Automatic configuration of network interfaces
When a new network adapter is physically installed in the system, the operating system automatically adds the appropriate network interface for that adapter.
For example, if you install a token-ring adapter in your system,
the operating system assigns it the name tok0 and
add a token-ring network interface named tr0. If
you install an Ethernet adapter in your system, the operating system
assigns it the name ent0 and add both an Ethernet
Version 2 and an IEEE 802.3 interface, named en0 and et0 respectively.
In most cases, there is a one-to-one correspondence between adapter
names and network interface names. For example, token-ring adapter
tok0 corresponds to interface tr0,
adapter tok1 corresponds to interface tr1, and so
on. Similarly, Ethernet adapter ent0 corresponds
to interface en0 (for Ethernet Version 2) and et0 (for
IEEE 802.3), and adapter ent1 corresponds to interface
en1 (for Ethernet Version 2) and et1 (for
IEEE 802.3).
In the case of ATM, according to RFC1577, it is possible for an ATM station to be part of multiple Logical IP Subnetworks. In this case, multiple interfaces are associated with a device. This requires that an interface be specifically added and a device name be assigned to it.