We're having an issue getting sssd to lookup non-qualified names across our forest. From the documentation it appears this should be supported via lookups done to the global catalog or failing that, queries against all discovered subdomains. 

- Two domains, site.com and b.site.com
- Host is joined to b.site.com., and is joined to the domain (net ads join)
- Users that will login can be found in either b.site.com and site.com
- usernames and uid's are unique within the forest

What works:
- login and lookup for accounts in b.site.com
- login and lookup for site.com accounts when fully qualified (user@site.com)

Desired behavior:
- users from site.com can use their non-qualified usernames to connect to the host

Current Config:
domains = b.site.com
config_file_version = 2
override_space = _
services = nss,pam

debug_level = 9
ldap_group_nesting_level = 5
id_provider = ad
auth_provider = ad
default_shell = /bin/bash
ldap_id_mapping = false
simple_allow_groups = groupa@site.com
use_fully_qualified_names = false
ad_enable_gc = true

Other notes:
- We attempted to use the setup described here https://lists.fedorahosted.org/pipermail/sssd-users/2015-February/002648.html, however clients attempt to authenticate to each domain and fail as they are only joined to b.site.com
- Made sure the following attributes were replicated to the global catalog: uidNumber,gidNumber,loginShell,unixHomeDirectory
- logs show that an ldap query is only attempted against b.site.com for the non-qualified account.
- logs show that the root domain, site.com is discovered along w/ its domain controllers.
- version 1.13.4 (ubuntu 16.04)

Any suggestions?