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How to fix a vCenter Appliance No-Networking problem

This problem might occur with your vCenter Server Appliance. But it could also happen with other Linux-servers. It might happen when you move the virtual machine, clone it, restore it, recover it from replication or perform any other action where the MAC Address of the virtual machine changes. This is what you would see on the console of the virtual appliance:

vCenter Appliance No Networking error

In other Linux-servers you could identify this problem when your Linux-OS does not have a valid configuration for the network adatper (eth0). Test this with the ifconfig command.

The problem occurs because SUSE Linux Enterprise Server 11, which is the OS for the appliance, stores the network card configuration for adapter eth0 in the udev-rules based on the MAC Address. So when that address changes it breaks this assignment. What actually happens is that a new adapter is detected and becomes device eth1. In the image below you can see the contents of the udev rules file: 

vCenter Appliance No Networking error

When we look at the second line in this example and compare the MAC Address with the address that the VM has in the vSphere Client or Web Client then you see that it matches the eth1 configuration. And since the IP Address configuration was assigned to eth0 your machine no longer has a valid networking configuration.

vCenter Appliance No Networking error

There are two approaches to this problem. One is to modify the MAC Address if you are certain that it is not in use, but the simplest one is to remove all the rules and then restart your system which will detect the current adapter as eth0 and assign the correct IP configuration to your device. Then the services (vCenter) will load and use the correct IP configuration.

Edit the following file:

/etc/udev/rules.d/70-persistent-net.rules

(If you need instructions on using the VI-editor please read this article.)

Remove the lines described previously so that your file looks like this:

vCenter Appliance No Networking error

Next restart your machine and during boot you will see that a valid eth0-configuration exists.

vCenter Appliance No Networking error

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