The following network configuration examples show how you can set up your network for small, medium, and large R/3 Systems. All these configurations serve as examples and are not compulsory. However, if you set up different networks, you must still follow the SAP guidelines for network configuration.

For smaller R/3 Systems, the R/3 server uses only one network adapter for communicating with the SAPgui frontends. Since the network load is very low through SAPgui frontends, you do not need to connect the R/3 server using several, physically separate subnets (network adapters). Dividing up the rest of your network into subnets is possible and also useful. High data traffic only occurs locally on the R/3 server between the database and the central instance.

If your R/3 System consists of several servers, a high network load occurs between the database server and the application servers. A high-speed switch (at least 100 MBit) is suitable for a simple and cost-effective connection of the servers.

You can use one or two network adapters for each server. The differences are explained below.

The entire data traffic of a server runs over one network adapter only. Therefore, you need a network adapter with sufficient transfer speed (at least 100 MBit). If the servers connect using the switch, ensure that the entire bandwidth is available to all ports. The host name of the servers must match the IP name for the respective network adapter.

In very large R/3 Systems, the network adapter can become a bottleneck. In this case, you can install a second network adapter for each SAP server. It is only used for the communication between the R/3 servers (database server, central instance and dialog instance) (server network).

This type of configuration also lets you separate the data traffic between the application servers and the database server from the rest of the data traffic. If you need to, you can install several network adapters on the database server.

Two possible configurations are described in the following section.

If an SAP instance also runs on the database server, you must connect this host to the backbone and the server network. When you assign the host name to an adapter, the same guidelines apply as with the application servers: The host name is assigned to the backbone connection.

In this configuration, routing entries must already exist on the application servers, ensuring that the database traffic flow is actually running over the server network.

When you are deciding if you want to install an additional SAP instance on the database server, consider performance and tuning aspects.

In this configuration, all the application servers are connected to the corporate backbone and to the server network. This complete isolation of the database server has advantages and disadvantages. Being separated from the rest of the corporate network guarantees high security against unwanted access to sensitive data, and against accesses that can hurt availability and performance on this important server. In this case, an SAP instance cannot run on the database server.

If a bottleneck occurs in the network adapter that connects the database server to the server network, you can establish an another connection to the server network with an additional network adapter.

For performance reasons, do not back up the data on the server, in particular the database server, over the server network. If you need to back up the data over the network, we recommend using a separate network for the backup (SAN = Storage Area Network). In this case, the database server must be equipped with an additional network adapter to connect to the SAN.