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Cisco EtherChannel Troubleshooting
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Cisco EtherChannel Troubleshooting

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@TopnotchPhosphorus

Questions and Answers

What is the correct PAgP mode to configure when correcting an EtherChannel misconfiguration?

  • Auto
  • On
  • Passive
  • Desirable (correct)

    • Why is the order of EtherChannel-related commands significant?

  • To increase the EtherChannel speed
  • To prevent STP errors which may block ports (correct)
  • To enforce security protocols
  • To ensure efficient bandwidth usage

    • What command can be used to verify that an EtherChannel is operational?

  • show etherchannel configuration
  • show interface statistics
  • show etherchannel summary (correct)
  • show port-channel status

    • Which incorrect action could lead to STP errors during EtherChannel configuration?

    <p>Directly modifying the channel-group command</p> Signup and view all the answers

    What must EtherChannel and STP do in relation to each other?

    <p>Interoperate correctly</p> Signup and view all the answers

    What might happen if the configuration changes are made incorrectly for EtherChannel?

    <p>Ports might enter blocking or errdisabled states</p> Signup and view all the answers

    What should be done after changing the PAgP mode to desirable?

    <p>Verify through 'show etherchannel summary'</p> Signup and view all the answers

    What is a common mistake when configuring an EtherChannel?

    <p>Not using the correct PAgP mode</p> Signup and view all the answers

    What is the primary purpose of EtherChannel?

    <p>To increase bandwidth by combining multiple links.</p> Signup and view all the answers

    Which command is used to verify EtherChannel configuration?

    <p>show etherchannel summary</p> Signup and view all the answers

    What mode does PAgP use to negotiate link aggregation when it actively seeks to form a channel?

    <p>PAgP desirable</p> Signup and view all the answers

    How does LACP ensure interoperability with devices that do not support EtherChannel?

    <p>By using passive mode to wait for a channel initiation.</p> Signup and view all the answers

    Which command would you use if you want to see the status of a specific EtherChannel port?

    <p>show interfaces port-channel</p> Signup and view all the answers

    Which command is NOT used to troubleshoot EtherChannel configurations?

    <p>show vlan brief</p> Signup and view all the answers

    What does the command 'channel-group X mode passive' accomplish in LACP?

    <p>It waits for the partner to initiate connection.</p> Signup and view all the answers

    Which statement is true about PAgP modes?

    <p>PAgP auto does not initiate but responds to negotiation.</p> Signup and view all the answers

    In the context of link aggregation protocols, what does LACP stand for?

    <p>Link Aggregation Control Protocol</p> Signup and view all the answers

    What is the primary difference between PAgP and LACP?

    <p>PAgP only works on Cisco equipment, while LACP is vendor-agnostic.</p> Signup and view all the answers

    Which command can be used to verify an EtherChannel configuration?

    <p>show interfaces port-channel</p> Signup and view all the answers

    Which condition would prevent assigned ports from forming an EtherChannel?

    <p>Different native VLANs</p> Signup and view all the answers

    What must be compatible for PAgP to work correctly in an EtherChannel?

    <p>Allowed VLAN ranges on both ends</p> Signup and view all the answers

    What is a common issue when configuring EtherChannel if trunking is inconsistently applied?

    <p>Inconsistent trunking configurations on ports</p> Signup and view all the answers

    Which of the following PAgP modes must be set consistently between ports for successful negotiation?

    <p>Desirable and auto</p> Signup and view all the answers

    What command is used to display the general status of the port channel interface?

    <p>show interfaces port-channel</p> Signup and view all the answers

    Which command would you use to verify multiple port channels in a single command?

    <p>show etherchannel summary</p> Signup and view all the answers

    When configuring EtherChannel, which PAgP mode ensures passive participation in port aggregation?

    <p>Auto</p> Signup and view all the answers

    Which command provides specific information about a particular port channel interface?

    <p>show interfaces port-channel <number></p> Signup and view all the answers

    What is a primary benefit of configuring a redundant EtherChannel link?

    <p>Improved link reliability</p> Signup and view all the answers

    Which PAgP mode actively initiates the creation of an EtherChannel?

    <p>Desirable</p> Signup and view all the answers

    What becomes the default spanning tree behavior when using EtherChannel?

