Guest VM losing network connectivity

Hi folks,

We’re running VMWare 6.7, no major problems as we build out a small lab network.

Each day when I come in, the CentOS server we run Splunk on loses it’s connection to the network. When I ping another guest host from it, after 5 seconds or so it comes back up.

Anyone seen a problem like this?

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  1. Ping fixing it makes me think either IP a conflict or an issue with arp learning. Are all the VMs in the same subnet?

    While the connectivity is broken, ping the VM from a vm on the same subnet and check the arp table on the vm you’re pinging from, check that the ip is listed and that it’s MAC address is correct.

    If the IP is not listed, or shows incomplete there is something causing ARP to fail, if it is listed with the wrong MAC then there’s an ip conflict

    I’d also recommend running packet captures on both the splunk server and on the vm pinging the server then open them up in wireshark and look for arp requests, you should see the vm showing “who has <ip address>” and the server should be replying with “<ip address> is at <MAC address of server>”

  2. Do you have VLAN and MTU Health Checks enabled? If not, is it possible that one of your hosts may have this VM’s VLAN configured differently from the other hosts, and it just happens to vMotion to a working host when you fire things up in the morning?

  3. What version of 6.7 are you using?
    We ran into a similar issue with VMXNET3 drivers getting HEAP overrun on the hosts. Worked with GSS and 6.7 u3 has been patched and has resolved our issue.

    * The maximum memory heap size for any module is 3 GB. If the requested total memory size is more than 4 GB, an integer overflow occurs. As a result, the MAC addresses of the virtual machine interfaces are set to 00:00:00:00:00:00 and the VMXNET3 device might fail to start. In the VMkernel log, you might see an error similar to: Vmxnet3: 15204: Failed to allocate memory for tq 0.

    [Link to 6.7 U3 Release Notes](https://docs.vmware.com/en/VMware-vSphere/6.7/rn/vsphere-esxi-67u3-release-notes.html)

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