You need at least 250Mbps dedicated vMotion network bandwidth per concurrent vMotion operation.

VMware vSphere ESXi 6.5
VMware vCenter Server 6.0.x
VMware vCenter Server 5.5.x
VMware vSphere ESXi 5.0
VMware vCenter Server 6.5.x
VMware vSphere ESXi 5.5
VMware vCenter Server 6.7.x
VMware vCenter Server 5.0.x
VMware vCenter Server 5.1.x
VMware vSphere ESXi 5.1
VMware vSphere ESXi 6.7
VMware vSphere ESXi 6.0

250Mbps is the minimum required bandwidth for a vMotion migration. For example, to perform two concurrent vMotion migrations, you must provision at least 500Mbps of dedicated bandwidth for the vMotion network.

Greater available bandwidth lets migrations complete more quickly.

Lack of sufficient bandwidth might impact the performance of virtual machine workloads and potentially lead to migration failure.

For idle virtual machines with no running workloads and low memory use, you might be able to complete vMotion migrations even when less dedicated bandwidth is available. However, vMotion is supported only in environments that meet the bandwidth requirement.

WAN optimization techniques, such as compression and deduplication, improve throughput but do not count towards the minimum required bandwidth for vMotion. Gains in throughput resulting from optimization might vary. Even if your environment employs such techniques, you must provision 250Mbps dedicated bandwidth per concurrent vMotion migration.