Slow or non-working TCP connections over VXLAN with Cisco Systems NICs

Solution Verified - Updated -

Issue

TCP checksums of TCP segments that are encapsulated in VXLAN segments by OVS are incorrect. As a result receiving side is dropping those TCP segments after checking their checksums.

Environment

The issue was found in RHOSP 12, but it is not RHOSP-specific. The following conditions were met:

  • kernel-3.10.0-862.3.2.el7.x86_64
  • openvswitch-2.7.3-3.git20180112.el7fdp.x86_64
  • Cisco Systems Inc VIC 1340 MLOM Ethernet NIC

  • the following NIC settings were configured in Cisco UCS Manager:

    • Receive Side Scaling (RSS)
    • Accelerated Receive Flow Steering
    • Network Virtualization using Generic Routing Encapsulation
    • Virtual Extensible LAN

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