The only way to get around this would be to use a SAN cert with a generic
name as the common name and use the same certificate on both servers.
For example if your servers were:
Cppm1.domain.com
Cppm2.domain.com
Use cppm.domain.com as the common name and add the above 2 in the SAN.
Keep in mind that for RADIUS, the common name doesn't have to match the DNS
name of the server. It is just what is presented to the client.
Many universities use a generic "wireless.university.edu" as the CN so it's
easy to understand by users.