Use only one Domain Controller for Kerberos Authentification

Question

We need to test the Kerberos authentification with only one Domain controllers instead of two.

In my Kerberos Configuration I have the following lines:

[libdefaults]
        default_realm = ABC.ABC.DE

[realms]
        ABC.ABC.DE = {
                master_kdc = ABC01.ABC.ABC.D
                kdc = ABC01.ABC.ABC.DE
                admin_server = ABC01.ABC.ABC.DE
                default_domain = ABC.ABC.DE
        }

Instead of using ABC01.ABC.ABC.DE it is using ABC02.ABC.ABC.DE for the Kerberos authentification.

How can I do it to use only the specified Domain Controller?