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Layer 2 Discovery Protocols (CDP and LLDP)

31 questions

All types31Multiple choice16Multiple select7Matching8
Question 1Question →

A network administrator is configuring and verifying Layer 2 discovery protocols across a enterprise topology consisting of Cisco and multi-vendor switches. Match each Cisco IOS command on the left with its corresponding operational scope and function on the right.

Click a left item, then click its matching right item

Items

cdp run
no cdp enable
lldp transmit
show lldp neighbors detail

Matches

Show answer & explanation

Answer

The correct matches pair 'cdp run' with 'Global configuration command that enables Cisco Discovery Protocol across all supported device interfaces.', 'no cdp enable' with 'Interface configuration command that disables Cisco Discovery Protocol on a specific interface.', 'lldp transmit' with 'Interface configuration command that selectively enables sending Link Layer Discovery Protocol packets out of an interface.', and 'show lldp neighbors detail' with 'Privileged EXEC mode command that displays expanded neighbor information, including management IP addresses and system capabilities.'
Each Cisco IOS command corresponds directly to a specific scope and function: 'cdp run' turns on CDP globally across the chassis, 'no cdp enable' disables CDP on an individual port, 'lldp transmit' enables outbound LLDP packet transmission on a specific port, and 'show lldp neighbors detail' provides detailed neighbor operational information.

Step-by-Step Solution

1
Identify the configuration scope (global vs. interface vs. EXEC mode) for each command.
'cdp run' is global configuration; 'no cdp enable' and 'lldp transmit' are interface configuration; 'show lldp neighbors detail' is EXEC mode verification.
Understanding mode syntax is critical for proper Layer 2 discovery protocol deployment.
2
Distinguish CDP single-state toggle from LLDP directional interface controls.
CDP uses 'cdp enable' / 'no cdp enable' per interface, whereas LLDP uses separate 'lldp transmit' and 'lldp receive' commands per interface.
LLDP provides granular directional transmission control that CDP does not.
3
Map each command to its precise definition.
Match left_1 to right_1, left_2 to right_2, left_3 to right_3, and left_4 to right_4.
Validates proper CLI syntax and operational scope for Cisco IOS discovery protocols.

Key Concept

CDP and LLDP CLI Syntax, Configuration Scopes, and Verification Commands
Question 2Question →

A network administrator is replacing legacy Cisco access switches with multi-vendor infrastructure. On a Cisco Catalyst switch (SW-Access1), the administrator attempts to selectively enable Link Layer Discovery Protocol (LLDP) on interface GigabitEthernet1/0/5 to discover an adjacent non-Cisco VoIP gateway while disabling Cisco Discovery Protocol (CDP) on that specific link.

The administrator enters interface configuration mode and attempts the following command sequence:

SW-Access1(config)# interface gigabitethernet1/0/5
SW-Access1(config-if)# no cdp enable
SW-Access1(config-if)# lldp enable

The switch returns an error: `% Invalid input detected at '^' marker` pointing to the `enable` keyword.

Which combination of commands must the administrator issue to globally activate LLDP and correctly enable both transmission and reception of LLDP packets on interface GigabitEthernet1/0/5?

Show answer & explanation

Answer: Execute 'lldp run' in global configuration mode, and execute both 'lldp transmit' and 'lldp receive' in interface configuration mode.

Answer

Execute 'lldp run' in global configuration mode, and execute both 'lldp transmit' and 'lldp receive' in interface configuration mode.
The correct answer specifies 'lldp run' in global configuration mode and both 'lldp transmit' and 'lldp receive' in interface configuration mode. In Cisco IOS, CDP and LLDP differ significantly in CLI command syntax and defaults. CDP is enabled globally by default and uses 'cdp enable' per interface. Conversely, LLDP is disabled globally by default (requiring 'lldp run') and controls interface communication via directional parameters ('lldp transmit' and 'lldp receive').

Step-by-Step Solution

1
Identify the global configuration command required to enable LLDP across the Cisco Catalyst switch.
Unlike CDP which is enabled globally by default ('cdp run'), LLDP is disabled globally by default and must be enabled using the global configuration command 'lldp run'.
Global activation of the LLDP process is a prerequisite before interface-level behavior can be configured.
2
Analyze interface-level configuration syntax differences between CDP and LLDP in Cisco IOS.
CDP uses a simple binary interface toggle command ('cdp enable' / 'no cdp enable'). LLDP does not use the 'enable' keyword at the interface level; instead, it provides directional control using 'lldp transmit' and 'lldp receive'.
Attempting to enter 'lldp enable' on a Cisco IOS interface causes an invalid input error because 'enable' is not a valid sub-command under 'lldp'.
3
Synthesize the required global and interface commands to achieve the administrator's goal.
Issue 'lldp run' globally, and under interface GigabitEthernet1/0/5 issue 'no cdp enable', 'lldp transmit', and 'lldp receive'.
This setup disables CDP on the specific interface while enabling bidirectional LLDP communication with adjacent multi-vendor devices.

