Assigning Names to Data Links

From an administrative perspective, a network interface has a link name. The data link represents a data-link object in the second layer of the Open Systems Interconnection (OSI) model. The physical link is directly associated with a device and possesses a device name. The device name is essentially the device instance name, and is composed of the driver name and the device instance number.

Driver names can be ce, hme, bge, e1000g, among many other driver names. The variable instance-number can have a value from zero to n, depending on how many interfaces of that driver type are installed on the system.

For example, consider a 100BASE-TX Fast Ethernet card, which is often used as the primary NIC on both host systems and server systems. Some typical driver names for this NIC are eri, qfe, and hme. When used as the primary NIC, the Fast Ethernet interface has a device name such as eri0 or qfe0.

Only one interface can be configured on NICs such as eri and hme. However, many brands of NICs can have multiple interfaces. For example, the Sun Quad FastEthernet^TM (qfe) card has four interfaces, qfe0 through qfe3. See Figure P–1.

With the separation of the network configuration between the software layer and the hardware layer, you can now use flexible names for data links . The device instance name continues to be based on the underlying hardware and cannot be changed. However, the data link name is no longer similarly bound. Thus, you can change the device instance's link name to a name that is more meaningful in your network setup. You assign a customized name to the link, and then perform network configuration and maintenance tasks by referring to the assigned link name instead of the hardware-based name.

Using the information in Figure P–2, the following table illustrates the new correspondence between the hardware (NIC), the device instance, the link name, and the interface over the link.

As the table indicates, the ce0 device instance's link is assigned the name subitops0, while the link for the qfe3 instance is assigned the name subitops1. Such names allow you to readily identify links and their functions on the system. In this example, the links have been designated to service IT Operations.