I am trying to figure how to get Multi-Domain user authentication using Windows Authentication. We are currently on version 4.82 of DNN and  I thought Active Directory  would work and take care of this as long as the other domains groups were setup to match Windows AD.

Multi-Domain has always been a problem that I haven't been able to code for (mainly because I don't have access to a multi-domain environment). My suggestion is to try seeing if you have access to the other domains using LDAP Browser (http://www.ldapbrowser.com/download).

I modified the Login.ascx for multiple domains. I hope it helps.

<code>
<%@ Control language="vb" Inherits="DotNetNuke.Authentication.ActiveDirectory.Login, DotNetNuke.Authentication.ActiveDirectory" AutoEventWireup="false" Explicit="True" Codebehind="Login.ascx.vb" %>
<%@ Register TagPrefix="dnn" Assembly="DotNetNuke" Namespace="DotNetNuke.UI.WebControls"%>
<%@ Register TagPrefix="dnn" TagName="Label" Src="~/controls/LabelControl.ascx" %>

<script type="text/javascript">
function checkInput()
{
 var Proceed = 1;
 var Message;
    var usrname = document.getElementById('txtUsrname');
    var password = document.getElementById('<%= txtPassword.ClientID %>');
    var cboDomain = document.getElementById('cboDomain');

 while (Proceed == 1)
 {
  if (!usrname.value) {
   Message = "Please enter Username.";
   Proceed = 0;
   break;
  }
  if (!password.value) {
   Message = "Please enter Password.";
   Proceed = 0;
   break;
  }
  if (cboDomain.selectedIndex == 0 ) {
   Message = "Please select Domain.";
   Proceed = 0;
   break;
  }

  break;
 }

 if (Proceed == 1) {
  return true;
 }
 else {
   Message );
  return false;
 }
}

function validateLogin()
{
    var username = document.getElementById('<%= txtUsername.ClientID %>');
    var btn = document.getElementById("<%= cmdLogin.ClientID %>");
    var usrname = document.getElementById('txtUsrname');
    var cboDomain = document.getElementById('cboDomain');

    if (checkInput())
    {
    username.value = cboDomain.options[cboDomain.selectedIndex].value + "\\" + usrname.value;
    // cboDomain.options[cboDomain.selectedIndex].value + "\\" + usrname.value);

    btn.click();
    }
}
</script>

<table cellspacing="0" cellpadding="3" border="0" summary="SignIn Design Table" width="160">
 <tr>
  <td class="SubHead" align="center"><dnn:label id="plUsername" controlname="txtUsername" runat="server" text="UserName:"></dnn:label></td>
 </tr>
 <tr>
  <td  align="center">
  <asp:textbox id="txtUsername" width="0" Style="visibility:hidden;" runat="server" />
     <input type="text" id="txtUsrname" class="NormalTextBox" /></td>
 </tr>
 <tr>
  <td class="SubHead" align="center"><dnn:label id="plPassword" controlname="txtPassword" runat="server" text="Password:"></dnn:label></td>
 </tr>
 <tr>
  <td align="center"><asp:textbox id="txtPassword" columns="9" width="130" textmode="password" cssclass="NormalTextBox" runat="server" /></td>
 </tr>
 <tr>
  <td class="SubHead" align="center"><dnn:label id="plDomain" controlname="auth" runat="server" text="Domain:"></dnn:label></td>
 </tr>

 <tr>
        <td align="center">
            <select name="cboDomain" class="NormalTextBox">
                <option value="">- Please Select -</option>
                <option value="First">First Domain</option>
                <option value="Second">Second Domain</option>
                <option value="Third">Third Domain</option>
            </select>
        </td>
 </tr>

    <tr id="trCaptcha1" runat="server">
     <td class="SubHead" align="center"><dnn:label id="plCaptcha" controlname="ctlCaptcha" runat="server" text="Password:"></dnn:label></td>
    </tr>
    <tr id="trCaptcha2" runat="server">
     <td align="center"><dnn:captchacontrol id="ctlCaptcha" captchawidth="130" captchaheight="40" cssclass="Normal" runat="server" errorstyle-cssclass="NormalRed" /></td>
    </tr>
    <tr>
     <td id="tdLogin" runat="server" align="center">
     <asp:button id="cmdLogin" Style="visibility:hidden;" runat="server" />
        <input id="cmdLgin" type="button" value="Login" class="StandardButton" onclick="validateLogin();" />
     </td>
    </tr>
</table>
</code>