vSphere 6.0: Troubleshooting vDistributed Switch Issues (Part-9)

Learning, configuring, and troubleshooting vSphere Networking is the most important aspect of managing VMware virtual environment. In pervious post of this series, we learned how VMKernel Networking adapter is created on a host associated with a distributed switch (vDS) to handle the standard system traffic for vMotion, IP Storage (iSCSI, NAS), Fault Tolerance logging, vSAN, and others. In this post, we’ll see some common troubleshooting issues with distributed switch and how we can resolve them. If you missed previous posts virtual networking series, you can follow:

  1. Introduction to vSphere Standard Switch (vSS)
  2. How to Create Standard Switch (vSS)
  3. Configuring vSphere Standard Switch Policies
  4. Introduction to vSphere Distributed Switch
  5. Creating vSphere Distributed Switch
  6. Adding ESXi Hosts to vSphere Distributed Switch
  7. About the VMKernel Networking Level
  8. Create a VMKernel Adapter on a vDS

Troubleshooting Issues

One of some issues which often vSphere administrators face is the VMs on the same distributed port group but on the different hosts can’t communicate with each other. Ping from one VM to another fails, and VMs can’t be migrated from one host to another via vMotion.

The main cause of this can be on some hosts, no physical NICs are assigned to active or standby uplinks in a NIC teaming, or the failover order of a distributed port group is not properly configured. Or it may be physical NICs on the hosts are assigned to the active or standby uplinks reside on different VLANs on the physical switch. The physical NICs on different VLANs are not visible to one another and thus fails to communicate.

Solution

To solve the basic troubleshooting issue, check that which host does not have physical NICs assigned to an active or standby uplink on the distributed port group. Assign at least one physical NIC on that host to an active uplink to the distributed port group. Check the VLAN IDs of the physical NICs assigned to the active uplinks on the port group. On all hosts, assign physical NICs from the same VLAN to an active uplink on the distributed port group.

Physical Network Considerations

Virtual networking environment relies on the physical network infrastructure. As a vSphere administrator, your vSphere networking requirements should be discussed with the network administration team.

                                          Figure: Thanks to packetpub.com

Following issues can be discussed with the network administration team:

  • Physical switch configuration support for 802.3ad, for NIC teaming
  • Physical switch configuration support for 802.3Q, for VLAN tagging
  • Physical switch configuration support for Link Aggregation Control Protocol (LACP)
  • Number of physical switches
  • Network bandwidth required for network management
  • Network port security
  • Link Layer Discovery Protocol (LLDP), Cisco Discovery Protocol (CDP) and their operation modes such as listen, broadcast, listen and broadcast, and disable

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