You need to manually create a service location (SRV) record for a server that has the Key Management Service (KMS) installed.

Which SRV record should you create?

A.
_kms._tcp.contoso.com

B.
_kms._tcp._msdcs.contoso.com

C.
_mskms._tcp.contoso.com

D.
_vlmcs._tcp.contoso.com

Explanation:
Manually Create SRV Records in DNS

If the environment does not support DDNS, the SRV RRs must be manually created to publish the KMS host. Environments that do not support DDNS should disable publishing on all KMS hosts to prevent event logs from collecting failed DNS publishing events. To disable auto-publishing, use the Slmgr.vbs script with the /cdns command-line option. See the “Configuring KMS” section for more information about the Slmgr.vbs script.

Note   Manually created SRV RRs can coexist with SRV RRs that KMS hosts automatically publish in other domains as long as all records are maintained to prevent conflicts.

Using DNS Manager, in the appropriate forwarding lookup zone, create a new SRV RR using the appropriate information for the location. By default, KMS listens on TCP port 1688, and the service is _VLMCS. Table 2 contains example settings for a SRV RR.

Table 2   SRV Resource Record

Source: http://technet.microsoft.com/en-us/library/ff793405.aspx