Key Concept

Cisco IOS CLI Syntax and Directional Operational Differences Between CDP and LLDP
Question 3Question →

A network administrator executes the following command on switch SW-Core1 to verify direct physical connections:

SW-Core1# show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone

Device ID Local Intrfce Holdtme Capability Platform Port ID
SW-Access2 Gig 1/0/1 158 S I WS-C3850 Gig 1/0/24

Based on this output, which local physical interface on SW-Core1 is connected to the neighboring switch?

Show answer & explanation

Answer: GigabitEthernet 1/0/1

Answer

GigabitEthernet 1/0/1 is the local physical interface on SW-Core1 connected to the neighboring device.
The 'show cdp neighbors' command displays summary information about directly connected Cisco devices. The 'Local Intrfce' field specifies the local interface on the current device (SW-Core1) where the CDP frames are received, which is GigabitEthernet 1/0/1. The 'Port ID' field indicates the port on the neighboring device (GigabitEthernet 1/0/24).

Step-by-Step Solution

1
Examine the output headers of the 'show cdp neighbors' command
Identify that 'Local Intrfce' corresponds to the local device interface, while 'Port ID' corresponds to the remote neighbor interface.
CDP separates local interface information from peer interface information across distinct table columns.
2
Locate the entry under the 'Local Intrfce' column for SW-Access2
The column value displays 'Gig 1/0/1'.
This confirms that SW-Core1 receives CDP advertisements from SW-Access2 on its local interface GigabitEthernet 1/0/1.

Key Concept

CDP Neighbor Table Data Fields Interpretation
Estimated Time:1m 0s
Question 4Question →

Match each Layer 2 discovery protocol attribute or configuration parameter on the left to its corresponding protocol or timer specification on the right.

Click a left item, then click its matching right item

Items

Cisco proprietary protocol enabled globally by default on Cisco switch platforms
Vendor-neutral discovery protocol standardized under IEEE 802.1AB
Protocol default update frequency of 60 seconds with a holdtime of 180 seconds
Protocol default update frequency of 30 seconds with a holdtime of 120 seconds

Matches

Show answer & explanation

Answer

The Cisco proprietary protocol matches Cisco Discovery Protocol (CDP). The IEEE 802.1AB standard matches Link Layer Discovery Protocol (LLDP). The 60-second update and 180-second holdtime match CDP Default Timers. The 30-second update and 120-second holdtime match LLDP Default Timers.
Each left-side item correctly correlates to its designated discovery protocol origin, governing IEEE specification, or default timer values.

Step-by-Step Solution

1
Differentiate between proprietary and open standard Layer 2 discovery protocols.
Identify CDP as Cisco proprietary and LLDP as IEEE 802.1AB standard.
CDP operates exclusively on Cisco devices by default, whereas LLDP allows interoperability across heterogeneous vendor environments.
2
Compare default advertisement and holdtime timers for CDP and LLDP.
Map 60s update / 180s holdtime to CDP, and 30s update / 120s holdtime to LLDP.
CDP sends updates less frequently (60s) than LLDP (30s) under default Cisco IOS configurations.

Key Concept

Layer 2 Discovery Protocols (CDP vs LLDP standards, ownership, and default timers)
Question 5Question →

A network engineer is troubleshooting Layer 2 protocol operations between a Cisco Catalyst switch (SW-1) and an adjacent third-party switch (SW-2). The engineer executes the `show lldp neighbors detail` command on SW-1 and reviews the following output:

SW-1# show lldp neighbors detail
------------------------------------------------
Local Interface: Gi1/0/12
Chassis id: 0050.56a1.b2c3
Port id: Eth101/1/5
Port Description: Ethernet101/1/5
System Name: SW-2-AGG
System Description: Vendor-X Enterprise Operating System v8.4
Time remaining: 114 seconds
System Capabilities: B, R
Enabled Capabilities: B
Management Addresses:
IP: 192.168.40.254
Auto Negotiation - supported, enabled
Physical media capabilities:
1000baseT(FD)
VLAN Information:
Native VLAN: 10

Assuming SW-1 port GigabitEthernet1/0/12 is configured as an 802.1Q trunk using default native VLAN 1 and default LLDP timer settings, which diagnosis and remediation step accurately reflect this state?

Show answer & explanation

Answer: A native VLAN mismatch exists because the remote device advertises native VLAN 10 over IEEE 802.1AB TLVs while SW-1 uses native VLAN 1; the native VLAN settings must be synchronized on both switch ports to prevent traffic leakage.

Answer

A native VLAN mismatch exists because the remote device advertises native VLAN 10 over IEEE 802.1AB TLVs while SW-1 uses native VLAN 1; the native VLAN settings must be synchronized on both switch ports to prevent traffic leakage.
The detailed LLDP output explicitly indicates that the remote switch (SW-2-AGG) is sending LLDP Type-Length-Value (TLV) data showing its native VLAN as 10. Since SW-1 is configured with the default native VLAN 1 on its trunk port (Gi1/0/12), a native VLAN mismatch exists across the 802.1Q trunk. Aligning the native VLAN configurations on both connected switch interfaces fixes the mismatch.

