A Solace router (VMR or a physical appliance) maintains two separate types of configuration information:

  • system-level configuration information
  • configuration information for each Message VPN

If you are deploying routers in high-availability (HA) redundant pairs or in replicated data centers, the use of Config-Sync will automatically propagate changes in both types of configurations between two routers, so that they remain in sync.

In both kinds of deployments, Config‑Sync relies on Guaranteed Messaging that must be configured and enabled on each router involved.


  • For redundant appliances that are handling Guaranteed Messaging, durable endpoint information (for example, queue and topic endpoints, topic-to-queue mappings, queue options) is automatically propagated whether Config-Sync is enabled or not.
  • Some configuration parameters that are considered unique to a router or related to licensing or security are not automatically propagated between mates when Config-Sync is enabled. Therefore, they must be manually configured for each router. For more information, see Properties That Are Not Synchronized.

Synchronizing High Availability Deployments

When HA redundancy is used, the configurations of both routers in an HA pair must be the same and remain in sync while the routers are running. The Config-Sync functionality automatically synchronizes configuration of such pairs.

In HA deployments Config-Sync must be instructed which of the paired routers is the master for both the system-level configuration and for each Message VPN-level configuration. This is done by asserting the master configuration over its mate. For each HA pair, the system-level configuration must be asserted, and each Message VPN-level configuration must also be asserted.

Synchronizing Replication Deployments

Config-Sync must be used in replication deployments to synchronize Message VPN-level configuration parameters between replication mates.

When replication is enabled on a router, a replication Config-Sync bridge is automatically created to link a replicated router with its mate, and Message VPNs are automatically synchronized.

For replication deployments, the master Message VPN is always the one with the “Replication Active” state, and any configuration changes made to it are automatically pushed to its corresponding Message VPN in the “Replication Standby” state. Configuration changes are not allowed on the Message VPN in the “Replication Standby” state.

Notice that the Message VPN is also in an HA redundant configuration, its changes are also pushed to the redundant mate routers.

System Resources Used by Config-Sync

The Config-Sync facility consumes additional system resources on a Solace router, specifically it creates and uses:

  • one Message VPN
  • four clients itself and two clients for each synchronized Message VPN
  • nine topic subscriptions for itself and six topic subscriptions for each synchronized Message VPN
  • three queues for itself and two queues for each synchronized Message VPN

It is important to count in the resources listed above as they are limited by system-level limits. See Guaranteed Message Queuing Limits.

All resources created and used by Config-Sync are all named as #config-sync, except for its clients, which are named #config-sync/<router-name>. Any of the resources created and used by Config-Sync cannot be deleted or directly edited.