Migration Manager for Exchange agents and load balancers (4254479)

MS Exch 2010 offers to load balance you MAPI traffic by load balancing your CAS servers in a CAS array, by either Hardware LB or by Windows Network LB.

When a hardware load balancer based CAS array has been properly configured, then all servers in the CAS array are represented by a single virtual IP (VIP) address and by a fully qualified domain name (FQDN). When a client request comes in, it will be sent to an Exchange 2010 CAS server in the CAS array using the DNS round robin distribution method. There are some options to prefer one or more CAS servers over other via features such as weighted round robin, least connection, etc. But the main idea is to load balance you MAPI traffic by load balancing your CAS servers in a CAS array.

This might work perfectly for a day-to-day business, but during the migration lots of data needs to be passed to a specific server (or servers). Basically all existing mail data, which got accumulated during the years, needs to be delivered within a short period of time again. And the MAPI traffic, which has occurred during all the past years, now suddenly needs to happen again, but this time during a very short span or time window, called migration.

Sooner or later the synchronization of mail data will fail, either because the server will reject or truncate the receiving (throttling, load balancing), or simply because the agent will suddenly loose access when being redirected again and again. To avoid this from happening it is recommended to bypass the load balancer, and this needs to be done prior to starting with migration.

A global change would affect all MAPI traffic, including the incoming traffic, and this is often not desired. The easiest way toavoid affecting the production, but at the same time to allow the Quest agents to bypass the load balancer, is to modify the host file on the Agent Host computer.

On the Agent Host machine add the following records to the host file:

CAS_Server_IP   CAS_Array_FQDN

CAS_Server_IP    CAS_ Array_NETBIOS

This CAS_Server_IP cannot be NAT or Dynamic.  Should the IP address change, the host files will have stale records or be pointed to another network endpoint that has taken the lease for the IP address causing Agent Hosts to lose connectivity.

When this has been done confirm that, when pinging the CAS array from this Agent Host machine,  the CAS array resolves to CAS_Server_IP rather than to CAS_Array_IP.

Note: this is not a QMM limitation, this is a native MFCMAPI limitation and the same will happen when using MFCMAPI and trying to reproduce the issue natively.