Step-by-Step Solution

1
Analyze the local vs remote interface fields in the LLDP output.
Local Interface is GigabitEthernet1/0/12 (on SW-1). Port id/description is Eth101/1/5 (on remote neighbor SW-2-AGG).
Correctly identifying local versus remote identifiers prevents interface role misinterpretation.
2
Evaluate the protocol timers displayed in the output.
'Time remaining: 114 seconds' reflects LLDP's standard holdtime (default 120 seconds = 30s hello × 4 holdtime multiplier).
This confirms that LLDP discovery is operating normally and is not timing out or relying on CDP 180s timers.
3
Examine the Organizationally Specific VLAN TLV output.
The neighbor advertises Native VLAN: 10 via LLDP TLVs, whereas SW-1 uses default native VLAN 1 on trunk Gi1/0/12.
An unmanaged difference in native VLAN configuration across an 802.1Q trunk leads to VLAN hopping vulnerabilities, STP errors, and traffic leakage.

Key Concept

LLDP CLI Output Analysis and Native VLAN Mismatch Detection
Estimated Time:2m 0s
Question 6Question →

A network technician displays the active Layer 2 discovery parameters on a switch port using the `show cdp interface gigabitethernet 0/1` command and observes the following output:

text
GigabitEthernet0/1 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 60 seconds
Holdtime is 180 seconds

If the technician disables CDP on this interface and enables Link Layer Discovery Protocol (LLDP) globally and locally, which default update timer and holdtime timer values will LLDP use?

Show answer & explanation

Answer: Update timer of 30 seconds and holdtime timer of 120 seconds

Answer

Update timer of 30 seconds and holdtime timer of 120 seconds
The correct answer specifies an update timer of 30 seconds and a holdtime timer of 120 seconds. In Cisco IOS, LLDP transmits discovery advertisements every 30 seconds by default and retains neighbor information for 120 seconds (using a holdtime multiplier of 4).

Step-by-Step Solution

1
Identify the default timer parameters for Cisco Discovery Protocol (CDP)
CDP defaults to transmitting advertisement frames every 60 seconds with a holdtime value of 180 seconds.
This establishes the baseline shown in the CLI command output.
2
Recall default timer parameters for IEEE 802.1AB Link Layer Discovery Protocol (LLDP)
LLDP defaults to an update message interval of 30 seconds and a holdtime multiplier of 4 (30×4=12030 \times 4 = 120 seconds).
Standard IEEE LLDP specifications mandate shorter advertisement intervals and holdtimes than proprietary CDP.
3
Compare the option choices to select the accurate LLDP default timer values
The option specifying an update timer of 30 seconds and a holdtime timer of 120 seconds is correct.
It accurately reflects standard Cisco IOS default behavior when LLDP is enabled.

Key Concept

CDP vs LLDP Default Timers
Question 7Question →

Match each Layer 2 discovery protocol standard, default operational timer, or feature extension on the left with its correct specification on the right.

Click a left item, then click its matching right item

Items

IEEE 802.1AB
CDP Default Holdtime
LLDP Default Advertisement Timer
LLDP-MED

Matches

Show answer & explanation

Answer

IEEE 802.1AB matches the vendor-neutral open standard specification defining Link Layer Discovery Protocol. CDP Default Holdtime matches 180 seconds. LLDP Default Advertisement Timer matches 30 seconds. LLDP-MED matches the extension supporting inventory management, power-over-Ethernet (PoE) negotiation, and network policy discovery for IP endpoints.
Each pair correctly matches the protocol standard, operational timers, and functional extensions: IEEE 802.1AB defines open-standard LLDP, CDP uses a 180-second default holdtime (3x its 60-second update timer), LLDP sends frames every 30 seconds by default, and LLDP-MED adds organizationally specific Type-Length-Values (TLVs) for media endpoints such as IP phones.

Step-by-Step Solution

1
Identify protocol standard numbers
IEEE 802.1AB corresponds directly to the open standard protocol for LLDP.
CDP is Cisco-proprietary and has no IEEE standard number, whereas LLDP was standardized under IEEE 802.1AB.
2
Differentiate default timers between CDP and LLDP
CDP advertises every 60 seconds with a 180-second holdtime. LLDP advertises every 30 seconds with a 120-second holdtime (holdtime multiplier of 4).
Matching CDP holdtime yields 180 seconds and LLDP advertisement timer yields 30 seconds.
3
Identify media endpoint discovery extensions
LLDP-MED enhances standard LLDP specifically for VoIP phones and endpoint discovery capabilities including voice VLAN assignments and PoE capabilities.
This matches the endpoint management and policy discovery description.

