Lesson 1 of 5
CDP and LLDP Discovery
Lab Objectives
- Use CDP (Cisco Discovery Protocol) and LLDP (Link Layer Discovery Protocol) to discover directly connected neighboring devices.
- Compare the outputs and behavior of CDP vs LLDP and understand when to use each in production networks.
- Verify neighbor information using show commands and interpret the details (IP, platform, local/remote interfaces, capabilities).
Topology and device information are included below so you can perform the lab against the exact interfaces and IPs shown.
Tip: Think of CDP and LLDP as "hello notes" that network devices leave on the wire describing themselves — like a business card. These protocols help you map topology without walking the rack.
ASCII Topology (use this EXACT topology)
[Internet]
203.0.113.1
|
R1 (Gateway)
Gi0/0: 10.10.10.1
Gi0/1: 10.10.20.1
Gi0/2: 10.10.30.1
/ | \
R2 R3 R4
Gi0/0: 10.10.10.2 | Gi0/0: 10.10.30.2
Gi0/1: 10.10.40.1 |
/ \ |
S1 S2 S3
/ \ | /
PC1 PC2 PC3 PC4 PC5
Device Table
| Device | Role |
|---|---|
| R1 | Central router / gateway |
| R2 | Router connected to S1 |
| R3 | Router connected to S2 |
| R4 | Router connected to S3 |
| S1 | Access switch (connects PC1, PC2) |
| S2 | Access switch (connects PC3) |
| S3 | Access switch (connects PC4, PC5) |
| PC1-5 | Hosts |
IP Addressing
| Link / VLAN | Network | Device Interface | IP Address |
|---|---|---|---|
| R1-R2 link | 10.10.10.0/24 | R1 Gi0/0 | 10.10.10.1 |
| R2 Gi0/0 | 10.10.10.2 | ||
| R1-R3 link | 10.10.20.0/24 | R1 Gi0/1 | 10.10.20.1 |
| R1-R4 link | 10.10.30.0/24 | R1 Gi0/2 | 10.10.30.1 |
| R4 Gi0/0 | 10.10.30.2 | ||
| R2-S1 link | 10.10.40.0/24 | R2 Gi0/1 | 10.10.40.1 |
| VLAN 10 (Sales) | 192.168.1.0/24 | Access ports on S1 | PCs in Sales |
| VLAN 20 (Engineering) | 192.168.2.0/24 | Access ports on S2 | PCs in Eng |
| VLAN 30 (Management) | 192.168.3.0/24 | Access ports on S3 | Management PCs |
| Internet sim | 203.0.113.0/24 | R1 to Internet | 203.0.113.1 (sim) |
Important: Use the exact IPs and interface names above when you run commands or interpret outputs.
Lab Tasks (Try It Yourself First!)
Complete these tasks WITHOUT looking at the solution below. Use
?andshowcommands to figure it out.
Task 1: Enable CDP Globally and Verify Neighbors
Enable CDP globally on the routers and switches (if it is disabled), then use show commands to list directly connected neighbors for R1 and S1. Verify neighbor IP addresses and interfaces.
Task 2: Enable LLDP and Verify Neighbors
Enable LLDP globally on the same devices, ensure interfaces are allowed to transmit and receive LLDP, and use show commands to display LLDP neighbor information for R1 and S2.
Task 3: Compare CDP vs LLDP Outputs
Collect detailed neighbor outputs (detail) for CDP and LLDP on R1 and explain differences in fields (for example, management IP presence and vendor-specific fields). Note which protocol is proprietary and which is standards-based.
Think About It: Why might a network operator prefer LLDP over CDP (or vice versa) in an environment with multi-vendor switches? Consider security and interoperability.
Lab Solution
Task 1 Solution: Enable CDP Globally and Verify Neighbors
What we are doing: CDP is Cisco’s proprietary discovery protocol. We enable it so devices advertise their identity, capabilities, and connecting ports. This helps build a quick topology map. In production, CDP is useful for Cisco-only networks for automated inventory and troubleshooting.
R1# configure terminal
R1(config)# cdp run
R1(config)# end
S1# configure terminal
S1(config)# cdp run
S1(config)# end
What these commands do and why they matter:
configure terminal— enters global configuration mode so we can change global protocol settings.cdp run— enables CDP globally on the device so all capable interfaces will transmit CDP advertisements. This matters because without it the device will not announce or learn neighbor info via CDP.
Verify:
R1# show cdp neighbors
Device ID Local Intrfce Holdtme Capability Platform Port ID
R2 GigabitEthernet0/0 131 R S I ISR4321 GigabitEthernet0/0
R3 GigabitEthernet0/1 131 R S I ISR4321 GigabitEthernet0/0
R4 GigabitEthernet0/2 131 R S I ISR4321 GigabitEthernet0/0
Explanation of verify output:
Device ID— remote device hostname (R2, R3, R4).Local Intrfce— local interface on R1 where the neighbor was learned.Holdtme— seconds remaining before the entry times out (CDP default hello 60s, holdtime default 180s; the dynamic field shown reflects current timer).Capability— device function (R=Router, S=Switch, I=IGMP capable).PlatformandPort ID— remote platform and remote port.
