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Slowdown on Cisco Switch

Discussion in 'Routing & Switching' started by Methodman85, Feb 23, 2009.

  1. Methodman85

    Methodman85 Byte Poster

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    Hello Everyone,

    I'm a total noob with switches. A remote location is experience a local slowdown on systems connected to a Cisco 3500 series switch.
    The admin there suspects that a nic on one of the systems might be defective and chatty therefore causing the slowdown.
    Is there a command for the switch that would show the traffic accross each port to help narrow down the culpret?
    Or is there a better way to find a chatty NIC on the network?
    Microsoft's Network monitor perhaps?
     
    Certifications: MCTS, MCSE, MCSA:M, CCNA, MCDST, N+
    WIP: 70-680
  2. BosonMichael
    Highly Decorated Member Award

    BosonMichael Yottabyte Poster

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    Protocol analyzer.
     
    Certifications: CISSP, MCSE+I, MCSE: Security, MCSE: Messaging, MCDST, MCDBA, MCTS, OCP, CCNP, CCDP, CCNA Security, CCNA Voice, CNE, SCSA, Security+, Linux+, Server+, Network+, A+
    WIP: Just about everything!
  3. Spice_Weasel

    Spice_Weasel Kilobyte Poster

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    As BM said, a protocol analyzer will provide a huge amount of info, although experience is needed to make effective use of the output.

    Some quick switch commands to check include:

    show int <-- check for various errors, a quick filter would be sh int | inc Eth|error

    show proc cpu hist <-- check for excessive cpu usage

    show ip traff <-- look for drops and errors

    And also check the switch log/syslog/snmp for any info.

    Again, experience is key in understanding what the outputs indicate.

    Spice_Weasel
     
    Certifications: CCNA, CCNP, CCIP, JNCIA-ER, JNCIS-ER,MCP
    WIP: CCIE
  4. Methodman85

    Methodman85 Byte Poster

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    Thanks Guys.
    I used Microsoft's network monitor to look for excessive broadcasts. But found nothing major. I'm not totally convicnced it's a switch issue.
    I will give those commands a try. Thanks!
    I love how network stuff happens on day 1 of my IT Managers (Net Admin) extended leave!
     
    Certifications: MCTS, MCSE, MCSA:M, CCNA, MCDST, N+
    WIP: 70-680
  5. Methodman85

    Methodman85 Byte Poster

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    How chatty is chatty? I'm showing 3 systems with over 300 broadcasts in about 5 minutes.
    Is that pretty normal?
     
    Certifications: MCTS, MCSE, MCSA:M, CCNA, MCDST, N+
    WIP: 70-680
  6. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    Another possibility is the auto-negotiation failing. Particularly half/full duplex when talking to non-Cisco gear. This has bitten me many times.

    The usual fix is to nail it at both ends to the correct duplex setting.

    Harry.
     
    Certifications: ECDL A+ Network+ i-Net+
    WIP: Server+
  7. Sparky
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    Sparky Zettabyte Poster Moderator

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    Yup, seen this a few times myself. Ended up configuring the port manually rather than auto-negotiate.
     
    Certifications: MSc MCSE MCSA:M MCSA:S MCITP:EA MCTS(x5) Security+ Network+ A+
    WIP: Exchange 2007\2010
  8. snkeeyes

    snkeeyes New Member

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    I would think you could use IP accounting as well to see which ip is talking.
     

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