SAP Note 21151 - Multiple Network adapters in SAP Servers

Symptom:

• Installation of a new SAP system on computers with more than one network interface.

• Communication problems between the SAP servers (Application Servers, Message Server, database server).

• Some functions showing the status of the SAP installation do not work properly (e.g. transaction SM51).

• Activation of SAPHTTP or SAPFTP on the frontend may fail.

• The SAP message server will distribute hostnames that are not accessible by the clients (e.g. saplogon and SAP Web Dispatcher)
  

Other terms

Network, Interface, Adapter, TCP/IP, Routing, Route, Installation, Application Server, Message Server, Database Server, Multihomed

Reason and Prerequisites

If your SAP servers are equipped with multiple network adapters it is important to configure the TCP/IP settings according to the requirements imposed by the SAP system. Otherwise some functions of the SAP system may fail.

Solution

SAP strongly recommends that you configure the SAP server computers according to the following rules:

1. Every SAP server must have a network interface that can be reached by all Application Servers of the same SAP system and by all frontend computers and other communication partners. This can always be achieved by appropriate IP configuration.

2. The hostname of an SAP Application Server (i.e. the output of the command "hostname") must be assigned to the IP address of the network interface in item 1).

Restrictions on the hostname, mechanisms for the assignement between hostnames and IP addresses (e.g. hosts file, DNS) and exceptions that apply to high availability configurations are discussed in the "Network Guide" described below and in related notes.
The profile parameter SAPLOCALHOST may be used to make the SAP system believe it runs on a different hostname.

3. The SAP system and all frontend access and communication interfaces have to be configured using only the hostnames of item 2) or the IP address of item 1). No other IP name or IP address of an SAP server may appear in any table or configuration file of the SAP system. This rule ensures that every communication partner can actually reach the IP address that the hostname resolves into.

4. If the SAP servers are connected via a seperate fast server network, static IP routes have to be used to route the server-internal network traffic over this network.

Attention: Do not use static routes inside a Microsoft Cluster (MSCS). It may happen that after a failover a static route points to local devices, this configuration leads to connection problems on Windows.

5. The Document "Network Integration of SAP Servers" describes the TCP/IP network configuration for SAP Servers in detail. Please find this document attached to this note.