CDP vs LLDP
Both CDP and LLDP are Layer 2 protocols that let a device discover its directly-connected neighbors — IDs, IPs, platforms and ports. The difference: CDP is Cisco-proprietary, while LLDP is the open IEEE standard that works across vendors.
Side by side
| CDP | LLDP | |
|---|---|---|
| Standard | Cisco proprietary | IEEE 802.1AB (open) |
| Works with | Cisco only | Any vendor |
| Default | On (Cisco devices) | Often off — enable it |
| Info shown | Neighbor ID, IP, platform, port | Same, vendor-neutral |
When to use which
On an all-Cisco network, CDP is on by default and gives an instant map with show cdp neighbors. In a mixed-vendor network, use LLDP — enable with lldp run, read with show lldp neighbors. Both are invaluable for documenting and troubleshooting what's plugged in where.
Security note
Discovery protocols advertise device details, so disable them on ports facing untrusted networks to avoid leaking topology information.
Frequently asked questions
What is the difference between CDP and LLDP?
CDP is Cisco-proprietary and on by default on Cisco devices; LLDP is the open IEEE 802.1AB standard that works across all vendors. Both discover directly-connected neighbors at Layer 2.
Is LLDP better than CDP?
LLDP is more versatile because it is vendor-neutral. On an all-Cisco network CDP works out of the box; in mixed environments LLDP is the right choice.
How do I see CDP neighbors?
Use show cdp neighbors (add detail for IP and version). For LLDP, enable it with lldp run and use show lldp neighbors.
Should I disable CDP/LLDP?
Disable them on ports facing untrusted networks or end users, since they advertise device details an attacker could use to map your network.
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