Key Concept

Layer 2 Discovery Protocols (CDP and LLDP) operational specifications and standards
Question 8Question →

A network administrator is troubleshooting neighbor visibility on a Cisco Catalyst switch (SW-1) connected to a non-Cisco switch. The administrator executes the `show lldp entry Core-SW2` command on SW-1 and receives the following CLI output:

text
Local Interface: Gi1/0/24
Chassis id: 0014.f2ca.8800
Port id: Eth1/1
Port Description: Trunk-to-Core1
System Name: Core-SW2

System Description:
Cisco Nexus Operating System (NX-OS) Software, Version 9.3(5)

Time remaining: 92 seconds
System Capabilities: B, R
Enabled Capabilities: B, R

Management Addresses:
IP: 10.1.100.2

Auto Negotiation: supported, enabled
Physical media capabilities:
1000baseT(FD)

Media Attachment Unit type: 30
VLAN Advertised: 10, 20, 99
Port VLAN ID (PVID): 99

Based on this LLDP detailed output, which conclusion correctly interprets the neighbor properties and link configuration?

Show answer & explanation

Answer: The local switch interface receiving the LLDP frames is GigabitEthernet1/0/24, while the remote neighbor's egress port is Ethernet1/1 with a native VLAN (PVID) of 99.

Answer

The local switch interface receiving the LLDP frames is GigabitEthernet1/0/24, while the remote neighbor's egress port is Ethernet1/1 with a native VLAN (PVID) of 99.
In Cisco IOS LLDP detailed entries (`show lldp entry` or `show lldp neighbors detail`), 'Local Interface' indicates the interface on the local device where the frame arrived (Gi1/0/24). The 'Port id' field identifies the remote neighboring device's egress interface (Eth1/1). Furthermore, the 'Port VLAN ID (PVID)' field reflects the native VLAN advertised by the adjacent device for that link.

Step-by-Step Solution

1
Analyze the Local Interface and Port ID fields in the LLDP output
'Local Interface: Gi1/0/24' represents the local switch's port receiving the LLDP frame. 'Port id: Eth1/1' specifies the interface on the remote neighboring device (Core-SW2).
LLDP output explicitly distinguishes between the local port where traffic is received and the remote port ID advertised by the neighbor.
2
Examine the Port VLAN ID (PVID) TLV information
'Port VLAN ID (PVID): 99' is the native VLAN ID advertised by the neighbor device (Core-SW2) for its port Eth1/1.
IEEE 802.1AB LLDP includes Organizationally Specific TLVs that advertise port attributes of the remote sender, including its configured native VLAN (PVID).
3
Evaluate the remaining timer information
'Time remaining: 92 seconds' is the dynamic countdown timer before the cached entry expires, not the configured holdtime constant.
The default LLDP holdtime multiplier (4) with a default message frequency (30s) yields a default holdtime of 120s; 92 seconds is merely the current countdown state.

Key Concept

Interpretation of LLDP Detailed CLI Neighbor Data and IEEE 802.1AB TLVs
Estimated Time:2m 0s
Question 9Question →

A network administrator executes the `show cdp neighbors` command on a Cisco Catalyst switch to inspect connected devices and receives the following output:

Device ID Local Intrfce Holdtme Capability Platform Port ID
SW-ACCESS-02 Gig 0/1 162 R S I WS-C3560 Gig 0/24

Based on this command output, which interface on the local switch directly connects to neighboring switch SW-ACCESS-02?

Show answer & explanation

Answer: GigabitEthernet 0/1

Answer

The local switch interface connected to SW-ACCESS-02 is GigabitEthernet 0/1.
In the `show cdp neighbors` command output, the 'Local Intrfce' column specifies the physical interface on the current (local) switch where the CDP advertisement was received. For the entry corresponding to device SW-ACCESS-02, the 'Local Intrfce' is GigabitEthernet 0/1 (abbreviated as Gig 0/1).

Step-by-Step Solution

1
Examine the column headers of the `show cdp neighbors` output
Identify the columns for neighbor identity ('Device ID'), local port ('Local Intrfce'), remaining hold time ('Holdtme'), neighbor platform ('Platform'), and remote port ('Port ID').
Understanding the CLI output structure allows distinguishing local interface bindings from remote device port identifiers.
2
Locate the entry corresponding to Device ID 'SW-ACCESS-02'
Match 'SW-ACCESS-02' with its row entry.
The row contains parameters specifically sent by and associated with that neighboring device.
3
Read the value under the 'Local Intrfce' column for that row
The value is 'Gig 0/1', corresponding to local interface GigabitEthernet 0/1.
The 'Local Intrfce' field explicitly specifies the port on the local switch receiving the CDP advertisements from the neighbor.

Key Concept

CDP Neighbor Output Data Parsing (Local vs Remote Interface Identification)
Question 10Question →

A network administrator is troubleshooting neighbor discovery on a Cisco Catalyst switch connected to a multi-vendor IP phone on interface GigabitEthernet1/0/5. Global LLDP has already been enabled with the `lldp run` command. However, output from `show lldp neighbors` indicates that while the switch successfully processes incoming packets from the IP phone, the IP phone is not receiving any LLDP advertisements from the switch.

