Windows Server 2008 : Using dnscmd - Clearing the DNS Cache, Working with DNS Partitions

7/7/2013 9:00:33 PM

1. Clearing the DNS Cache

When a DNS server queries a forwarder, it keeps the result in the DNS cache for the time to live (TTL) specified in the DNS record. You can use dnscmd to clear this DNS cache.

Clear Cache Commands	Comments
Clear the DNS server cache. /clearcache dnscmd server /clearcache c:\>dnscmd /clearcache c:\>dnscmd dc1 /clearcache	If executed without a server name, it clears the DNS cache on the current server (assuming it’s a DNS server). You can also specify a remote DNS server for the command. Figure 5-2 shows how this is done from the DNS console.
Clear the host cache. c:\>ipconfig /flushdns	You can clear the host cache on any computer using the ipconfig /flushdns command. Note Although you can clear the host’s cache using the ipconfig /flushdns command on any computer, this is not the same as clearing the cache with the dnscmd or in the DNS console.

Figure 1. Clearing the DNS cache from the DNS console

2. Working with DNS Partitions

You might want to replicate data only between specific domain controllers. You can do this by creating directory partitions and having DNS servers enlist the partitions.

DNS Partition Commands	Comments
Create a DNS application partition. /createdirectorypartition dnscmd server /createdirectorypartition partitionFQDN c:\>dnscmd dc1 /createdirectorypartition pcgpartition.pearson.pub	Data in the partition is replicated as part of Active Directory replication, and any severs that are configured with the partition. Tip A primary purpose of creating a directory partition is to control replication between a specific group of domain controllers (DC). Figure 5-3 shows how the created partition can be picked and how an ADI DNS zone can be configured to replicate with the partition.
List directory partitions. /enumdirectorypartitions dnscmd server /enumdirectorypartitions c:\>dnscmd dc1 /enumdirectorypartitions	This lists directory partitions for the specified server. By default, there are two partitions: DomainDnsZones and ForestDnsZones. This command also lists any partitions created with the /createdirectorypartition command.
Add a partition to a DNS server. /enlistdirectorypartition dnscmd server /enlistdirectorypartition FQDNofPartition c:\>dnscmd dc1 /enlistdirectorypartition pcgpartition.pearson.pub	Adds a DNS server to the replication set of the specified partition. Note This command is not needed on the DNS server where the directory partition was created.
Remove a directory partition. /deletedirectorypartition dnscmd server /deletedirectorypartition FQDNofPartition c:\>dnscmd dc1 /deletedirectorypartition pcgpartition.pearson.pub	Deletes an existing DNS application directory partition from the specified DNS server. If this is the last server where it exists, the partition is permanently deleted.