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Windows VM Activation Problems Behind pfSense

If your Windows virtual machines cannot activate, it is usually because pfSense cannot find the KMS server.

What to do:

  • Make sure pfSense can resolve _vlmcs.synapsecom.gr.
  • Add a DNS record or host override in pfSense that points _vlmcs.synapsecom.gr to the correct server IP (78.108.44.3).
  • After this, Windows VMs should activate normally.

Note

  • The _vlmcs.synapsecom.gr server is official and only works inside Synapsecom networks.
  • The underscore _ at the start is important — don’t remove it.
  • If your VMs still don’t activate, check that pfSense DNS is working correctly.