Which interface configuration command must be applied under interface GigabitEthernet1/0/5 to resolve this issue and allow the switch to send LLDP frames to the phone?

Show answer & explanation

Answer: lldp transmit

Answer

The command 'lldp transmit' must be configured under interface GigabitEthernet1/0/5 to allow outbound LLDP advertisements.
The correct answer specifies 'lldp transmit'. Unlike Cisco Discovery Protocol (CDP), which uses a single interface command ('cdp enable'), Link Layer Discovery Protocol (LLDP) provides granular directional control on interfaces. The 'lldp transmit' interface submode command explicitly instructs the Cisco switch port to generate and send outbound LLDP frames to adjacent devices.

Step-by-Step Solution

1
Identify the protocol and scope required
The target protocol is LLDP (IEEE 802.1AB) operating at the interface level on a Cisco Catalyst switch.
Global LLDP is active, but outbound transmission on GigabitEthernet1/0/5 is currently disabled or missing.
2
Differentiate CDP and LLDP interface command syntax
CDP uses 'cdp enable' on interfaces, whereas LLDP uses separate direction-specific submode commands: 'lldp transmit' and 'lldp receive'.
LLDP allows directional control over transmission and reception per port.
3
Select the correct directional interface submode command
Applying 'lldp transmit' enables outbound advertisement of local switch Type-Length-Value (TLV) attributes.
The issue specifically states that incoming packets are received but outbound packets are not being sent.

Key Concept

LLDP Interface Configuration Commands
Estimated Time:1m 0s
Question 11Question →

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

Click a left item, then click its matching right item

Items

IEEE 802.1AB
CDP Default Holdtime
LLDP-MED
lldp transmit

Matches

Show answer & explanation

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
Question 12Question →

A network engineer is integrating non-Cisco VoIP endpoints and access points into an existing Cisco Catalyst switch infrastructure. The engineer needs to ensure automated VLAN assignment and power negotiation function properly across the multi-vendor environment while maintaining Layer 2 discovery. Which two statements regarding the operation and configuration of CDP and LLDP in this scenario are correct?

Select all that apply

Show answer & explanation

Answer: LLDP-MED (Media Endpoint Discovery) is an IEEE 802.1AB extension that enables detailed power management, location identification, and automated voice VLAN policy discovery between network switches and IP endpoints.; CDP and LLDP operate as completely independent processes, allowing both protocols to run concurrently on the same interface without interfering with each other's neighbor tables.

Answer

The two correct statements state that LLDP-MED is an IEEE 802.1AB extension enabling automated endpoint discovery features like voice VLAN policy assignment and power management, and that CDP and LLDP operate independently as separate protocols on the same interface.
LLDP-MED enhances standard IEEE 802.1AB by defining specific Type-Length-Value (TLV) fields for voice VLAN policy, location, and PoE management when connecting third-party endpoints. Additionally, CDP and LLDP are completely decoupled protocol stacks within Cisco IOS, running concurrently without mutual interference.

Step-by-Step Solution

1
Evaluate the capabilities of LLDP-MED in multi-vendor endpoint deployments.
Identified that LLDP-MED (Media Endpoint Discovery) is designed to supply Voice VLAN network policies, location info, and PoE details to multi-vendor devices.
Standard LLDP provides basic device discovery, whereas LLDP-MED extends IEEE 802.1AB for media endpoints such as IP phones.
2
Analyze protocol independence between CDP and LLDP.
Confirmed that Cisco IOS handles CDP (Cisco proprietary) and LLDP (IEEE standard) as separate internal processes.
Both protocols can simultaneously build their respective neighbor tables ('show cdp neighbors' and 'show lldp neighbors') on a shared interface.
3
Inspect interface command behavior for LLDP transmission and reception.
Disproved the claim that disabling transmit disables receive.
In Cisco IOS, 'lldp transmit' and 'lldp receive' are distinct granular interface commands.
4
Evaluate CDP framing standards.
Disproved the claim that CDP changes to IEEE 802.1AB.
CDP remains Cisco-proprietary regardless of connected neighbor devices.

Key Concept

CDP and LLDP Protocol Differences and Multi-Vendor Operations
Question 13Question →

Network administrators use Layer 2 discovery protocols to discover adjacent network hardware and verify topology details. Match each Layer 2 discovery protocol attribute on the left with its corresponding protocol characteristic or default value on the right.

Click a left item, then click its matching right item

Items

IEEE 802.1AB
Cisco Proprietary Discovery Protocol
Default CDP Holdtime
Default LLDP Holdtime

Matches

Show answer & explanation

Answer

IEEE 802.1AB matches Open vendor-neutral standard for Link Layer Discovery Protocol (LLDP); Cisco Proprietary Discovery Protocol matches Cisco Discovery Protocol (CDP); Default CDP Holdtime matches 180 seconds; Default LLDP Holdtime matches 120 seconds.
IEEE 802.1AB is the formal standard specification for LLDP. CDP is Cisco's proprietary discovery protocol. CDP defaults to an update timer of 60 seconds and a holdtime of 180 seconds, while LLDP defaults to a transmit timer of 30 seconds and a holdtime of 120 seconds.

