Content Inspection blocked Skype participation in external meetings

Daniel_P30

Currently I have the problem that after activating the content inspection the participation in external Skype meetings is no longer possible. The exception list is adjusted and all skype domains are allowed.
Error Message Connection closing on SSL failure.
Does anyone have a suggestion?

Bruce_Briggs

Have you reviewed the TCP 443 list needed for Skype for Business here?
https://docs.microsoft.com/en-us/microsoft-365/enterprise/urls-and-ip-address-ranges?view=o365-worldwide#bkmk_lyo

There are a list of subnets which are needed - for which you would need to add a HTTPS packet filter To: them

Daniel_P30

Thanks @Bruce_Briggs but it thought the exception list in the content inspection is enough?

Bruce_Briggs

You need to know the SNI or CN of all accesses and have exceptions for them.
You can set up the appropriate logging options on your HTTPS proxy action - Log on Inspect, to see the SNI/CN being accessed when Skipe is being tried and you may find additional SNI/CN entries needed.
Otherwise, add the needed IP addr subnets on a HTTPS packet filter.