This article shows you how to update LDAP credentials on the Netscaler VPX 1000. It goes over logging in, editing virtual server, and applying settings.
Login to the NetScaler Device
Default User: nsroot Pass: nsroot (or password you changed it to)
Go to Netscaler gateway virtual server controlling your logins
Click on LDAP Policy and select Edit Server
Update the credentials under connection settings, and also test the new settings.