We are on the way decommissioning our BH servers, I ran into issues, and had to move the master role to another server. Doing it is as easy as making a right click and selecting a new server in ESM under routing groups. I am posting TechNet article explaining the routing group master in exchange.
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.
MCITP (EMA), MCITP (SA),
MCSE 2003 M+ S+ MCDST
Security Project+ Server+