Automatic MID Server selection

  • Release version: Zurich
  • Updated July 31, 2025
  • 2 minutes to read
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    Summary of Automatic MID Server selection

    Automatic MID Server selection in ServiceNow enables agents to connect to the most efficient available MID Server by performing connectivity tests based on latency and current agent load. This feature, part of the Agent Client Collector (ACC), is disabled by default and serves primarily as a fail-over mechanism rather than a full load balancer. It dynamically updates the list of MID Servers an agent can connect to without requiring additional workflows, optimizing connectivity and reducing manual configuration efforts.

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    Use Case Considerations

    • Automatic selection narrows down the list of MID Servers available to each agent, streamlining connections.
    • It maintains up-to-date back-end URL configurations on agent hosts automatically.
    • Since it is not a true load balancer, it should be used for fail-over rather than load distribution.
    • The selection process is more complex than using an application load balancer, which requires only a single back-end URL.
    • Agents receive a list of all MID Servers, including those in restricted zones, which might trigger security alerts.
    • DNS configurations can affect the reliability of automatic selection, especially for End User Compute systems switching networks frequently (internal, Wi-Fi, VPN, external).

    Automatic Selection Process

    • ServiceNow periodically sends updates of available MID Servers to agents.
    • Agents select primary and secondary MID Servers, storing them in their configuration for fail-over purposes.
    • If an agent detects an IP address change, it reconnects to the most efficient MID Server from its list.
    • Secure communication between MID Servers and agents is supported via the MID Server unified key store.

    Enabling and Configuring Automatic MID Server Selection

    • Automatic MID Server selection must be explicitly enabled as it is off by default.
    • MID Servers need to be configured with Agent Client Collector capabilities for eligibility in automatic selection.
    • MID Servers can be excluded from agent connections based on criteria like firewall restrictions.

    Practical Benefits for ServiceNow Customers

    Enabling automatic MID Server selection helps optimize agent connectivity by dynamically selecting the best MID Server based on network conditions, reducing manual configuration overhead and improving fail-over resilience. However, customers should evaluate their network environment, security policies, and whether a true load balancer suits their needs better before enabling this feature.

    Automatic selection of MID Servers ensures that each agent uses the most efficient available MID Server.

    The Agent Client Collector automatic MID Server selection feature set is disabled by default. There are several factors to consider before determining if automatic MID Server selection is right for your use cases.

    Use case considerations

    Automatic MID Server selection provides several benefits. can narrow the list of MID Servers an agent can potential connect to. Automatic MID Server selection keeps the back-end URL configuration list up to date on the agent host without additional work flows.

    When automatic MID Server selection is enabled, the agent performs a connectivity test against the list of available MID Servers and determines the best connection based on latency and number of currently connected agents.

    However, there are several additional considerations that may make automatic MID Server selection wrong for your use case.

    The ACC automatic MID Server selection is not a true load balancer and should be considered a fail-over mechanism. There is higher complexity for choosing a back-end URL as it is derived from multiple input sources. If, instead, an application load balancer is used only one back-end URL needs to be specified. See Enable the Agent Client Collector load balancer for more information.

    By default, each agent is sent the list of all MID Servers listening for ACC connections. Since that list includes MID Servers running in restricted areas, the agents can try to connect to them which can generate security alerts.

    Your DNS configuration should be considered before using automatic MID Server selection because the resolution can lead to unexpected results. The DNS resolution is done periodically. End User Compute systems that alternate between internal corporate, Wi-Fi, VPN, or external networks may not be able to reconnect if the network context has changed.

    Automatic selection process

    When automatic selection is enabled, the ServiceNow instance sends periodic MID Server updates to existing agents. The agent selects a MID Server based on information it receives from the ServiceNow instance.

    During automatic MID Server selection, the agent selects a primary MID and a secondary MID list, and writes them to the agent’s config file. The agent uses this list for fail-over protection when the primary MID/secondary MID in the list loses connection.

    When an agent detects that its IP address has changed, it automatically connects with the most efficient MID Server available from the agent's list of MID Servers.

    To secure communication between the MID Server and the agent, use the MID Server's unified key store. For details on using the MID Server unified key store, see MID Server unified key store.