With Server 2008 Failover Cluster service it is possible to use DHCP to assign the cluster IP address when the Failover Cluster is created.
Depending on how the DHCP Server is set up with regards to registration of DNS A and PTR records, you may end up with a DNS PTR record for the IP address of the cluster that has the name of the active node of the failover cluster rather then the alias name of the Failover Cluster. This can cause issues for programs that use the DNS PTR records to confirm the IP Address to Name pair of the Failover Cluster.
This issue will occur when in the DNS tab of the DHCP server or scope properties the option “Enable DNS dynamic updates according to the settings below:” is checked and the option “Always dynamically update DNS A and PTR records” is selected.
With these settings, when the Failover Cluster service brings the cluster on line for the first time the DHCP client on the cluster node where the cluster is being created will request an address from the DHCP service for the cluster alias. Then the DHCP server will give out an address to the client, and register in DNS a PTR record using the newly assigned alias IP address. However, the data field will show the name of the active cluster node, not the alias name of the cluster.
When the Failover Cluster is created, the cluster service calls into the DHCP client service to have the DHCP client get an IP address for the cluster alias. The DHCP client in its request to the DHCP server for the IP address will use the name of the cluster node, not the Failover Cluster alias name. This results in the DHCP server using this cluster node name in the registration of the PTR record.
Follow the steps outlined below to create a PTR record in DNS that will contain the alias name of the Failover Cluster:
1. In the DNS management console, delete the existing DNS PTR record for the cluster alias. Refer to: http://technet.microsoft.com/en-us/library/cc759561.aspx
2. On the cluster node that is active enter the following command at a command prompt – cluster.exe /cluster:<clusteralias> res "Cluster Name" /priv PublishPTRRecords=1
3. Take the cluster offline and bring it back online so the new setting for PublishPTRRecords takes effect and the correct PTR record is registered.
Note: If for some reason the PTR record gets changed or deleted, repeat step one above and use the following command to do a manual registration of the PTR record in DNS without having to take the cluster offline/online – cluster.exe /cluster:<clusteralias> res "ClusterName" /registerdns.
One possible scenario that may cause this PTR record to be changed or deleted: if the Failover Cluster is offline long enough for the DHCP lease to expire, and the DHCP server removes the entry when it deletes the lease.
The Failover Cluster service does do an independent registration of the "A record" for the cluster alias name after the IP address has been acquired with the DHCP client. By default the PTR record is not registered, so the PublishPTRRecords property has to be set so that it is registered going forward.
Please Note: Even if the Cluster service defaulted to registering the PTR record, it may not be able to override the record registered by DHCP if aging and scavenging are enabled on the DNS server, or only secure updates are used.
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