When working with Active Directory (AD) in a corporate environment, the LDAP connection string typically follows this pattern:

LDAP://{server}:{port}/{distinguishedName}

Key components include:

• Server: Your domain controller's FQDN or IP (e.g., dc1.corp.yourdomain.com)
• Port: Default is 389 (636 for SSL)
• Distinguished Name: The AD path to your container (e.g., DC=corp,DC=yourdomain,DC=com)

Use these PowerShell commands to discover your AD structure:

# Get domain controllers
Get-ADDomainController | Select-Object HostName,IPv4Address

# Get default naming context
$rootDSE = [ADSI]"LDAP://RootDSE"
$rootDSE.defaultNamingContext

Here are typical patterns you might use:

// Basic authentication
LDAP://dc1.corp.example.com:389/DC=corp,DC=example,DC=com

// SSL connection
LDAPS://dc1.corp.example.com:636/OU=Users,DC=corp,DC=example,DC=com

// Using domain name (Windows will resolve)
LDAP://corp.example.com/DC=corp,DC=example,DC=com

For the Active Directory Membership Provider:

// In Web.config
<connectionStrings>
  <add name="ADService" 
       connectionString="LDAP://corp.example.com/DC=corp,DC=example,DC=com" />
</connectionStrings>

<system.web>
  <membership defaultProvider="AspNetActiveDirectoryMembershipProvider">
    <providers>
      <add name="AspNetActiveDirectoryMembershipProvider"
           type="System.Web.Security.ActiveDirectoryMembershipProvider"
           connectionStringName="ADService"
           connectionUsername="corp\serviceaccount"
           connectionPassword="p@ssw0rd" />
    </providers>
  </membership>
</system.web>

• Ensure port 389/636 is open in your firewall
• Verify DNS resolution for your domain controllers
• Check service account permissions in AD
• Use ldp.exe tool to test basic connectivity

For multi-domain forests:

LDAP://ForestRootDomain/DC=forestroot,DC=com

Or use GC (Global Catalog) port 3268 for forest-wide searches:

GC://corp.example.com:3268/DC=corp,DC=example,DC=com

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When working with Active Directory (AD) in a corporate environment, establishing an LDAP connection is often the first step. LDAP (Lightweight Directory Access Protocol) is the protocol used to interact with directory services like AD. The connection string is crucial for authentication, querying, and other directory operations.

A typical LDAP connection string for Active Directory includes the following components:

• Server/Host: The domain controller (DC) or LDAP server address.
• Port: Usually 389 for LDAP or 636 for LDAPS (secure LDAP).
• Base DN: The distinguished name (DN) of the root of your directory tree.
• Authentication Details: Username and password for binding.

Here's how you can discover these components in a corporate AD environment:

1. Locating the Domain Controller

You can use the nslookup command to find your domain controllers:

nslookup -type=SRV _ldap._tcp.dc._msdcs.<your-domain-name>

Replace <your-domain-name> with your actual domain (e.g., corp.example.com). This will return the SRV records pointing to your domain controllers.

2. Determining the Base DN

The Base DN typically follows this pattern:

DC=corp,DC=example,DC=com

You can also discover this by:

dsquery * -filter "(objectClass=domain)" -attr distinguishedName

Here are some common formats:

Basic LDAP Connection

LDAP://dc1.corp.example.com:389/DC=corp,DC=example,DC=com

Authenticated Connection

LDAP://dc1.corp.example.com:389/DC=corp,DC=example,DC=com;uid=username,ou=users,dc=corp,dc=example,dc=com;password

Secure LDAP (LDAPS)

LDAPS://dc1.corp.example.com:636/DC=corp,DC=example,DC=com

Here's a simple C# example to test your LDAP connection:

using System.DirectoryServices;

try {
    DirectoryEntry entry = new DirectoryEntry(
        "LDAP://dc1.corp.example.com:389/DC=corp,DC=example,DC=com",
        "username@corp.example.com",
        "password");
    
    DirectorySearcher searcher = new DirectorySearcher(entry);
    searcher.Filter = "(objectClass=user)";
    SearchResult result = searcher.FindOne();
    
    Console.WriteLine("Connection successful!");
}
catch (Exception ex) {
    Console.WriteLine("Error: " + ex.Message);
}

If you're having connection problems:

• Verify network connectivity to the domain controller
• Check if the port is open (try telnet to port 389 or 636)
• Ensure your credentials have proper permissions
• Verify the certificate if using LDAPS

For applications using membership providers, you can configure the connection in web.config:

<connectionStrings>
    <add name="ADConnectionString" 
         connectionString="LDAP://dc1.corp.example.com:389/DC=corp,DC=example,DC=com" />
</connectionStrings>

<membership defaultProvider="AspNetActiveDirectoryMembershipProvider">
    <providers>
        <add name="AspNetActiveDirectoryMembershipProvider"
             type="System.Web.Security.ActiveDirectoryMembershipProvider"
             connectionStringName="ADConnectionString"
             connectionUsername="username@corp.example.com"
             connectionPassword="password" />
    </providers>
</membership>