Licensing for two domain servers

Hello all,

I have (so far) one Windows Server 2012 R2 Foundation acting as a domain controller. We are planning on adding second DC (within same domain/tree/forest) as a redundant server. Servers are used only for direct access within LAN (same subnet/VLAN, no terminal, no Hyper-V). Will number of CALs add up (to 30 CALs) or do I still have only 15 CALs ?

Thanks in advance for Your response.

Regards