Step-by-Step Solution

1
Identify the standard governing LLDP.
LLDP is defined under IEEE 802.1AB.
IEEE 802.1AB provides an open standard for neighbor discovery across multi-vendor equipment.
2
Identify the ownership model of CDP.
CDP is Cisco proprietary.
CDP was created by Cisco to allow Cisco switches, routers, and devices to discover each other.
3
Calculate or recall the default CDP holdtime.
The CDP holdtime defaults to 180 seconds.
CDP transmits messages every 60 seconds, and the default holdtime is set to 3 update intervals (180 seconds).
4
Calculate or recall the default LLDP holdtime.
The LLDP holdtime defaults to 120 seconds.
LLDP uses a default transmit timer of 30 seconds with a default holdtime multiplier of 4, producing a 120-second holdtime.

Key Concept

Distinguishing characteristics, standards, and default timers of CDP and LLDP.
Question 14Question →

An engineer is evaluating Layer 2 discovery protocol operations on a Cisco Catalyst switch connected to multi-vendor infrastructure. The switch is running the following active configuration:

text lldp run ! interface GigabitEthernet1/0/12 description Link to Non-Cisco Switch no cdp enable lldp transmit lldp receive ! interface GigabitEthernet1/0/24 description Link to VoIP Phone cdp enable no lldp transmit

During a network audit, the engineer issues the command `show lldp neighbors detail` and receives the following partial CLI output:

text ------------------------------------------------ Local Interface: Gi1/0/12 Chassis id: 0021.a012.3456 Port id: Eth1/1 Port Description: Ethernet1/1 System Name: SW-CORE-NEXUS System Description: Cisco Nexus Operating System (NX-OS) Software Time remaining: 105 seconds System Capabilities: Bridge, Router Enabled Capabilities: Bridge Management Addresses: IP: 10.1.100.2 Auto Negotiation: supported, enabled Physical media capabilities: 1000baseT(FD) Media Attachment Unit Type: 30 VLAN ID: 10

Which two conclusions accurately describe the protocol behavior and neighbor state for this switch based on the configuration and command output?

Select all that apply

Show answer & explanation

Answer: The local interface GigabitEthernet1/0/12 is successfully processing IEEE 802.1AB Type-Length-Value (TLV) data frames from the remote neighbor SW-CORE-NEXUS.; Interface GigabitEthernet1/0/24 will fail to transmit LLDP Data Units (LLDPDUs) to the connected VoIP phone, but it will continue sending CDP advertisements.

Answer

The local interface GigabitEthernet1/0/12 is processing IEEE 802.1AB Type-Length-Value (TLV) frames, and interface GigabitEthernet1/0/24 will refrain from transmitting outbound LLDP frames while retaining active CDP transmission.
LLDP relies on IEEE 802.1AB standard TLVs to exchange information between multi-vendor devices, which is demonstrated by the detailed attributes shown for SW-CORE-NEXUS on GigabitEthernet1/0/12. Furthermore, interface GigabitEthernet1/0/24 explicitly disables LLDP transmissions via 'no lldp transmit' while keeping CDP active via 'cdp enable'.

Step-by-Step Solution

1
Analyze interface GigabitEthernet1/0/12 configuration and protocol standard.
Interface Gi1/0/12 has CDP disabled and LLDP enabled ('lldp transmit' and 'lldp receive'). LLDP operates under IEEE 802.1AB using TLVs.
Verify standard protocol characteristics for LLDP neighbor discovery.
2
Evaluate interface GigabitEthernet1/0/24 interface commands.
'no lldp transmit' suppresses outgoing LLDP messages on Gi1/0/24, while 'cdp enable' maintains active CDP outbound frames.
Determine granular protocol control per interface.
3
Compare default CDP vs. LLDP holdtime timers against the CLI output.
CDP default holdtime is 180 seconds, while LLDP default holdtime is 120 seconds. Output shows 'Time remaining: 105 seconds', confirming a 120-second starting value for LLDP.
Differentiate default timer parameters between CDP and LLDP.

Key Concept

Layer 2 Discovery Protocol (CDP and LLDP) Operation, IEEE 802.1AB TLV Structure, and Per-Interface Control
Question 15Question →

A network administrator executes the following command on switch SW-1 to troubleshoot connectivity to an adjacent network device:

text
SW-1# show lldp neighbors detail
------------------------------------------------
Local Intf: Gi0/1
Chassis id: 0014.f25a.a100
Port id: GigabitEthernet1/0/24
Port Description: Trunk Link to SW-1
System Name: SW-2
System Description: Cisco IOS Software, C3750E Software (C3750E-UNIVERSALK9-M)
Time remaining: 98 seconds
System Capabilities: B, R
Enabled Capabilities: B
Management Addresses:
IP: 10.1.10.2
Auto Negotiation - supported, enabled
Physical media capabilities:
1000baseT(FD)
Media Attachment Unit type: 30
VLAN ID: 20

Based on the output provided, which conclusion accurately describes the neighbor relationship and port configuration?

