Network interface names

Red Hat Enterprise Linux 9.2 LPAR mode z/VM guest KVM guest

RoCE devices on Red Hat® Enterprise Linux® 9.2 use the network interface naming described here.

Network interface names for RoCE devices can be based on the devices' user-defined identifiers (UIDs) or on their function IDs (FIDs). Which of the two naming schemes is used depends on whether UID uniqueness checking is enabled for your environment.

Read the uid_is_unique attribute for any PCIe device that is available to your Linux instance to find out which naming scheme applies.

Example: 
# cat /sys/bus/pci/devices/0000:00:00.0/uid_is_unique
1

If the value is 1, UID uniqueness checking is enabled, and the network interface names are based on UIDs. For any other value, UID uniqueness checking is not enabled, and the network interface names are based on FIDs.

Network interface names based on UIDs

For Linux in LPAR mode, UIDs are specified in the PCIe device definition for RoCE adapters in the hardware configuration (IOCDS). UIDs are available only if supported by the hardware and if the LPAR is enabled for UID uniqueness checking.

UIDs are always checked for uniqueness in the following environments:
  • For Linux on LinuxONE in DPM mode.
  • For Linux on IBM® Z as a KVM guest.
  • For Linux as a z/VM® guest.
  • For Linux in LPAR mode, if the LPAR is in DPM mode.

For Linux in classical LPAR mode, UID uniqueness checking must be enabled through an LPAR setting in the IOCDS. With UID uniqueness checking enabled, UIDs are generated for any RoCE adapters for which none are assigned explicitly.

UIDs need not be unique across LPARs. For example, you can deliberately assign the same UID for the same physical RoCE device to simplify migrations between the LPARs. You can also assign the same UID to RoCE devices that connect to a specific physical or virtual LAN from different LPARs.

UID-based network interface names are of the form eno<decimal_uid>, where <decimal_uid> is the decimal representation of the hexadecimal UID. For example, for a RoCE device with UID 0010, the interface name is eno16.

Interface names based on function IDs

FIDs are associated with the slots at which RoCE adapters are plugged. Depending on your environment, you can specify FIDs in the IOCDs or they are generated for you. In contrast to UIDs, FIDs are unique across LPARs on the same IBM Z or LinuxONE hardware.

FID-based network interface names are of the form ens<decimal_fid>, where <decimal_fid> is the decimal representation of the hexadecimal FID. For example, for a RoCE device with FID 001A, the interface name is ens26.