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Objective 2.3

200-301

Configure and verify Layer 2 discovery protocols (Cisco Discovery Protocol and LLDP).

Objective 2.3 sits in Network Access, which carries 20% of the CCNA exam. The questions below are original, written from the official objective title above, and each explanation cites the Cisco page it rests on.

Objective title verbatim from the official objectives. Cisco exam page ↗

A worked example

Shown solved, with the whole explanation open: this is what every question here carries.

2-3Network Access

A third-party switch is cabled to Gi1/0/9 and never appears in any neighbor listing, although the link is up.

SW1# show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater

Device ID    Local Intrfce   Holdtme   Capability  Platform  Port ID
SW2          Gig 1/0/1       147        S I        C9300-48  Gig 1/0/1

SW1# show lldp
% LLDP is not enabled

What has to be configured?

Enable LLDP globally, then permit transmit and receiveCorrect · your answerCorrect. The neutral protocol is off globally and per interface until both are set.
Raise the CDP holdtime so the entry is retained longerHoldtime governs how long a learned entry survives. It cannot produce an entry that was never learned.
Enable CDP version 2 advertisements on the interfaceVersion 2 advertisements are already the default state, and no version of the Cisco protocol reaches a device that does not run it.
Set Gi1/0/9 to trunk mode so neighbors are advertisedTrunking changes which VLANs a port carries. Discovery frames are exchanged on access ports too, so the port mode is not the obstacle.

Correct.

Checked against cisco.com, August 2026

Concept

Cisco's own discovery protocol only reports devices that speak it, so a switch from another vendor is invisible to it however healthy the link is. The vendor-neutral 802.1AB alternative covers that gap, and unlike the proprietary one it ships switched off at both the global and the interface level.

Why A

The neighbor listing finds the Catalyst peer and misses the other vendor's switch, which is the expected split. Turning on the neutral protocol takes two steps here because its defaults are off everywhere: one global command, then transmit and receive on the interface that faces the device.

Source

Step 3 lldp run Example: Device(config)# lldp run Enables LLDP globally on the device. Step 4 interface interface-id ... Step 5 lldp transmit Example: Device(config-if)# lldp transmit Enables the interface to send LLDP packets. Step 6 lldp receive Example: Device(config-if)# lldp receive Enables the interface to receive LLDP packets.

Cisco: Configuring LLDP, LLDP-MED, and Wired Location Service (Catalyst 9300, IOS XE 17.3.x), checked August 2026
#lldp#cdp#neighbor-discovery

Now you: objective 2.3 questions

No account needed. The explanation opens when you answer.

Sample question 1 of 2

2-3Network Access

SW4 was powered off two minutes ago and its peer still lists it.

SW1# show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater

Device ID    Local Intrfce   Holdtme   Capability  Platform  Port ID
SW4          Gig 1/0/2       41         S I        C9300-24  Gig 1/0/1
SW5          Gig 1/0/3       164        S I        C9300-24  Gig 1/0/1

Why is SW4 still listed?

Sample question 2 of 2

2-3Network Access

An access switch runs LLDP, but a core router two hops away never appears in its neighbor table. What information does LLDP actually provide?

That’s 2 of the full CCNA bank.

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Read the sources

These are the official pages the questions above cite. Reading them is studying the objective from the primary source, which is what the explanations point you toward anyway.

More objectives in Network Access