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Difficulty: MediumLayer 2 Discovery Protocols (CDP and LLDP)

A network administrator is deploying Link Layer Discovery Protocol (LLDP) across a multi-vendor switch infrastructure. Which two statements correctly describe the default operational characteristics and CLI configuration of LLDP on Cisco Catalyst switches compared to CDP? (Select TWO.)

  1. LLDP is globally disabled by default on Cisco Catalyst switches and requires the global configuration command `lldp run` to be enabled.Answer
  2. LLDP allows granular, independent control of message transmission and reception on specific interfaces using `lldp transmit` and `lldp receive` interface commands.Answer
  3. C
    LLDP operates with default timers of a 60-second advertisement frequency and a 180-second holdtime, matching the default timer values of CDP.
  4. D
    LLDP automatically resolves native VLAN mismatches across trunk links by dynamically renegotiating 802.1Q tagging attributes.

Answer

LLDP is globally disabled by default on Cisco Catalyst switches requiring `lldp run`, and LLDP provides independent control over transmit and receive states per interface using `lldp transmit` and `lldp receive`.
The correct choices accurately state that LLDP is disabled globally by default on Cisco Catalyst switches (requiring `lldp run` in global configuration mode) and that LLDP supports independent interface-level transmit and receive controls (`lldp transmit` / `lldp receive`).

Step-by-Step Solution

1
Analyze global protocol state defaults
Cisco Catalyst switches ship with CDP globally enabled by default (`cdp run`), whereas LLDP is globally disabled by default and requires `lldp run` to start discovery processes.
CDP is Cisco proprietary and enabled by default, while IEEE 802.1AB LLDP must be explicitly activated globally on Cisco Catalyst platforms.
2
Evaluate interface-level control capabilities
LLDP allows separate commands for sending (`lldp transmit`) and listening (`lldp receive`), providing granular directional control that CDP (`cdp enable`) does not offer.
LLDP's standard specification allows interfaces to act as receive-only, transmit-only, or bidirectional discovery nodes.
3
Verify protocol default timers
CDP uses a 60-second advertisement interval and a 180-second holdtime. LLDP on Cisco devices uses a 30-second advertisement interval and a 120-second holdtime.
Confusing LLDP default timers with CDP default timers is a common misconception when analyzing discovery protocol operational states.

Key Concept

CDP vs LLDP Operational Differences and CLI Configuration
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Topics

Layer 2 Discovery Protocols (CDP and LLDP)

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