Designating a Routing Group Master
When you create a routing group, the first server in that routing group is assigned the role of routing group master. The routing group master maintains current link state information for its routing group and propagates it to the other servers within the routing group. The routing group master monitors the routing configuration that is written in Active Directory for its routing group only. Member servers can communicate any connector state or server availability information to the routing group master. For example, if a member server tries to contact another server in a different routing group over a connector, and this link is unavailable, the member server immediately notifies the routing group master. Likewise, when a non-master server receives new link state information, it immediately transfers the connector state information to the routing group master, so that other servers can receive the information about the routing change.
When you designate a routing group master, ensure that the server you choose has good access to a domain controller because this is where it reads the configuration information that is stored in Active Directory. Additionally, when a change occurs in the configuration of its routing group, Exchange System Manager writes this information directly to Active Directory and then the domain controller notifies the routing group master of this change. The routing group master then propagates this information to all the member servers.
Within a routing group, the routing group master and the other Exchange servers communicate link state information over TCP/IP port 691. However, communication of link state information between routing groups is different. If the routing group master is not a bridgehead server for the routing group, the routing group master sends the link state information to the group's bridgehead server over TCP/IP port 691. The bridgehead server then forwards this information (over TCP/IP port 25 using SMTP and the X-LINK2STATE verb) to the bridgehead servers of other routing groups.
Note
For more information about link information and how it is updated, see Advanced Link State Concepts.
If you do not want the first server that is installed in the routing group to be the routing group master (the default setting), you can change the routing group master to another server by using the following procedure.
Note
Do not change the routing group master frequently. When you designate a new routing group master, all member servers need to reconnect and this change requires that the link state table replicate across the organization, which increases network traffic.
For detailed instructions about how to change the routing group master, see How to Change Which Server Is the Routing Group Master.
Important
There is no automatic failover for routing group masters. If a routing group master fails, you must manually configure a new routing group master in Exchange System Manager. If a routing group master fails, the other servers in the routing group use the last known link state information until a routing group master becomes available or another routing group master is designated. For more information about failure of a routing group master, see Microsoft Knowledge Base article 261827, "https://go.microsoft.com/fwlink/?linkid=3052&kbid=261827."