Managing a communications network involves allocating hosts (100) for instances (105) of a virtual network function component (155). From a request to allocate, a number N is obtained indicating a minimum number of the instances to be available, and a number M indicating how many additional instances are to be allocated. If the allocations are requested to be to different hosts (anti affinity) and if the sharing of the instances by the virtual network function component can be adapted in the event of unavailability, then allocating is carried out automatically (230) of N+M of the instances to less than N+M of the hosts, so that if any one of the allocated hosts becomes unavailable there are sufficient hosts so that the virtual network function component can still be shared across at least N of the instances. Fewer hosts are needed, saving costs.