An NSX administrator is using ping to check connectivity between VM1 running on ESXi1 to VM2 running on ESXi2. The ping tests fail. The administrator knows the maximum transmission unit size on the physical switch is 1600. Which command does the administrator use to check the VMware kernel ports for tunnel end point communication?

The vmkping command is used on an ESXi host to test network connectivity from a specific VMkernel port. For NSX overlay networking, Tunnel End Points (TEPs) use a dedicated TCP/IP stack, which is geneve in modern NSX versions. The command vmkping ++netstack=geneve correctly targets this stack. The -d option sets the "Don't Fragment" (DF) bit, which is essential for testing the Maximum Transmission Unit (MTU) path. The -s 1572 option sets the ICMP payload size to create a 1600-byte IP packet (1572 payload + 8 ICMP header + 20 IP header), which properly tests the physical network's stated MTU of 1600 between the TEPs.

B. vmkping ++netstack=vxlan -d -s 1572 is incorrect because the vxlan netstack is used for the older NSX-V platform. Current NSX versions, which are the focus of the exam, use the Geneve encapsulation protocol.
C. esxcli network diag ping –H is incorrect because this command does not allow specifying the source VMkernel interface's TCP/IP stack, which is necessary to test connectivity from the TEPs on the geneve stack.
D. esxcli network diag ping -I vmk0 -H is incorrect as it tests from the default TCP/IP stack via a specified interface (likely the management vmk0), not the dedicated geneve stack used for NSX overlay traffic.

1. VMware NSX Documentation, "Verify TEP Connectivity": The official NSX documentation provides the exact command syntax for verifying connectivity between TEPs. It specifies using vmkping ++netstack=geneve and explains the use of the -d and -s flags for MTU validation. The calculation for the packet size (-s - 28) is also detailed. (Reference: VMware NSX-T Data Center Administration Guide, section on "Troubleshoot Overlay Networking").

2. VMware Knowledge Base Article 2129191, "Verifying VXLAN and GENEVE TEP connectivity with vmkping in NSX for vSphere 6.x and NSX-T": This article explicitly outlines the procedure for testing TEP connectivity. It provides the command vmkping ++netstack=geneve -d -s for Geneve tunnels, confirming the syntax and parameters in the correct answer.

3. VMware vSphere Command-Line Interface Reference, "vmkping": The official ESXi command-line documentation details the usage of vmkping, including the ++netstack option to select a specific TCP/IP stack (e.g., geneve, vxlan, vMotion) and the -s and -d options for packet size and fragmentation control. (Reference: vSphere Command-Line Interface Reference, section on Network Commands).