How do I detect a duplicate IP address on my network?

Solution Verified - Updated -

Issue

  • How to check for a duplicate IP address in the network?
  • How do I detect a duplicate IP address on my network?
  • Error, some other host already uses address is printed when running service network restart or ifup.
  • SSH connections breaking then reporting a different key when reconnecting (and/or not accepting the correct password)
  • Systems intermittently connectable via IP on the same network subnet

Environment

  • Red Hat Enterprise Linux (all versions)
  • IP networking

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