Client side TLS certificates

I have read the Secure Calling Tutorial ( and can get it to work. When creating the certificates for client and server, you are specifying the server address in the build. So the certificate will only work on the specified server.

I was wondering if its possible to build a certificate that would be valid on multiple servers.

We have softphones that I want to register to multiple asterisk boxes and not have to install separate certificates on the client side for each Asterisk server.