SAP Basis Tech Supports

Symptom

If you use DHCP in Windows Server 2008 Failover Clustering, you obtain duplicate DNS entries that have the same IP-Address for two different host names.
This applies to all Windows Server 2008 versions with SP1 and SP2.

Other terms

MSCS, Windows Server 2008 Failover Clustering, Failover Cluster, DNS resolution, duplicate host name entries

Reason and Prerequisites

With Windows Server 2008 Failover Clustering, Microsoft supports DHCP on the network adapters that are used on MSCS nodes.
In the following, we assume that we have 2 cluster nodes each of them having one network adapter. The network adapters use DHCP-configured IP addresses.
Situationbeforecreating a Windows Failover Cluster on the cluster nodes:
When checking the network configuration with nslookup , you get the following IP addresses:
NodeA: 10.10.1.100
NodeB: 10.10.1.101
When checking the resolution of IP addresses to host names (ipconfig -4 -a ), you get the correct host name for the specified IP address.
Situationaftercreating a Windows Failover Cluster on Node A (DHCP assigned IP address 10.10.1.110 to the cluster network name ClusterA):
When checking the network configuration nslookup , you get the following IP addresses:
NodeA: 10.10.1.110 (!)
NodeB: 10.10.1.101
ClusterA: 10.10.1.110
When moving the cluster group to NodeB with cluster.exe (there is no GUI option for this function in the Failover Cluster Administrator), and you check the network configuration with nslookup , you get the following IP addresses:
NodeA The IP address cannot be resolved
NodeB 10.10.1.110 (!)
ClusterA 10.10.1.110
When moving the cluster group back to NodeA, and rechecking the network configuration with nslookup , the DNS entries look like these:
NodeA 10.10.1.110 (!)
NodeB The IP address cannot be resolved
ClusterA: 10.10.1.110
However, correct would be in all cases:
NodeA 10.10.1.100
NodeB 10.10.1.101
ClusterA 10.10.1.110

Solution

To avoid these duplicate DNS entries, you have the following options:
You do not use DHCP on Windows Server 2008 Failover ClustersIf you use DHCP, you have to change the private property PublishPTRRecords=1 to any cluster resource of resource type “Network Name”.
To do this, perform the following steps:a) Since, this property is not visible in the Property Dialog of the Failover Cluster Administrator, open a command box “as administrator”.b) Run the following command:
cluster res “resource name” /priv PublishPTRRecords=1c) Set this property for all “network name” resources.d) Bring the network name resources offline and online again to activate the changes.e) Renew the IP addresses of the network interfaces and force a reregistration of the IP addresses in DNS with the following command:
ipconfig /allf) Repeat steps a, b, d, and e, every time and for every new resource of resource type “network name” that you create.g) In addition, run ipconfig /all every time after you have rebooted the server.
We recommend creating a script and scheduling it with the Windows Task scheduler to run after every system start.