Vmware

Background In a recent upgrade of our monitoring infrastructure, I moved network monitoring off of physical hardware and onto virtual machines running on our VMware infrastructure. The migration was completely successful except for one small issue: clock drift. One of the many data points we monitor on servers and network gear is whether their configured time is in sync with the rest of the infrastructure. This is done by querying their current time (usually via NTP), and comparing it to the local monitoring server’s clock (also synced via NTP). If the offset is larger than a threshold, an alert is raised. The status of the NTP servers themselves, how many peers, what stratum, etc. is monitored separately. ...

One of my co-workers had provisioned a new appliance VM. It was having connectivity problems, so he asked me to look at it. Upon investigation, I found: absolutely no connectivity: RX Packets 0 on the interface. this was the first/only VM in this VLAN on this vCenter cluster they had just added this VLAN to the dvSwitch for this project So, I first checked what had changed most recently, the dvSwitch config. Everything looked correct. I compared it to other (working) VLANs, and saw no discrepancies. ...

By default VMware virtual machines only PXE boot on first install. Once an operating system has been installed on the hard drive, it will boot that and never try to network boot again. This is due to the default BIOS boot order. By changing the boot order, they can be configured to try a network boot first and after a short timeout boot from disk. In the vSphere client, find the VM in question, and chose Edit Settings. Under VM Options, expand Boot Options and enable the “Force BIOS setup” option. ...