Dns On Windows Server 1002003 [Electronic resources] نسخه متنی

14.5 Resource Record Classes

Resource records
are
the basic unit of information in DNS. A name
server's primary job is to respond to queries for
resource records. Most people don't realize they are
generating queries for resource records with nearly every
network-based operation they do, including accessing a web site,
pinging a host, or logging into Active Directory.

The WMI DNS Provider fully supports querying and manipulating
resource records. Tables Table 14-5 and Table 14-6 list the supported properties and methods for
the MicrosoftDNS_ResourceRecord class, which
implements a generic interface for resource records.

www.movie.edu. 1800 IN CNAME www1.movie.edu.

The MicrosoftDNS_ResourceRecord class by itself is
not enough. There are over two dozen types of resource records, and
many have additional fields that don't have
corresponding methods in the generic interface. To solve this
problem, subclasses of MicrosoftDNS_ResourceRecord
were created for each supported record type. Each subclass provides
specific methods to access any field supported by the resource record
type. Each supported resource record has a subclass with a name in
the format of
MicrosoftDNS_RRTypeType
where RRType is the name of the record
type, such as SRV, A, or PTR.

14.5.1 Finding Resource Records in a Zone

With the marriage of DNS and


WMI,
sending DNS queries has never been so easy. By using WQL, you can
write complex query routines that would not have been possible
previously. To list all of the resource records on a server, you
simply need to execute the WQL query select * from
MicrosoftDNS_ResourceRecord against
the target server. The following example shows how to run the query
against the local name server:

set objDNS = GetObject("winMgmts:root\MicrosoftDNS")
set objRR = objDNS.ExecQuery("Select * from MicrosoftDNS_ResourceRecord")
for Each objInst in objRR
WScript.Echo objInst.TextRepresentation
next

The TextRepresentation
method is available to all resource record types since
it's defined in
MicrosoftDNS_ResourceRecord. It returns a text
string representing the resource record, such as the following:

www.movie.edu. IN  A  192.10.4.5

If you want to limit the query to only a specific zone, change the
WQL query to include criteria for ContainerName,
such as the following:

Select * from MicrosoftDNS_ResourceRecord 
Where ContainerName = 'ZoneName'

Since Active Directory stores all of the global catalog servers for a
forest and domain controllers for a domain in DNS, you can write
scripts to access this information and integrate it into your
applications. The following example does exactly this by selecting
all SRV records with a particular OwnerName. To
find all global catalog servers in a forest, you can look up
_ldap._tcp.gc._msdcs.ForestRootDNSName
; to find all domain controllers in a domain,
look up
_ldap._tcp.dc._msdcs.DomainDNSName.

option explicit
Dim strDomain
strDomain = "movie.edu"
Dim objDNS, objRRs, objRR
set objDNS = GetObject("winMgmts:root\MicrosoftDNS")
set objRRs = objDNS.ExecQuery("Select * from MicrosoftDNS_SRVType " & _
" Where OwnerName = '_ldap._tcp.gc._msdcs." & _ 
strDomain & "'")
WScript.Echo "Global Catalogs for " & strDomain
for Each objRR in objRRs
Wscript.Echo " " & objRR.DomainName
next
Wscript.Echo
set objRRs = objDNS.ExecQuery("Select * from MicrosoftDNS_SRVType " & _
" Where OwnerName = '_ldap._tcp.dc._msdcs." & _
strDomain & "'")  
WScript.Echo "Domain Controllers for " & strDomain
for Each objRR in objRRs
Wscript.Echo " " & objRR.DomainName
next

14.5.2 Creating Resource Records

With the DNS Provider,

creating resource records can be done
in a couple of steps. The
CreateInstanceFromTextRepresentation method takes
the following parameters: the domain name of the name server to
create the record on, the domain name of the zone to add the record
to, and the textual representation of the resource record. It also
provides an out parameter that is a
MicrosoftDNS_ResourceRecord object representing
the newly created record.

The following example goes through the process of creating both an A
and a PTR record. Both records are typically necessary when adding a
new host to DNS:

option explicit
Dim strRR, strReverseRR, strDomain, strReverseDomain
' A record to add
strRR = "matrix.movie.edu. IN A 192.168.64.13"
strDomain = "movie.edu"
' PTR record to add
strReverseRR = "13.64.168.192.in-addr.arpa IN PTR matrix.movie.edu"
strReverseDomain = "168.192.in-addr.arpa."
Dim objDNS, objRR, objDNSServer, objRR2, objOutParam
set objDNS = GetObject("winMgmts:root\MicrosoftDNS")
set objRR = objDNS.Get("MicrosoftDNS_ResourceRecord")
set objDNSServer = objDNS.Get("MicrosoftDNS_Server.Name="."")
' Create the A record
Dim strNull
strNull = objRR.CreateInstanceFromTextRepresentation( _
objDNSServer.Name, _
strDomain, _
strRR, _
objOutParam)       
set objRR2 = objDNS.Get(objOutParam)
WScript.Echo "Created Record: " & objRR2.TextRepresentation
set objOutParam = Nothing
' Create the PTR record
strNull = objRR.CreateInstanceFromTextRepresentation( _
objDNSServer.Name, _
strReverseDomain, _
strReverseRR, _
objOutParam)       
set objRR2 = objDNS.Get(objOutParam)
WScript.Echo "Created Record: " & objRR2.TextRepresentation

The WMI DNS Provider fills a much-needed gap for programmatic
management of a Microsoft DNS environment. In this chapter, we gave
an overview of WMI and covered the classes used for managing name
server and zone configuration along with the available properties and
methods. We described how to query, add, and delete resource records
with the DNS Provider and showed how you can
get a list of Active Directory domain controllers using a simple


WQL
query.