Communications fail between Azure Load Balancer and SLE instance

This document (7024034) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server for Azure

Situation

Communications fail to Public Cloud instance through the Azure Load Balancer.

Resolution

Disable net.ipv4.tcp_timestamps setting.

In-memory change:

hostname:~ # echo 0 > /proc/sys/net/ipv4/tcp_timestamps

Persistent change:

  1. Create a tcp_timestamps.conf drop-in configuration file.

    hostname:~ # echo "net.ipv4.tcp_timestamps = 0" > /etc/sysctl.d/tcp_timestamps.conf

  2. Load new sysctl parameter from configuration file.

    hostname:~ # sysctl -p /etc/sysctl.d/tcp_timestamps.conf


CAUTION: Certain application workloads and HPC features require tcp_timestamps.  When in doubt, consult the manual or other technical resources to be sure disabling this setting will not negatively impact the running application(s).  If the application requires this parameter, use of the Azure Load Balancer is not recommended.

Cause

With TCP Timestamps enabled, health probe packets sent through the Azure Load Balancer may be dropped by the guest OS, causing the load balancer to report the endpoint as down.

Full explanation can be found at the bottom of the "Design guidance" section here:

Additional Information


Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:7024034
  • Creation Date: 25-Jul-2019
  • Modified Date:03-Mar-2020
    • SUSE Linux Enterprise Server

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