When using a custom DNS name, you will not be able to browse to the Enterprise BI Portal on the local server unless you add the DNS name to the registry. Follow the below steps to do so;
Open regedit.exe from Start Menu > Run.
Browse to HKEY_LOCAL_MACHINE > SYSTEM > CurrentControlSet > Control > LSA > MSV1_0.
Right click MSV1_0 and select New > Multi-String Value.
Name the key BackConnectionHostNames.
Edit the string by double clicking on it.
Enter the DNS name for use with the BI Portal here.
If the key already exists, just append the DNS name on a new line.
Restart the Server for changes to take effect.