[SSSD-users] Using SSSD with a forest trust model

Hi.

I have the following scenario : 

-'example.com' domain running on premises
-'aws.example.com' domain running on 'Amazon Microsoft AD' in VPC with VPN
connection to on premises.
- One-way trust created from aws.example.com to example.com 

I´m currently able to log in to a Windows server joined to aws.example.com using
example.com credentials.
Now i want the same for our Linux servers running in Amazon VPC and have tried using this
guide.:
http://docs.aws.amazon.com/directoryservice/latest/admin-guide/join_linux...

I am able to login using credentials from aws.example.com like this .: 
  ssh user(a)aws.example.com (user is present in this domain)
But i am not able to do it using
  ssh user(a)example.com (user is present in this domain)

I have searched a lot on this topic and saw freeipa mentioned a few times, but i would
rather avoid having to use extra software if necessary.

Any help would be greatly appreciated. Please let me know if i need to provide any more
details

Best regards
Kasper