CCNA: CDP/LLDP

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Description:

Cisco Discovery Protocol (proprietary) runs only on Cisco devices; it allows you to gather information about other routers and switches. It is enabled by default. It can also be a very useful command to use while troubleshooting to see which devices are directly connected to the device you are connected to.

To disable CDP For the whole switch:

Router(config)#no cdp run

To disable CDP for an interface:

Router(config-if)#no cdp enable

Show Commands:

show cdp
show cdp neighbors
show cdp neighbors detail
show cdp entry

Open source CDP = LLDP

To support non-Cisco devices and to allow for interoperability between other devices, the switch supports the IEEE 802.1AB LLDP. LLDP is a neighbor discovery protocol that is used for network devices to advertise information about themselves to other devices on the network. This protocol runs over the data-link layer, which allows two systems running different network layer protocols to learn about each other.
LLDP supports a set of attributes that it uses to discover neighbor devices. These attributes contain type, length, and value descriptions and are referred to as TLVs. LLDP supported devices can use TLVs to receive and send information to their neighbors. Details such as configuration information, device capabilities, and device identity can be advertised using this protocol.
LLDP is disabled by default

To Enable LLDP globally:

config t
lldp run
end

To Enable LLDP per interface:

config t
int fa0/0
lldp transmit
lldp receive
end
copy run start

LLDP Commands:

clear lldp counters
clear lldp table
show lldp
show lldp errors

 

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