Link flap & err-disabled problem in CISO IOS


Link flap & err-disabled problem in CISO IOS

Link Flap Problem  :- 

  • Link flap means that the interface continually goes up and down.
  • The interface is put into the err disabled state if it flaps more than five times in 10 seconds.
  • The common cause of link flap is a Layer 1 issue such as a bad cable, duplex mismatch, or bad Gigabit Interface Converter (GBIC) card.
  • Look at the console messages or the messages that were sent to the syslog server that state the reason for the port shutdown.

err-disabled problem :- 

There are various reasons for the interface to go into err disable. The reason can be:

  • Duplex mismatch
  • Port channel miss-configuration
  • BPDU guard violation
  • Unidirectional Link Detection (UDLD) condition
  • Late-collision detection
  • Link-flap detection
  • Security violation
  • Port Aggregation Protocol (PAgP) flap
  • Layer 2 Tunneling Protocol (L2TP) guard
  • DHCP snooping rate-limit
  • Incorrect GBIC / Small Form-Factor Plug-gable (SFP) module or cable
  • Address Resolution Protocol (ARP) inspection
  • Inline power


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