Every administrator around the world may have problems with the network connection, and the first action to begin the TRBL process is the use of the ping command. Yes, an easy ping can help you, but you have to ping from all directions: ESXi to vCSA and vCSA to ESXi. A typical possible TRBL scenario is when the network is misconfigured, the VLAN is not set up correctly, NIC teaming is not configured correctly, a port on a switch may be down, or there is a hardware problem with a VMNIC or with a physical switch.
The following CLIs can help you identify the problem:
- esxcfg-vswitch
- esxcfg-vmknic
- esxcli network
- esxcfg-nics
In TRBL you must, of course, understand what vSphere Standard Switch (vSS) and vSphere Distributed Switch (vDS) are. The problem can be anywhere, from the virtual machines to the physical network, software, or hardware.
A very good CLI command for TRBL network is esxcli network. For example, a command that can be used to enable or disable a VMNIC is vmnic, followed by the up or down parameters:
esxcli network nic down -n vmnic2
esxcli network nic up -n vmnic2
Network cards can be checked and listed using the esxcli network nic list command:
[root@esxi-prod-1:/] esxcli network nic list
Name PCI Device Driver Admin Status Link Status Speed Duplex MAC Address MTU
Description
------ ------------ -------- ------------ ----------- ----- ------ ----------------- ---- -----------------------------------------------
vmnic0 0000:0b:00.0 nvmxnet3 Up Up 10000 Full 00:50:56:a9:8a:3f 1500 VMware Inc. vmxnet3 Virtual Ethernet Controller
vmnic1 0000:13:00.0 nvmxnet3 Up Up 10000 Full 00:50:56:a9:ac:78 1500 VMware Inc. vmxnet3 Virtual Ethernet Controller
vmnic2 0000:1b:00.0 nvmxnet3 Up Up 10000 Full 00:50:56:a9:2a:5c 9000 VMware Inc. vmxnet3 Virtual Ethernet Controller
vmnic3 0000:04:00.0 nvmxnet3 Up Up 10000 Full 00:50:56:a9:5c:de 9000 VMware Inc. vmxnet3 Virtual Ethernet Controller
vmnic4 0000:0c:00.0 nvmxnet3 Up Up 10000 Full 00:50:56:a9:47:f1 9000 VMware Inc. vmxnet3 Virtual Ethernet Controller
vmnic5 0000:14:00.0 nvmxnet3 Up Up 10000 Full 00:50:56:a9:07:f3 9000 VMware Inc. vmxnet3 Virtual Ethernet Controller
vmnic6 0000:1c:00.0 nvmxnet3 Up Up 10000 Full 00:50:56:a9:93:db 1500 VMware Inc. vmxnet3 Virtual Ethernet Controller
vmnic7 0000:05:00.0 nvmxnet3 Up Up 10000 Full 00:50:56:a9:7c:20 1500 VMware Inc. vmxnet3 Virtual Ethernet Controller
A typical problem that's due to misconfiguration is the selection of a bad virtual machine's port group. Changing to the correct VLAN fixes this problem.
If the management network is misconfigured (the change results in losing the host connection to the vCenter Server), the change is rolled back automatically to the previous configuration.
For additional information, check out VMware KB 2032823: Understanding network rollback and recovery in vSphere 5.1 and later at https://kb.vmware.com/s/article/2032908.