"The namespace cannot be queried. The RPC server is unavailable." error attempting to create a DFS namespace on Windows Server 2008


Symptoms


You may receive the following error when attempting to create a DFS namespace on a Windows Server 2008 computer:

The namespace cannot be queried. The RPC server is unavailable.

This issue is typically seen in an environment using a third-party DNS server.

Cause


This error can occur when no DomainDNSName records are registered for the domain. These records are updated by the Netlogon service on domain controllers. These are the "same as parent" A records in domain's forward lookup zone.

The following documentation indicates these records are not a requirement and are only used for DNS clients that do not understand SRV records.

How DNS Support for Active Directory Works
http://technet.microsoft.com/en-us/library/cc759550(WS.10).aspx:

DnsDomainName

Enables a non-SRV-aware client to locate any domain controller in the domain by looking up an A record. A name in this form is returned to the LDAP client through an LDAP referral. A non-SRV-aware client looks up the name; an SRV-aware client looks up the appropriate SRV resource record.

In a network trace you will see a DNS lookup for the DomainDNSname A record and the DNS server will respond with the SOA record if these A records do not exist.

DNS lookup query: 

Dns: QueryId = 0x887C, QUERY (Standard query), Query  for adatum.com of type Host Addr on class Internet
QRecord: adatum.com of type Host Addr on class Internet

Response with the SOA record:

Dns: QueryId = 0x887C, QUERY (Standard query), Response – Success
QRecord: adatum.com of type Host Addr on class Internet
AuthorityRecord: adatum.com of type SOA on class Internet: PrimaryNameServer: adadc1.adatum.com, AuthoritativeMailbox: hostmaster.adatum.com

Resolution


Update the A records on the DNS server, or create a HOSTS file on the Windows Server 2008 computer that includes the fully qualified name and the IP addresses of the domain controller.

Sample HOSTS file:

adatum.com      192.168.2.10
adatum.com      192.168.3.10
adatum.com      192.168.4.10