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Proofpoint, Inc.

CIDR Breakdown for and


You are setting up your account with Office 365 and need to know the CIDR ranges.

  • Not able to use /22 range
  • Office 365 only accepting CIDR range up to /24
Solution If setting up CIDR ranges but not able to use /22 these can be further broken down and used in /24 CIDR.


For customers who are using Office 365 or any other platform that will only accept CIDR format ranges of /24