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Sunday, August 12, 2012

Troubleshooting Cisco Switches

General Switching : troubleshooting 
  • Troubleshooting a switched network
    • get familiar with the network
    • absolutely have an accurate network diagram
    • work logically, from the bottom up (OSI)
  • Common Troubleshooting Issues
    • Port issues:
      • check cabling issues
      • verify speed and duplex auto negotiation
      • check that assigned vlan has not been deleted
    • Spanning Tree Issues
      • solve the immediate issue (disconnect redundant link)
      • ensure that all links are reflected on the network diagram
      • ensure that the root bridge selection is appropriate
      • make sure all switches are running RSTP
      • there is a 7 switch limit to STP
    • VLAN and trunking issues
      • watch for native vlan mismatch
      • hard code trunk ports to on
      • verify IP address assignments in a vlan
      • use ping and traceroute to diagnose routing issues
    • VTP Issues
      • verify trunks
      • verify vtp info: name, password, version, modes
      • last resort: delete flash:vlan.dat and reconfig

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