<div>
Not sure what server OS etc your running but you may want to review the following article and see if it applies to your situation. <br />
<br />
<a href="https://support.microsoft.com/en-us/help/2675498/netbios-domain-name-username-format-cannot-be-used-with-the-kerberos-r" rel="ugc">https://support.microsoft.com/en-us/help/2675498/netbios-domain-name-username-format-cannot-be-used-with-the-kerberos-r</a>
</div>


Not sure what server OS etc your running but you may want to review the following article and see if it applies to your situation.

https://support.microsoft.com/en-us/help/2675498/netbios-domain-name-username-format-cannot-be-used-with-the-kerberos-r [https://support.microsoft.com/en-us/help/2675498/netbios-domain-name-username-format-cannot-be-used-with-the-kerberos-r]

<div>
<blockquote>
Is that typical or is there anything we can do to make the login domain not require the .com?
</blockquote>
No, not typical
</div>


> Is that typical or is there anything we can do to make the login domain not require the .com?

No, not typical

<div>
<div class="content wysiwyg-content">
We recently configured a forest trust between two domains and we have been able to cross authenticate. &nbsp;However, it only works if the user puts in domain.com\username. &nbsp;It isn't enough to just put in domain\username.<br />
<br />
The scenario looks like this.<br />
<br />
User at company.b.com is logging into a server at company.a.com. &nbsp;To use the username and password for their compay.b.com account they need to log into the server as company.b.com\username.<br />
<br />
Is that typical or is there anything we can do to make the login domain not require the .com?<br />
<br />
Is there something else we can do in DNS to allow this to work?
</div>
</div>


We recently configured a forest trust between two domains and we have been able to cross authenticate.  However, it only works if the user puts in domain.com\username.  It isn't enough to just put in domain\username.

The scenario looks like this.

User at company.b.com is logging into a server at company.a.com.  To use the username and password for their compay.b.com account they need to log into the server as company.b.com\username.

Is that typical or is there anything we can do to make the login domain not require the .com?

Is there something else we can do in DNS to allow this to work?

Cross domain authentication requiring domain.com\username for login

Trust Relationships

The Domain Name System (DNS) is a hierarchical, globally distributed system responsible for associating the name of a computer, service or other resource into an IP address for connecting to the Internet or a private network. Most prominently, it translates domain names to the numerical IP addresses needed for the purpose of computer services and devices worldwide.

Active Directory (AD) is a Microsoft brand for identity-related capabilities. In the on-premises world, Windows Server AD provides a set of identity capabilities and services, and is hugely popular (88% of Fortune 1000 and 95% of enterprises use AD). This topic includes all things Active Directory including DNS, Group Policy, DFS, troubleshooting, ADFS, and all other topics under the Microsoft AD and identity umbrella.