What information should I collect in preparation for a networking Root Cause Analysis?

Issue

• What information should I collect in preparation for a network Root Cause Analysis?

• The right information is dependent on the circumstance that you receive, different logs may be relevant at the time of the incident.
  The following is a list of network related RCA (Root Cause Analysis)

• Network Flapping (network interface showing status failures in messages with up and down events)

• The Network card hung
• Network related errors seen in /var/log/messages
• Retransmission (loss of packets seen)
• Connection related Issues
  - Connection lost to source
  - Connection lost when connecting from source to destination