Re: Windows Slow EAP-TLS Authentication

Azure has a network security feature on by default that drops fragmented UDP packets that arrive out of order. This negatively impacts RADIUS/UDP traffic.

To give you an example, at least 20% of EAP-TLS auth attempts were failing for us in the cert auth phase due to this issue.

Azure support can turn on the 'enable-udp-fragment-reordering' feature by request after providing packet captures and use case info etc. They will also only turn it on in a brand new subscription that's dedicated to running VMs that require this feature. After we did this, our auth success rate increased to 100%.

We had this issue years ago and after several meetings, mails, capture analysis the support just blamed FreeRADIUS…