Virtual Machines Lose Connectivity After Changing the Uplink Failover Order of a Distributed Port Group

Changes in the failover NIC order on a distributed port group cause the virtual machines associated with the group to disconnect from the external network.

Problem

After you rearrange the uplinks in the failover groups for a distributed port group in vCenter Server, for example, by using the vSphere Web Client, some virtual machines in the port group can no longer access the external network.

Cause

After changing the failover order, many reasons might cause virtual machines to lose connectivity to the external network.

• The host that runs the virtual machines does not have physical NICs associated with the uplinks that are set to active or standby. All uplinks that are associated with physical NICs from the host for the port group are moved to unused.
• A Link Aggregation Group (LAG) that has no physical NICs from the host is set as the only active uplink according to the requirements for using LACP in vSphere.
• If the virtual machine traffic is separated in VLANs, the host physical adapters for the active uplinks might be connected to trunk ports on the physical switch that do not handle traffic from these VLANs.
• If the port group is configured with IP hash load balancing policy, an active uplink adapter is connected to a physical switch port that might not be in an EtherChannel.

You can examine the connectivity of the virtual machines in the port group to associated host uplinks and uplink adapters from the central topology diagram of the distributed switch or from the proxy switch diagram for the host.

Solution

• Restore the failover order with the uplink that is associated with a single physical NIC on the host back to active.
• Create a port group with identical settings, make it use the valid uplink number for the host, and migrate the virtual machine networking to the port group.
• Move the NIC to an uplink that participates in the active failover group.
  You can use the vSphere Web Client to move the host physical NIC to another uplink.
  • Use the Add and Manage Hosts wizard on the distributed switch.
    1. Navigate to the distributed switch in the vSphere Web Client.
    2. From the Actions menu select Add and Manage Hosts.
    3. On the Select task page, select the Manage host networking option and select the host.
    4. To assign the NIC of the host to an active uplink, navigate to the Manage physical network adapters page and associate the NIC to the switch uplink.
  • Move the NIC at the level of the host.
    1. Navigate to the host in the vSphere Web Client, and on the Configure tab, expand the Networking menu.
    2. Select Virtual Switches and select the distributed proxy switch.
    3. Click Manage the physical network adapters connected to the selected switch, and move the NIC to the active uplink