Show answer & explanation

Answer: The adjacent switch SW-2 is connected via its interface GigabitEthernet1/0/24 to SW-1's local interface GigabitEthernet0/1, operating with a port VLAN ID of 20 and management address 10.1.10.2.

Answer

The adjacent switch SW-2 is connected via its interface GigabitEthernet1/0/24 to SW-1's local interface GigabitEthernet0/1, operating with a port VLAN ID of 20 and management address 10.1.10.2.
The output of 'show lldp neighbors detail' shows that local interface Gi0/1 on SW-1 is connected to remote port GigabitEthernet1/0/24 on system SW-2. It also displays SW-2's management IP (10.1.10.2), system capabilities, and the advertised Port VLAN ID of 20.

Step-by-Step Solution

1
Identify local vs. remote interface designations in the LLDP CLI output.
'Local Intf: Gi0/1' is the local interface on SW-1. 'Port id: GigabitEthernet1/0/24' represents the interface on the remote neighbor (SW-2).
Layer 2 discovery outputs distinguish between local ports where traffic is received and remote port IDs advertised by neighbors.
2
Analyze System Name, System Capabilities, and Management Addresses.
System Name is SW-2, Management IP is 10.1.10.2, and Enabled Capabilities is 'B' (Bridge/Switch).
Capability code 'B' stands for Bridge/Switch, proving the active role of the device is Layer 2 switching.
3
Evaluate the IEEE 802.1 TLV Port VLAN ID information.
'VLAN ID: 20' reflects the advertised Port VLAN ID (PVID) associated with the link.
LLDP advertises PVID through Organizationally Specific TLVs, allowing operators to verify VLAN settings on connected links.

Key Concept

Interpretation of IEEE 802.1AB LLDP detailed neighbor table outputs and TLV fields.
Estimated Time:2m 0s
Question 16Question →

A network engineer is configuring network topology discovery across a multi-vendor environment containing both Cisco and non-Cisco switches. Which IEEE standard defines the open, vendor-neutral Layer 2 discovery protocol used to identify neighboring devices?

Show answer & explanation

Answer: IEEE 802.1AB

Answer

IEEE 802.1AB is the IEEE standard that defines Link Layer Discovery Protocol (LLDP).
The IEEE 802.1AB standard formally defines Link Layer Discovery Protocol (LLDP). LLDP allows network devices to advertise identity, capabilities, and neighbor information across heterogeneous multi-vendor networks.

Step-by-Step Solution

1
Identify the protocol requirements from the scenario
The scenario calls for an open, vendor-neutral Layer 2 discovery protocol usable across multi-vendor equipment.
Cisco Discovery Protocol (CDP) is Cisco-proprietary, whereas Link Layer Discovery Protocol (LLDP) is open-standard.
2
Map LLDP to its governing IEEE standard specification
LLDP is standardized under IEEE 802.1AB.
IEEE 802.1AB specifies the Type-Length-Value (TLV) frame format and operational procedures for LLDP.

Key Concept

Link Layer Discovery Protocol (LLDP) IEEE standard identification
Question 17Question →

A network engineer needs to implement an open standard, vendor-neutral Layer 2 neighbor discovery protocol across a mixed enterprise network containing both Cisco and non-Cisco devices. Which protocol defined under IEEE 802.1AB meets this requirement?

Show answer & explanation

Answer: Link Layer Discovery Protocol (LLDP)

Answer

Link Layer Discovery Protocol (LLDP) is the IEEE 802.1AB standard protocol used for Layer 2 discovery in multi-vendor network environments.
Link Layer Discovery Protocol (LLDP) is defined by IEEE 802.1AB. It provides vendor-neutral Layer 2 neighbor discovery functionality, making it ideal for heterogeneous network environments with devices from multiple vendors.

Step-by-Step Solution

1
Identify the protocol requirements from the scenario.
The scenario specifies an open-standard, vendor-neutral Layer 2 discovery protocol governed by IEEE 802.1AB.
Multivendor environments cannot rely on proprietary protocols like CDP across non-Cisco switches.
2
Evaluate candidate protocols against IEEE standards.
LLDP is explicitly defined under the IEEE 802.1AB standard for network device discovery.
LLDP allows heterogeneous network devices to advertise capabilities, management IP, and interface details across vendor boundaries.

Key Concept

Layer 2 Discovery Protocols: CDP vs. LLDP Standards
Question 18Question →

A network technician is configuring Layer 2 neighbor discovery protocols on a Cisco Catalyst switch connected to non-Cisco IP phones and third-party switches. Which two statements regarding the default operations and characteristics of CDP and LLDP are accurate?

