How to know that Active Directory exists with only ip address?

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.NET2.0

C#

.NET

LDAP

, +

How to know that AD exists?

I have only ip address. I tried to use those methods:

if(DirectoryEntry.Exists("LDAP://192.168.1.1"))

also

DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://192.168.1.1")

but it didn't help. I use LdapConnection right now, but I have a problem

LdapConnection connection = new LdapConnection(new LdapDirectoryIdentifier("192.168.1.1"));
                        connection.AuthType = AuthType.Basic;
                        NetworkCredential credential =
        new NetworkCredential("a", '1");

                        connection.Credential = credential;

                        connection.Timeout = new TimeSpan(1000);
                        connection.Bind();

I'm getting 81 code and The LDAP unavailable.

Does somebody know is possible just to know is ip is correct and AD exists?