Unlike
the Hub Transport server, which automatically load balances between
them (due in part to Active Directory), the Edge Transport servers do
not have this capability.
You
can deploy multiple Edge Transport servers and then use DNS MX (Mail
Exchanger) records to ensure the Edge Transport servers have the load
balancing aspect, and at the same time, if one fails, there is another
to keep messaging flowing in and out of your organization.
In
the case of Unified Messaging servers, the concept is similar. Deploy
multiple servers where two or more are in the same dial plan. For load
balancing, you can configure your VoIP gateways to route calls in a
round-robin method, so that if a call is not accepted by a server (in
the event it has gone down or is out for maintenance), the call is sent
to another UM server.
