How to define source IPs from Microsoft Graph service?

Hi,

We need to setup MS Graph webhooks to points to our end points on our own servers. Question is., how this session could be hardened?

Microsoft has published these network lists: Microsoft 365 Common and Office Online 

And on the ID 56, there is the following subnets:

20.20.32.0/19, 20.190.128.0/18, 20.231.128.0/19, 40.126.0.0/18,

Are these the source IPs for what Graph is using?

Or is it the other site Microsoft has published: Other endpoints not included in the Office 365 IP Address and URL Web service

On there they have ID 23 Microsoft Graph Change Notifications. And tons of networks 😄

Also, when the connection is established from Graph to our servers, is there a way to identify the traffic on the header level? E.g. can I set certain GUID which will be always used?

Is there something else what should be taken care?