You can build complex rule conditions from subexpressions to modify routing policy Session Initiation Protocol (SIP) rules, and route certain messages to servers that are in maintenance mode while routing other traffic to servers that are not in maintenance mode from within the same dynamic cluster.
Typically, only servers that are not in maintenance mode receive and service application requests. You can also route to servers that are in maintenance mode, so you can route to a subset of servers to verify configuration changes or troubleshoot issues without interfering with availability. You can direct SIP traffic to specific clusters with routing rules. The expressions for SIP routing rules are enhanced to support an expression that provides more functionality and flexibility in defining the target cluster. For example, the expression cluster='TestCell/TestClusterA' and serverMaintanceMode='affinity' direct the on demand router (ODR) to route calls to members of TestClusterA that are in maintenance mode. You can also use this function in conjunction with the prioritized routing rules.