When choosing to team multiple Web Servers together using a load balancer you must choose a model that is capable of handling session affinity. Also known as “sticky sessions”.
This is because when you logon to MyID the session in IIS is recorded in MyID and maintained for the duration that the client is connected to the system. If anything interrupts the session, such as a failure of the connection, then IIS will create a new session tag the next time a connection is made. This new session tag will not match that which is in MyID and MyID will “assume” that the original connection was broken and this is a new one. The result is that the client will report that the connection to MyID has timed out.
By default, the way load balancers work is to move the session between the servers it is connected to in order to balance the load between the servers. This would result in the above scenario where the client reports a timeout. Unless the load balancer is configured to maintain the session with the web server it first connected to for the entirety of the connection then this could result in a timeout between the client and server.
So before purchasing a load balancer you should check with the vendor that the model you are looking to purchase supports “sticky sessions”.