Recently a client had a problem with some VM’s on its infrastructure. In more detail it was detected that some packets were missing/not transmitting correctly to some virtual servers.
The investigation of the vendor (Cisco) showed that the problem was due to a hard limitation of MAC addresses on the switch. It seemed that a limitation of 70.000 MAC addresses created this problem. But how so many addresses have been created on VMware infrastructure?
In the infrastructure two new chassis with Flex nodes have been added. Those chassis contain around 20 servers each that were included in the virtual Distributed switch. In the vDS existed around 210 VLAN’s. Everytime a new chassis was active on the switch around 3000 new MAC addresses created. This number is approximately the number of VLANs x host number = 20 x 210 = 4200
The problem occurred due to Distributed switch health check mechanism. As VMware states:
vSphere Distributed Switch health check helps you identify and troubleshoot configuration problems with the vSphere Distributed Switch (VDS), and mismatched configurations between the VDS and your environment’s physical network. By default, health check is turned off. You can enable health check to identify and resolve network problems you might be experiencing. Depending on the options that you select, vSphere Distributed Switch health check can generate a significant number of MAC addresses for testing teaming policy, MTU size, and VLAN configuration. These MAC addresses result in extra network traffic, which can affect network performance.
Use health check to troubleshoot network problems, and then disable it after you identify and resolve the problem. After you disable vSphere Distributed Switch health check, the generated MAC addresses age out of your physical network environment according to your network policy. For more information, see Knowledge Base article KB 2034795.
As a result only enable virtual distributed switch health check mechanism for troubleshooting and disable on production environments as it may cause problems on your VM’s.
On previous versions of vcenter server as vsphere 6.5 you had to enable proxy settings through VAMI in order to apply updates on your infrastructure (for non internet facing subnets)
You can locate your appliance VAMI endpoint from https://ApplianceIP/FQDN:5480
However by following the same procedure download manager on vcenter 6.7 was not able to download updates.
By checking the logs I could determine the
Connecting to vapp-updates.vmware.com failed cannot assign requested address.
It seems that download manager is a different component on newer versions and cannot get internet connection through VAMI. You can see below the location on which configuration files and settings are saved inside the vcsa appliance.
In order to resolve issue I added proxy on download manager as shown on the below screenshot and updates could be downloaded.
You can follow the below procedure to extend an RDM disk with virtual compatibility mode on VMware. As described in the article attached on the bottom, you can accomplish that either by migrating the RDM or by shutting down the VM and performing the procedure below. The article implements the shut down way.
The first step is to extend the RDM disk from storage. Find the UUID descriptor and provide some additional space.
Then you need to locate the VMware disk that you want to extend and record the SCSI controller and SCSI ID because it is needed on a later stage.
Then you should delete the disk from virtual machine. You can also select (delete files from datastore) as only the RDM pointer will be deleted and not the actual disk data.
After that you should rescan storage devices and volumes on the ESXi host and locate if the device has identified the new capacity.
Then edit virtual machine settings and select add new device that will be of type RDM Disk
The next dialog shows the new disk with the extended capacity.
Click OK and be careful in order to add the same SCSI ID and controller as previously.
Perform a rescan inside the Operating system and the capacity will be available for use