Select all that apply

Show answer & explanation

Answer: LLDP is an open-standard protocol defined under IEEE 802.1AB, whereas CDP is a Cisco-proprietary protocol.; CDP is enabled globally by default on Cisco IOS switches, while LLDP typically requires global enablement using the 'lldp run' command.

Answer

The two correct statements are that LLDP is an IEEE 802.1AB open standard while CDP is Cisco-proprietary, and that CDP is enabled by default on Cisco IOS switches while LLDP must be globally enabled using the 'lldp run' command.
LLDP is defined by IEEE 802.1AB as an open standard protocol, making it suitable for environments with equipment from multiple vendors, whereas CDP is a Cisco-proprietary protocol. Furthermore, Cisco switches default to having CDP enabled out-of-the-box, while LLDP must be globally enabled using the global configuration command 'lldp run'.

Step-by-Step Solution

1
Analyze standard compliance for Layer 2 discovery protocols.
LLDP is standardized under IEEE 802.1AB for multi-vendor interoperability, whereas CDP is proprietary to Cisco.
Understanding standard vs. proprietary protocol behavior is fundamental for multi-vendor network integration.
2
Evaluate default operating states on Cisco switches.
CDP is active globally out of the box on Cisco IOS, while LLDP requires explicit global activation via 'lldp run'.
Knowing default service states prevents assumptions about neighbor discovery availability.

Key Concept

Layer 2 Discovery Protocol Differences (CDP vs LLDP)
Question 19Question →

Network administrators must understand the key attributes, IEEE standards, and default operational parameters of Layer 2 discovery protocols when configuring enterprise switches. Match each Layer 2 discovery protocol characteristic on the left with its corresponding protocol specification or value on the right.

Click a left item, then click its matching right item

Items

IEEE 802.1AB
CDP Default Advertisement Interval
LLDP Default Holdtime
Cisco Discovery Protocol (CDP)

Matches

Show answer & explanation

Answer

IEEE 802.1AB matches the open IEEE standard defining LLDP; CDP Default Advertisement Interval matches 60 seconds; LLDP Default Holdtime matches 120 seconds; Cisco Discovery Protocol (CDP) matches the Cisco-proprietary Layer 2 discovery protocol enabled by default on Cisco Catalyst switches.
Each item accurately corresponds to its defining standard, default timer, or vendor status. IEEE 802.1AB specifies LLDP; CDP advertises every 60 seconds; LLDP retains neighbor entries for a default holdtime of 120 seconds (30s x 4); and CDP is a Cisco-proprietary protocol enabled out of the box.

Step-by-Step Solution

1
Identify the standard specification for LLDP
IEEE 802.1AB defines vendor-neutral LLDP
Standardization allows multi-vendor interoperability for discovery protocols.
2
Determine default CDP update interval
CDP transmits periodic updates every 60 seconds by default
Cisco IOS uses 60 seconds for update packets and 180 seconds for holdtime.
3
Calculate default LLDP holdtime value
LLDP transmit timer (30s) multiplied by holdtime multiplier (4) equals 120 seconds
LLDP calculates holdtime dynamically based on transmit frequency and multiplier.
4
Identify proprietary characteristics of CDP
CDP is Cisco-proprietary and active by default on Cisco hardware
Unlike LLDP, CDP does not require global enablement on standard Cisco switch platforms.

Key Concept

Layer 2 Discovery Protocols (CDP and LLDP) Timers and Standards
Estimated Time:1m 0s
Question 20Question →

A network administrator is deploying non-Cisco VoIP IP phones connected to a Cisco Catalyst switch. While Cisco Discovery Protocol (CDP) is enabled by default, the non-Cisco devices require Link Layer Discovery Protocol (LLDP) to receive VLAN assignments and power settings. Which command must the administrator execute in global configuration mode to enable LLDP globally across the switch?

Show answer & explanation

Answer: lldp run

Answer

The command `lldp run` entered in global configuration mode enables LLDP globally across the Cisco switch.
The command `lldp run` is executed in global configuration mode to start the LLDP service switch-wide on Cisco devices. Once enabled globally, individual interfaces will transmit and receive LLDP advertisements.

Step-by-Step Solution

1
Identify the protocol requirement
LLDP (IEEE 802.1AB) is required for interoperability with non-Cisco devices.
CDP is Cisco-proprietary, whereas LLDP is an open standard supported across multi-vendor equipment.
2
Determine the global CLI configuration syntax for LLDP
The command to enable LLDP globally on Cisco IOS is `lldp run`.
In Cisco IOS/IOS-XE, global protocol enablement for LLDP follows the syntax `lldp run` (similar to `ip routing` or `cdp run`).

Key Concept

Global activation of LLDP on Cisco Catalyst switches
Estimated Time:45s
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Layer 2 Discovery Protocols (CDP and LLDP) Practice Questions — Cisco CCNA | Examkin