6.3.2.4 Non-SRV Records

In addition to SRV records, a DC also registers CNAME [RFC1034] and type A [RFC1034] DNS records.

A CNAME record acts as an alias for a DNS hostname and has the following form:

• Name TTL class type RDATA

A client queries for these records by sending a DNS A, CNAME, or * query [RFC1034] to a DNS server.

If a server is a DC in forest Z, and its DSA GUID is G, then the server registers a CNAME record with Name field set to G._msdcs.Z. This name is called the DC's GUID-based DNS name.

Example: If a DC is in forest:

 Z = fabrikam.com

and its DSA GUID is:

 G = 52f6c43b-99ec-4040-a2b0-e9ebf2ec02b8

then it registers a CNAME record with:

 Name =
     52f6c43b-99ec-4040-a2b0-e9ebf2ec02b8._msdcs.fabrikam.com

The following table describes the other fields of each CNAME record registered by a server.

Field	Value
TTL	Set to dc.dnsRegistrationSettings.DNSRecordTTL.
Class	Set to IN.
Type	Set to CNAME.
RDATA	Set to the fully qualified DNS name of the server.

A type A record associates an IP address with a name and takes the form:

• Name TTL class type RDATA

A client queries for these records by sending a DNS A or * query [RFC1034] to a DNS server.

If a server is a DC with default NC X in forest Z, then it publishes a type A record with Name field X. If the DC is a GC server, it also publishes a type A record with Name field gc._msdcs.Z.

Example: If a DC has default NC:

 X = na.fabrikam.com 

and is in forest:

 Z = fabrikam.com

then it registers a type A record with:

 Name = na.fabrikam.com 

If the DC is a GC server, it registers a type A record with:

 Name = gc._msdcs.fabrikam.com

The following table describes the other fields of each type A record registered by a server.

Field	Value
TTL	Set to dc.dnsRegistrationSettings.DNSRecordTTL.
Class	Set to IN.
Type	Set to A.
RDATA	Set to the IP address of the server used for DC functions.