How to capture and analyze IPSEC traffic or why do I see un-encrypted packets going through an IPSEC tunnel

Solution Unverified - Updated -

Issue

  • While running Openswan VPN is it possible to troubleshoot VPN traffic that flows into the ipsec tunnel?
  • Apparently using tcpdump it's not possible to see the traffic going into the tunnel.
  • Is it somehow possible to trace traffic that goes into the tunnel or is rejected/dropped by the tunnel?

Environment

  • Red Hat Enterprise Linux
  • ipsec tunnel based on Openswan

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