Why do I see "An illegal loopback occurred on adapter (ethX) Check the configuration to verify that all Adapters are connected to 802.3ad compliant switch ports" messages for bond devices configured in mode 4 in RHEL?

Solution Verified - Updated -

Issue

  • Following messages are frequently getting logged in the message logs:
bonding: bondX: An illegal loopback occurred on adapter (ethX). Check the configuration to verify that all Adapters are connected to 802.3ad compliant switch ports  

bonding: bondX: An illegal loopback occurred on adapter (ethX). Check the configuration to verify that all Adapters are connected to 802.3ad compliant switch ports
  • The bond device is configured in mode 4 (802.3ad) bonding. The host interfaces are split between two cisco Nexus switches configured in same vPC.
  • the slave interfaces seems to be up and unaffected by these messages.
  • Why are such messages seen? How to rectify them?

Environment

  • Red Hat Enterprise Linux(RHEL) 5+
  • Red Hat Enterprise Linux(RHEL) 6+
  • Red Hat Enterprise Virtualization
  • Bonding mode 4 (802.3ad)

  • Cisco Nexus switches.

  • Manageable Switches with lacp support.

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