According to an example, a method for bandwidth guarantee and work conservation includes determining virtual machine (VM) bandwidth guarantees assigned to VMs in a network including a source VM that communicates with destination VMs. The method further includes assigning minimum bandwidth guarantees to communications between the source VM with the destination VMs by dividing a VM bandwidth guarantee assigned to the source VM between the destination VMs based on active VM-to-VM communications between the source VM and the destination VMs. The method also includes allocating, by a processor, spare bandwidth capacity in the network to a communication between the source VM and a destination VM based on the assigned minimum bandwidth guarantees.