Provided is a system having a cluster of communication controllers, a method for modification of the latter, and a computer program product carrying computer executable code for execution of the method. Each communication controller is operable for providing network connections of the system with external computer systems using communication protocols of a first type and a second type. The first type is a failover tolerant communication protocol type. The second type is a failover non-tolerant communication protocol type. All network connections of each communication controller are disconnected during the modification of said communication controller. The method for modifying the cluster of communication controllers includes splitting the communication controllers into a first pool and a second pool.