S1# show cdp neighbors detail
Device ID: R2
Entry address(es):
IP address: 10.10.10.2
Platform: ISR4321, Capabilities: Router Switch IGMP
Interface: GigabitEthernet0/1, Port ID (outgoing port): GigabitEthernet0/0
Holdtime : 174 sec
Version :
Cisco IOS XE Software, Version 16.9.3
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cisco
R1# configure terminal
R1(config)# lldp run
R1(config)# end
S2# configure terminal
S2(config)# lldp run
S2(config)# interface GigabitEthernet0/1
S2(config-if)# lldp transmit
S2(config-if)# lldp receive
S2(config-if)# end
What these commands do and why they matter:
lldp run— enables LLDP globally.interface ...followed bylldp transmit/lldp receive— ensures that specific interfaces both send and accept LLDP frames. Some deployments disable either transmit or receive for security or policy reasons.
Verify LLDP:
R1# show lldp neighbors
Capability codes:
(R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device
Device ID Local Intf Port ID
R2 Gi0/0 Gi0/0
R3 Gi0/1 Gi0/0
R4 Gi0/2 Gi0/0
R1# show lldp neighbors detail
Local Intf: GigabitEthernet0/0
Chassis id: 00:1a:2b:3c:4d:5e
Port id: GigabitEthernet0/0
Port Description: GigabitEthernet0/0
System Name: R2
System Description: Cisco IOS XE Software, Version 16.9.3
Management Addresses:
IP: 10.10.10.2
Time remaining: 100 seconds
<div class="topology-diagram">
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</div>
cisco
R1# show cdp neighbors detail
[output shown earlier for CDP with Version and Platform fields]
R1# show lldp neighbors detail
[output shown earlier for LLDP with Chassis id and Management Addresses]
<div class="topology-diagram">
<img src="data:image/svg+xml;base64,<?plantuml 1.2026.1?><svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" contentStyleType="text/css" data-diagram-type="DESCRIPTION" height="522px" preserveAspectRatio="none" style="width:360px;height:522px;background:#FAFAFA;" version="1.1" viewBox="0 0 360 522" width="360px" zoomAndPan="magnify"><title>Lab 63: Device Management &amp; Monitoring</title><defs/><g><rect fill="#FAFAFA" height="522" style="stroke:none;stroke-width:1;" width="360" x="0" y="0"/><g class="title" data-source-line="8"><text fill="#000000" font-family="sans-serif" font-size="14" font-weight="bold" lengthAdjust="spacing" textLength="332.2539" x="10" y="22.9951">Lab 63: Device Management &amp; Monitoring</text></g><!--cluster Lab Modules--><g class="cluster" data-qualified-name="Lab Modules" data-source-line="10" id="ent0002"><path d="M46.127,43.2969 L146.5557,43.2969 A3.75,3.75 0 0 1 149.0557,45.7969 L156.0557,65.5938 L319.127,65.5938 A2.5,2.5 0 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</div>
cisco
R2# show running-config interface GigabitEthernet0/0
interface GigabitEthernet0/0
no lldp transmit
no lldp receive
R2# configure terminal
R2(config)# interface GigabitEthernet0/0
R2(config-if)# lldp transmit
R2(config-if)# lldp receive
R2(config-if)# end
R1# show lldp neighbors
Device ID Local Intf Port ID
R2 Gi0/0 Gi0/0
Why this fixes it:
- If
no lldp transmitorno lldp receiveis configured, the interface will not send or accept LLDP frames, preventing neighbor discovery. Enabling both allows R2 to advertise and receive LLDP frames.
Verification Checklist
- CDP enabled globally on routers and switches (
cdp run). - LLDP enabled globally on devices that should advertise (
lldp run). -
show cdp neighborsandshow lldp neighborsshow expected neighboring devices on R1. -
show cdp neighbors detail/show lldp neighbors detaildisplay management IPs for neighbors.
Common Mistakes
| Symptom | Cause | Fix |
|---|---|---|
| No CDP neighbors shown | CDP disabled globally (no cdp run) | Enable with cdp run |
| LLDP shows fewer neighbors than CDP | Per-interface LLDP transmit/receive disabled | On interface: lldp transmit and lldp receive |
| Neighbor shows but no IP in CDP/LLDP detail | Device may not advertise management address | Ensure the neighbor has a management IP configured and advertises it (e.g., use proper mgmt interface configs) |
| Unexpected vendor reported | Device may rewrite system name or use generic chassis ID | Check show platform and show version on neighbor for platform confirmation |
Warning: Discovery protocols reveal topology and device details. On Internet-facing or untrusted ports, disable them or apply filters.
Challenge Task
Configure S1, S2, and S3 so that:
- CDP is enabled only on internal-facing ports (toward routers) but disabled on access ports to PCs.
- LLDP is enabled globally and set on all switch-to-switch and switch-to-router links, but disabled for PC access ports.
Goal: Produce a
show cdp neighborsandshow lldp neighborsfrom each switch that only shows upstream infrastructure devices (no PC entries). No step-by-step instructions — design and implement the interface-level settings yourself.
Final thought: Knowing both CDP and LLDP—and when to use or limit them—is a basic but critical skill for network mapping, troubleshooting, and secure design in production environments.