SAP Basis Tech Supports

Symptom
You want to use one or more virtual host names for SAP software within an SAP server landscape to hide the physical network identities for the pieces of software from each other.
This may be useful when moving SAP servers or complete server landscapes to other new hardware within a short time frame without having to carry out a reinstallation or complicated reconfiguration. This procedure is also used in failover cluster solutions, for example.
Other terms
Virtualization, failover cluster, system copy, system cloning, DMZ
Reason and Prerequisites
You require a new IP address for each virtual host name. The steps described below apply only to SAP server software based on SAP NetWeaver.
Solution
To decouple the SAP servers securely and permanently from their physical network identities (TCP host name + IP address), you require a new network identity. If required, you can move this with the SAP server software and its configuration to new hardware. This new network identity must consist of a new host name AND a new IP address in order to complete the decoupling from the physical server.
We recommend that you avoid using TCP alias names within a server infrastructure (see below). Since this new network identity will no longer be bound to the physical hardware, it is referred to as a “virtual” network identity.
Caution: The corresponding steps of this procedure that are required for Microsoft Windows are described in detail by Note 1282975.

Procedure:
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1. Set up a new IP address on the SAP server. In general, this can be done via ifconfig (Unix).2. On UNIX, additional IP addresses for network adapters are addressed for the adapter, for example, via eth0:1 or lan0:1. For more details, refer to the ifconfig Manual Pages.3. Register a new host name for the IP address in the DNS servers or in the /etc/hosts file
Example:
<ip1> physhost.domain. corp physhost
<ip2> virthost1.domain. corp virthost
If you only use the hostst file, you must enter the information on all servers that are to use the new virtual host.4. Next, install or configure your SAP server using the new “virtual” network identity. Information is available in the installation guides at http://service.sap.com/instguides.
To ensure that SAP processes use one of these alternative network identities within an SAP instance, you must include the following profile parameters in the start and instance profile of the relevant instance (the installation already does this if you use the SAPinst option SAPINST_USE_HOSTNAME to install the server).
SAPLOCALHOST = <virtual host name>
SAPLOCALHOSTFULL = < full qualified virtual host name>
All SAP processes within the SAP instance that require SAP profiles to start will then use the virtual network identity for future communication.

Additional information:
Do not use any TCP network alias names to virtualize physical host names within the intra-server communication. This is due to the host name and IP address resolution that is sometimes executed repeatedly by server applications, and which usually results in the actual physical host name instead of the virtual name. Refer to Note 129997.
However, network aliases can normally be used to decouple end-user communication from the physical server infrastructure (for example, aliases for connections between a user and an ABAP application server via HTTP WebServer or SAP GUI).