Troubleshooting VMware vSphere ESXi Virtual Machine TCP/IP, ping connection issues

Products

• VMware vSphere ESXi

Issue/Introduction

This article provides steps to troubleshoot virtual machine (VM) network communication problems over TCP/IP, ICMP(ping) and other protocols.

Note: ESXi does not log VM connectivity or communication (outside of port or physical link failures seen at the host level), so it is important to perform the troubleshooting steps in this article during the time you are experiencing the issue to be able to determine the cause.

 

• A virtual machine will not ping.
• A TCP/IP connection/service fails to a virtual machine.
• Cannot establish a connection from the virtual machine.
• A virtual machine is no longer pingable or cannot ping other virtual machines.

Environment

VMware vSphere ESXi 7.x
VMware vSphere ESXi 8.x

Resolution

Note: Validate that each troubleshooting step is true for your environment. These steps provide instructions or a link to a document, for validating the step and taking corrective action as necessary. The steps are ordered in the most appropriate sequence to isolate the issue and identify the proper resolution. Do not skip a step.

Troubleshooting virtual machine TCP/IP connection issues

1. Check the VM's network configuration in the guest OS and verify TCP/IP functionality. For more information, see Verifying virtual machine TCP/IP settings.
2. Check for duplicate IP addresses and resolve any TCP/IP stack/driver issues. 
3. Ping another VM that is on the same host, port group and subnet
   1. If ping to another VM on the same host and same port group are not successful then the issue is within the VM itself (in the guest OS or VM adapter settings).
      
      1. Check the the vnic/network adapter of the VM is connected on the virtual switch/vDS on the host
      2. Next ping the loopback address to verify that TCP/IP is working correctly. For more information, see Troubleshooting virtual machine TCP/IP issues by pinging the loopback address.
      3. Check the virtual machine (VM) firewall configuration, or consider disabling the firewall.
      4. Uninstall any suspected third-party antivirus software, or configure it to allow the expected traffic.
   2. If ping to another VM on the same host same port group are successful but not to a VM on different host or different port group, then the issue usually lies in the port group's configuration or in the physical networking. Continue following the troubleshooting steps below.
      1. Verify the default gateway and try to ping it. For more information, see Troubleshooting virtual machine default gateway connection issues .
         
         Note: If connection to the default gateway is successful, but connections to other subnets are unsuccessful, then there is an issue in routing/Layer 3. Contact your network team to determine why the Layer 3 connections are failing.
          
      2. You can also check the esxtop output using the n option (for networking) to see which pNIC the virtual machine is using. Try shutting down the ports on the physical switch one at at time to determine where the virtual machine is losing network connectivity. This also rules out any misconfiguration on the physical switch port(s). If you have a portchannel (not LACP) configured on the physical switchports then IP Hash needs to be set as balancing on the portgroup:  Understanding IP Hash load balancing
      3. Check the virtual switch VLAN configuration. For more information, see VLAN configuration on virtual switches, physical switches, and virtual machines.
      4. Clear the Address Resolution Protocol (ARP) cache. 
      5. Verify physical switch port security. For more information, see Loss of network connectivity when Cisco port security is configured on the physical switch.
4. If the above troubleshooting does not find the answer, use the pktcap-uw tool to packet capture on the physical NIC or on the VM adapter. For more information, see Using the pktcap-uw tool in ESXi 5.5 and later.