Hi Andy,

yes, the API endpoint between servers is at umbraco/uSyncReceive so this will need to be something servers can see on the other servers.

you should see something at the end of the web.config for this -

  <location path="umbraco/uSyncReceive">
    <!-- Up the file upload limit to 500mb, this is for moving media around -->
    <system.web>
      <httpRuntime maxRequestLength="512000"/>
    </system.web>
    <system.webServer>
      <security>
        <!-- Restrict API access by IP - you can here restrict so only servers can talk to each other -->
        <!--
        <ipSecurity allowUnlisted="false">
          <add allowed="true" ipAddress="192.168.0.1" subnetMask="255.255.255.0" />
          <add allowed="true" ipAddress="127.0.0.1" subnetMask="255.255.255.0" />
        </ipSecurity>
        -->
        <requestFiltering>
          <requestLimits maxAllowedContentLength="524288000" />
        </requestFiltering>
      </security>
    </system.webServer>
  </location>

this gives you a space to restrict by IP etc.