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Zorluk: ZorLayer 2 Discovery Protocols (CDP and LLDP)

A network engineer is configuring Layer 2 neighbor discovery on Cisco Catalyst switches and multi-vendor endpoints. Match each Layer 2 discovery protocol characteristic or CLI configuration element on the left with its corresponding operational parameter or behavior on the right.

  • Cisco Discovery Protocol (CDP) Default Timers60-second update transmission interval and 180-second holdtime
  • Link Layer Discovery Protocol (LLDP) Default Timers30-second update transmission interval and 120-second holdtime (holdtime multiplier of 4)
  • LLDP Interface Directional Control SyntaxGranular subcommands allowing outbound frame sending and inbound frame processing to be controlled independently per interface
  • LLDP-MED (ANSI/TIA-1057) Capability TargetExtends discovery to endpoint devices for voice VLAN assignment, location details, and dynamic Power over Ethernet (PoE) negotiation

Cevap

CDP Default Timers match with a 60-second update transmission interval and 180-second holdtime. LLDP Default Timers match with a 30-second update transmission interval and 120-second holdtime (holdtime multiplier of 4). LLDP Interface Directional Control Syntax matches with granular subcommands allowing outbound frame sending and inbound frame processing to be controlled independently per interface. LLDP-MED Capability Target matches with extending discovery to endpoint devices for voice VLAN assignment, location details, and dynamic Power over Ethernet (PoE) negotiation.
The correct mapping aligns CDP with its proprietary default timers (60s update / 180s holdtime), LLDP with IEEE 802.1AB default timers (30s update / 120s holdtime calculated via a multiplier of 4), interface-level LLDP directional control ('lldp transmit' and 'lldp receive'), and LLDP-MED with multi-vendor endpoint management features (voice VLAN provisioning and dynamic PoE allocation).

Adım Adım Çözüm

1
Evaluate the default transmission and holdtime values for CDP and standard LLDP.
CDP defaults to sending announcements every 60 seconds with a 180-second holdtime. IEEE 802.1AB LLDP defaults to sending frames every 30 seconds with a holdtime multiplier of 4 (giving a 120-second holdtime).
Identifying the exact timer specifications avoids confusing vendor-proprietary timer defaults with IEEE standard defaults.
2
Analyze interface configuration mechanisms for directional frame control.
CDP is toggled per interface with 'cdp enable'. LLDP provides independent control over transmission ('lldp transmit') and reception ('lldp receive') at the interface level.
Network security policies often mandate disabling advertisement transmissions on public-facing or untrusted access ports while still permitting inbound neighbor logging.
3
Identify protocol extensions for specialized media endpoints like IP phones.
LLDP-MED (ANSI/TIA-1057) builds upon IEEE 802.1AB by defining specific Type-Length-Value (TLV) headers for Voice VLAN configuration, physical location tracking, and granular power-via-MDI negotiation.
Multi-vendor VoIP deployments rely on LLDP-MED to achieve seamless endpoint provisioning on non-Cisco switches or cross-vendor telephony platforms.

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Layer 2 Discovery Protocols (CDP and LLDP Parameters and Configurations)
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Layer 2 Discovery Protocols (CDP and LLDP)

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