The troubleshooting topics about networking in vSphere provide solutions to potential problems that you might encounter with the connectivity of ESXi hosts, vCenter Server and virtual machines. Troubleshooting MAC Address AllocationIn vSphere, certain restrictions on the range of MAC addresses that can be assigned to virtual machines might cause lost of connectivity or inability to power on workloads. The Conversion to the Enhanced LACP Support FailsUnder certain conditions, the conversion from an existing LACP configuration to the enhanced LACP support on a vSphere Distributed Switch 5.5 and later might fail. Unable to Remove a Host from a vSphere Distributed SwitchUnder certain conditions, you might be unable to remove a host from the vSphere distributed switch. Hosts on a vSphere Distributed Switch 5.1 and Later Lose Connectivity to vCenter ServerHosts on a vSphere Distributed Switch 5.1 and later cannot connect to vCenter Server after a port group configuration. Hosts on vSphere Distributed Switch 5.0 and Earlier Lose Connectivity to vCenter ServerHosts on a vSphere Distributed Switch 5.0 and earlier cannot connect to vCenter Server after a port group configuration. Alarm for Loss of Network Redundancy on a HostAn alarm reports a loss of uplink redundancy on a vSphere standard or a distributed switch for a host. Virtual Machines Lose Connectivity After Changing the Uplink Failover Order of a Distributed Port GroupChanges in the failover NIC order on a distributed port group cause the virtual machines associated with the group to disconnect from the external network. Unable to Add a Physical Adapter to a vSphere Distributed Switch That Has Network I/O Control EnabledYou might be unable to add a physical adapter with low speed, for example, 1 Gbps, to a vSphere Distributed Switch that has vSphere Network I/O Control version 3 configured. Troubleshooting SR-IOV Enabled WorkloadsUnder certain conditions, you might experience connectivity or power-on problems with virtual machines that use SR-IOV to send data to physical network adapters. A Virtual Machine that Runs a VPN Client Causes Denial of Service for Virtual Machines on the Host or Across a vSphere HA ClusterA virtual machine sending Bridge Protocol Data Unit (BPDU) frames, for example, a VPN client, causes some virtual machines connected to the same port group to lose connectivity. The transmission of BPDU frames might also break the connection of the host or of the parent vSphere HA cluster. Low Throughput for UDP Workloads on Windows Virtual MachinesWhen a Windows virtual machine in vSphere 5.1 and later transmits large UDP packets, the throughput is lower than expected or is oscillating even when other traffic is negligible. Virtual Machines on the Same Distributed Port Group and on Different Hosts Cannot Communicate with Each OtherUnder certain conditions, the virtual machines that are on the same distributed port group but on different hosts cannot communicate with each other. Attempt to Power On a Migrated vApp Fails Because the Associated Protocol Profile Is MissingYou cannot power on a vApp or virtual machine that you transferred to a data center or a vCenter Server system because a network protocol profile is missing. Networking Configuration Operation Is Rolled Back and a Host Is Disconnected from vCenter ServerWhen you attempt to add or configure networking on a vSphere Distributed Switch on a host, the operation is rolled back and the host is disconnected from vCenter Server.