When configuring a RDWA Farm, Connection broker HA or Gateway Services it is recommended that you use a SAN or Wild certificate.
SAN certificates allow you to use alternative names providing alternative name resolution for internal and external connections.
Please see the following Link http://www.cacert.org for Free certificates. I would recommend purchasing certificates for production environments.
Open MMC > add snap in > select Local computer certificates.
Right click > All Tasks > Advanced Operations > Create Custom Request
Ensure that you select Proceed without enrollment policy
Select Legacy Template Key and PKCS#10
Configure the properties.
Enter a friendly name for the certificate and a description .
Creating the Subject Name of the SAN Certificate
To create the san certificate, you would need to enter the following fields into the subject name.CN=remotedesktop.example.com OU=example company O=IT POBox= STREET=downing street STREET= STREET= L= S= PostalCode= C= Email= Phone=
Add Server Authentication to the selected options
select a Key Size of 4096 and a key type of Exchange Type
Click Next after configuring the certificate
Save the request file to a location of your chose.
You can check your CSR using the following tool https://secure.comodo.net/utilities/decodeCSR.html