Question 61 - NCP-MCI-6.5 discussion

The correct answer is C. The VLAN was not created on the upstream switches.

A VLAN (virtual local area network) is a logical segmentation of a physical network that allows devices on the same VLAN to communicate with each other, regardless of their physical location. A VLAN also isolates the devices on different VLANs from each other, unless there is a router or a layer 3 switch that can route traffic between VLANs. To create a VLAN, the administrator needs to configure the network devices that are involved in the VLAN, such as switches, routers, and hosts. The administrator also needs to assign a unique VLAN ID to each VLAN, which is a number between 1 and 4094 that identifies the VLAN1.

In Nutanix AHV, the administrator can create a Nutanix managed network with a specific VLAN ID for guest VMs. This network can be assigned to VM NICs using Prism Element or Prism Central. However, creating a Nutanix managed network does not automatically create the VLAN on the upstream switches that connect the AHV hosts. The administrator needs to manually configure the upstream switches to allow the VLAN traffic on the ports that connect to the AHV hosts. The administrator also needs to ensure that the upstream switches are interconnected physically or virtually and can forward traffic between different VLANs if needed2.

Therefore, if an administrator has created a Nutanix managed network with a VLAN ID of 512 and notices that the VMs on that network can only communicate with other VMs on the same host, but not with VMs on different hosts in the cluster, the most likely cause of this issue is that the VLAN was not created on the upstream switches. This means that the switches are dropping or blocking the traffic with VLAN ID 512 and preventing it from reaching other hosts or VMs. To resolve this issue, the administrator should create the VLAN on the upstream switches and allow it on the ports that connect to the AHV hosts3.