LLDP versus CDP

LLDP (Link Layer Discovery Protocol) and CDP (Cisco Discovery Protocol) are two neighbour discovery protocols used in computer networks. These protocols have some similar and different characteristics. Both LLDP and CDP are layer 2 (data-link layer) protocols. They are both used to discover directly connected other devices in the network. How about differences? What are the differences between LLDP and CDP? Here is the comparison of these neighbor discovery protocols.

LLDP vs CDP

When we compare LLDP and CDP, the first important difference is about standardization. LLDP is a standard based neighbor discovery protocol used by all manufacturers. On the other hand, CDP is a vendor specific protocol. In other words, CDP is Cisco proprietary protocol.

LLDP is defined as IEEE 802.1AB standard.

With LLDP we discover all the directly connected network devices. Here, device name, capabilities, port IDs are shared. CDP discovers only directly connected Cisco devices. Here device information such as IOS version, IP address and capabilities are shared. Because of supporting by all vendors, LLDP is used mostly in the networks.

Here, both protocols have advantages. The key point of Cisco Discovery Protocol is this: CDP provides detailed information about Cisco devices. On the other hand, LLDP is an interoperable protocol that can discover not only Cisco but also other vendor devices.  But LLDP (Link Layer Discovery Protocol) gets, not much details like CDP.

Below, you can find a comparison table for LLDP and CDP.

Frequently Asked Question on LLDP and CDP

Can LLDP and CDP run on the same Cisco device?

Yes, both protocols can run simultaneously without conflict. LLDP is often used for multi-vendor interoperability, while CDP is used for Cisco-specific details.

In Which layer do LLDP and CDP operate?

Both LLDP and CDP operate at Layer 2 (Data Link Layer) of OSI model.

Which neighbor discovery protocol provides more detailed information?

CDP provides detailed information such as IOS version, IP address, and device capabilities for Cisco devices. On the other hand, Link Layer Discovery Protocol provides basic device info across vendors.

How do I verify LLDP neighbors on a Cisco switch?

We can use lldp commands to verify lldp neighbors on Cisco devices. Here, “show lldp neighbors” and “show lldp neighbors detail” are good commands.

What Cisco commands can I use to check CDP neighbors?

To check CDP neighbors you can use “show cdp neighbors”, “show cdp neighbors detail” and “show cdp traffic” commands on Cisco devices.

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