By default, port 88 and port 750 are used for the KDC, and port 749 is used for the KDC administration daemon. You can use different port numbers. However, if you change the port numbers, then you must change the /etc/services and /etc/krb5/krb5.conf files on every client. In addition, you must update the /etc/krb5/kdc.conf file on each KDC.