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Difficulty: MediumLayer 2 Discovery Protocols (CDP and LLDP)

Match each Layer 2 discovery protocol characteristic or configuration parameter on the left with its correct operational description or standard on the right.

  • IEEE 802.1ABVendor-neutral open standard specification for Layer 2 neighbor discovery
  • CDP Default Holdtime180 seconds allocated before a Cisco device purges an inactive neighbor entry
  • LLDP-MEDExtension standard providing advanced endpoint attributes such as VoIP network policy and location
  • lldp transmitInterface-level command used to enable sending outgoing discovery frames on a specific port

Answer

IEEE 802.1AB matches the vendor-neutral open standard specification for Layer 2 discovery. CDP Default Holdtime matches 180 seconds before purging a neighbor entry. LLDP-MED matches the extension providing endpoint attributes such as VoIP policy. lldp transmit matches the interface-level command to enable sending outgoing discovery frames.
Each match correctly aligns the discovery protocol attribute, standards body designation, timer setting, or interface command syntax to its operational definition in Cisco IOS networks.

Step-by-Step Solution

1
Identify the standard associated with LLDP
IEEE 802.1AB defines the open-standard LLDP protocol across heterogenous network devices.
CDP is Cisco proprietary, whereas LLDP was developed under IEEE 802.1AB.
2
Recall CDP default timer values
CDP sends messages every 60 seconds and retains neighbor information for a holdtime of 180 seconds.
Knowing default timers is crucial for troubleshooting layer 2 neighbor relationships in Cisco networks.
3
Differentiate LLDP base protocol from LLDP-MED extensions
LLDP-MED extends base LLDP capability to advertise endpoint information like voice VLAN IDs, call control details, and PoE parameters.
LLDP-MED operates specifically between network infrastructure devices and media endpoints.
4
Analyze interface syntax for directional LLDP control
'lldp transmit' and 'lldp receive' control outgoing and incoming frames per interface.
Unlike CDP which is enabled bidirectionally when turned on, LLDP allows fine-grained directional enabling per interface.

Key Concept

Layer 2 Discovery Protocol Capabilities, Standards, and CLI Syntax
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Topics

Layer 2 Discovery Protocols (CDP and LLDP)

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