    <p>Single logical link representation</p> Signup and view all the answers

    Which common troubleshooting step can help identify issues with an EtherChannel configuration?

    <p>Check interface status</p> Signup and view all the answers

    If an EtherChannel is not functioning, which command is least likely to be useful in verification?

    <p>show run</p> Signup and view all the answers

    What information does the command 'show etherchannel summary' provide?

    <p>A line of information per port channel</p> Signup and view all the answers

    What does the output of the show etherchannel summary command indicate when the EtherChannel is down?

    <p>The EtherChannel is down.</p> Signup and view all the answers

    Which command should be used to view the detailed configuration of a port-channel interface?

    <p>show run | begin interface port-channel</p> Signup and view all the answers

    Incompatible configured PAgP modes on switches S1 and S2 typically lead to what outcome for EtherChannel?

    <p>EtherChannel is down.</p> Signup and view all the answers

    What is a potential cause for an EtherChannel connection to be non-operational?

    <p>Mismatched VLAN configurations on the switches.</p> Signup and view all the answers

    When troubleshooting an EtherChannel that is down, which of the following is a first step?

    <p>Review the EtherChannel summary.</p> Signup and view all the answers

    What can be inferred if the EtherChannel remains down despite correct configurations on S1?

    <p>Both switches are likely misconfigured.</p> Signup and view all the answers

    Which PAgP mode must be set identically on both switches for the EtherChannel to form?

    <p>Auto</p> Signup and view all the answers

    If an EtherChannel is misconfigured, what is the default mode of operation that might cause downtimes?

    <p>Switch port mode access</p> Signup and view all the answers

    What happens when switches have different EtherChannel load balancing settings?

    <p>Inconsistent traffic distribution occurs.</p> Signup and view all the answers

    What is a likely troubleshooting step if the show etherchannel summary indicates 'down' due to PAgP incompatibility?

    <p>Change both PAgP modes to 'Desirable'.</p> Signup and view all the answers

    Study Notes

    EtherChannel Troubleshooting Steps

    • Correcting misconfigurations involves changing PAgP mode to desirable to ensure interoperability with STP.
    • Entering EtherChannel commands in a specific order is crucial to avoid STP errors that can cause ports to enter a blocking or errdisabled state.
    • After correcting the configuration, use the show etherchannel summary command to verify that the EtherChannel is now operational.

    EtherChannel Configuration in Packet Tracer

    • Configure basic switch settings as part of EtherChannel setup.
    • Use Cisco PAgP for configuring a standard EtherChannel.
    • Implement 802.3ad for advanced EtherChannel configurations.
    • Ensure creation of redundant EtherChannel links for enhanced reliability.

    Verification Commands for EtherChannel

    • Utilize show interfaces port-channel to check the status of the port channel interface.
    • The show etherchannel summary command provides a concise summary for each port channel.
    • For detailed information on specific port channels, use show etherchannel port-channel.

    Key Terminology and Commands

    • Link Aggregation: Combining multiple physical links into a single logical link.
    • EtherChannel: A technology that allows bundling several Ethernet links.
    • Port Aggregation Protocol (PAgP): A Cisco proprietary protocol for EtherChannel.
    • Link Aggregation Control Protocol (LACP): An IEEE standard for link aggregation.
    • Important commands include:
      • channel-group X mode [ desirable | auto | active | passive ]
      • interface port-channel X
      • show interfaces etherchannel

    Common EtherChannel Issues

    • Failure to form EtherChannel due to:
      • Ports configured with different VLANs or trunk settings.
      • Inconsistent native VLANs across ports.
      • Mismatched trunk configuration among group ports.
      • Non-compatible dynamic negotiation settings for PAgP and LACP.

    Troubleshooting Example

    • If the EtherChannel is down, check the output of show etherchannel summary.
    • Inspect the configuration details with show run | begin interface port-channel to identify incompatible PAgP modes between connected switches.

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    Description

    Test your skills in verifying and troubleshooting EtherChannel configurations in Cisco networks. This quiz covers essential concepts and scenarios that network engineers face when dealing with EtherChannel issues. Perfect for reinforcing your knowledge and practical skills.

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