Discovery Protocol (CDP) is a layer 2 (Data Link) protocol that runs on all Cisco devices. CDP broadcasts periodic advertisements.

Question 2

When should you disable CDP?

Answer 2

On routers on the edge of the network and user facing interfaces

Question 3

Router(config)#show cdp

Answer 3

Checks the status of CDP

Question 4

Router(config)#no cdp run

Answer 4

Disables CDP for all interfaces on a device

Question 5

Router(config)#cdp run

Answer 5

Enables CDP for all interfaces on a device

Question 6

Router(config)#no cdp enable

Answer 6

Disables CDP on that interface, but keeps CDP enabled for the device.

Question 7

Router(config)#cdp enable

Answer 7

Enables CDP on that interface.

Question 8

Router#show cdp neighbors

Answer 8

Checks for the status of CDP and shows a list of neighboring devices.

Question 9

What details does the command show cdp neighbors show

Answer 9

Device identifier – provides the host name of the neighboring device
Port identifiers – provides the name of the local and remote port
Capabilities list – indicates whether the device is a switch or a router
Platform – indicates the hardware platform of the device

Question 10

Router#show cdp neighbors detail

Answer 10

Provides the same information as show cdp neighbors as well as additional information such as IP address and IOS version.

Question 11

Router#show cdp interface

Answer 11

Provides the full CDP configuration for the interface.

Question 12

Router#show ip interface brief

Answer 12

Provides the abbreviated CDP configuration for the interface.

Question 13

Router(config)#lldp run

Answer 13

Enables LLDP globally on the router.

Question 14

Router(config)#no lldp run

Answer 14

Disables LLDP on a router and prevents the router from exchanging LLDP packets.

Question 15

Router(config-if)#lldp transmit

Answer 15

Enables the interface to send LLDP information.

Question 16

Router(config-if)#no lldp transmit

Answer 16

Disables the interface from sending LLDP information.

Question 17

Router(config-if)#lldp receive

Answer 17

Enables the interface to receive LLDP information.

Question 18

Router(config-if)#no lldp receive

Answer 18

Disables the interface from receiving LLDP information.

Question 19

Router#show lldp

Answer 19

Displays LLDP information, including frequency of transmissions, hold time for packets to be sent, and the delay time for LLDP initialization on an interface.

Question 20

Router#show lldp interface

Answer 20

Displays information about interfaces that have LLDP enabled, including transmit and receive configuration, as well as the current state.

Question 21

Router#show lldp neighbors

Answer 21

Displays information about all neighboring Cisco devices, including:
Device ID
Local interface
Holdtime
Capability
Port ID

Question 22

Router#show lldp neighbors detail

Answer 22

In addition to displaying all the same information as the show lldp neighbors command, it also displays the following:
Physical media information and capabilities
A description of the neighbor
Software version

Question 23

Router#show lldp entry

Answer 23

Displays information about all neighbors similar to the show lldp neighbors detail command.

Question 24

Router#show lldp entry neighbor_name

Answer 24

Displays similar information for the specified LLDP neighbor.

Question 25

Router#show lldp traffic

Answer 25

Shows the current state of LLDP traffic, including the number of frames in and out, the number of dropped frames, and the number of Type-Length-Values (TLVs) discarded or un-recognized.

Question 26

Router#clear lldp counters

Answer 26

Resets traffic counters to 0.

Question 27

Router#show lldp errors

Answer 27

Shows lldp error counters.

Question 28

Router(config)#lldp holdtime [10-255]

Answer 28

Specifies the amount of time that information in a packet is still valid. The default is 120 seconds. Use the no lldp holdtime command to reset the value to its default.

Question 29

Router(config)#lldp timer [5-254]

Answer 29

Specifies how often LLDP packets are exchanged. The default is 30 seconds. Use the no lldp timer command to reset the value to its default.

Question 30

What does the protocol LLDP do

Answer 30

allows a network engineer to discover non-Cisco devices in the network