Changing the LDAP port number in xchg 2k native mode.

I received the following error on Exchange 2000 Server running in native mode when I tried to configure the Connection Agreement in ADC:
“Unable to contact the Exchange server, please ensure that your connections are configured correctly. ID no: c103aa1d”
How can I change the LDAP port number?
Note: I do have the exchange system administrator (xchg 5.5)in my environment.