You will get the following error while first time configuring BCS.
Message from External System: ‘Login failed for user ‘NT AUTHORITY\ANONYMOUS LOGON’.’.
Following would be the solution.
Open SharePoint Designer. Go to External Content Types > Open BCS item > Click Connection Properties button.
Choose the Authentication Mode as BDC Identity as shown below.
Save changes & Retry opening your BCS List.
In this post we have explored a common error while configuring BCS & steps to resolve it.