How to Reset Device Trust – F5 LTM Load Balancing Methods Troubleshooting ConfigSync and Device Clustering

Chris Spillane provides a quick guide to troubleshooting device clustering or config sync for version 11.x.

Notice: This blog post was originally published on Indeni before its acquisition by BlueCat.

The content reflects the expertise and perspectives of the Indeni team at the time of writing. While some references may be outdated, the insights remain valuable. For the latest updates and solutions, explore the rest of our blog

Key Takeaways
  • In F5 BIG-IP v11.x, device clustering and configuration sync rely on communication between the mcpd and tmm processes across peer devices.
  • The local mcpd process connects to the local tmm process on port 6699 to initiate the device cluster formation.
  • The local tmm process then contacts the peer device’s config sync IP on port 4353 to continue the clustering handshake.
  • Upon receipt, the peer device’s tmm process connects to its local mcpd process on port 6699, completing the mcpd-to-mcpd mesh.
  • If any step in this communication sequence fails, the BIG-IP system automatically retries the process every five seconds.
  • The “local machine” used for config sync is the self IP defined for config sync under Device Management > Devices > Device Connectivity > Config Sync.

F5 LTM Load Balancing Methods: How to Reset Device Trust.

The official F5 SOL13946 provides information on troubleshooting device clustering and configuration sync for 11v  F5 load balancers  and other products, however it is rather long winded.  This guide is designed as a quick reference when troubleshooting device clustering or config sync. An overview of the config sync process for version 9.x and 10.x units can be found in F5 SOL7024

Version 11.x

  • Communication between machines occurs in the following manner to form a device cluster:

    mcpd process on the local machine connects to the tmm process on the local machine on port 6699

  • tmm process then contacts the peer’s config sync IP on port 4353
  • Once the peer receives, they use tmm to contact mcpd over port 6699 on their local device.
  • If this process fails, it is re-attempted every 5 seconds.
  • If this process succeeds, there is a mesh between peer mcpd processes.

* local machine here refers to the self IP configured for config sync. Check it under Device Management > Devices > click on device > Device Connectivity > Config Sync, for example.

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