Troubleshooting VM Network Connectivity Issues with VLAN Tagging on ESXi 8.0
Article ID: 451775
Updated On:
Products
VMware vSphere ESXi
Issue/Introduction
Virtual machines on an ESXi host may experience network connectivity issues where communication works between VMs on the same host and port group, but fails to traverse the physical network to external gateways or other hosts. This article provides troubleshooting steps for environments configured with 802.1Q VLAN tagging.
Environment
VMware vSphere ESXi 8.0 and higher.
Cause
Connectivity issues frequently arise from a mismatch between the Virtual Switch (vSwitch/vDS) port group VLAN configuration and the physical switch port configuration. This often occurs when:
- Physical switch ports are configured as trunked, but the physical port does not have the corresponding VLAN tag from the vSphere port group allowed.
- The vSphere port group has a VLAN tag assigned, but the physical switch ports are configured with the same number as the native vlan, causing the vSwitch to drop the untagged ingress packet.
Resolution
Verify Virtual Switch / Port Group Configuration:
- In the vSphere Client, select the ESXi host > Configure > Virtual Switches.
- Identify the port group used by the affected VM.
- Verify the VLAN ID assigned to the port group. Ensure it matches the VLAN ID expected/allowed by the physical network port for that traffic.
- Verify the VLAN ID assigned to the port group does not match the native VLAN ID for the physical network port.
Verify Physical Switch Configuration:
- Identify the physical NICs (vmnics) used as uplinks for the vSwitch.
- Work with your networking team to confirm that the physical switch ports connected to these vmnics are configured as trunk ports and have the required VLANs allowed.
- Verify the VLAN ID assigned at the port group does not match the native VLAN ID for the physical network port.
Additional Information
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