Predictable network device names

LPAR mode z/VM guest KVM guest

Ubuntu Server 20.04.1 uses predictable names for network devices. These names are stable across reboots and network adapter replacements.

Predictable naming is enabled by default. In this naming scheme, a mainframe network device has a name of the following form:

<pf><type><bus_id>

For example:

encf5f0

Where:

<pf>
A two-character prefix for the network type. The type can be one of the following:
  • en - Ethernet
  • ww - WAN
  • sl - serial line
<type>
The device type. The device type of channel command word (CCW) devices is c. For PCIe devices, the type is s.
<bus_id>
The bus ID identifies the device within the scope of a Linux instance. For a CCW device on Ubuntu, bus IDs can take different forms, depending on the subchannel set through which the device is accessed. For subchannel set 0, the bus ID is the device number with stripped leading zeroes. For all other subchannel sets, the bus ID is the subchannel set ID followed by a dot, followed by the 4-digit device number.

Examples:

  • Device number 0009 on subchannel set 0 has the bus ID 9
  • Device number 0b41 on subchannel set 2 has the bus ID 2.0b41

You can use lszdev or lscss -a to obtain a list of the network devices in your system.