Consistent network interface names and LCFG

As explained in an earlier post, we are moving to the more “modern” consistent network interface naming scheme because the old-style method of hard-wiring interfaces to interface names of the form eth0 no longer works with RHEL7. This is a problem for machines with multiple interfaces – eg servers.

(Note that you can stick with the legacy naming scheme by defining LCFG_NETWORK_LEGACY_NAMING at the head of a machine’s profile).

As a recap, under the consistent naming scheme, interfaces are known as :-

Device Name
On-board (embedded) interface em[1234…]
PCI card interface p<slot>p<port>
Virtual p<slot>p<port>_<virtualif>

For example, a minimally configured Dell R730 has four on-board interfaces : these would be called em1, em2, em3 and em4.

We could modify all our LCFG configuration to use the new names directly. However, there are many LCFG macros which assume that network interfaces are of form eth[n] and changing these would be somewhat disruptive. We have decided to stick with using the old form eth[n] in LCFG configuration, providing a means of associating these names with a real physical device. The macro call LCFG_NETWORK_SET_DEVICE(eth0,em1)  will associate the LCFG name eth0 with the physical device em1.  The hardware headers for each machine model will include calls to LCFG_NETWORK_SET_DEVICE for all the onboard network interfaces. This means that the process should be largely transparent on most machines.

Some machines have both embedded and PCI-E interfaces. For example, in Informatics, HP DL180s will commonly have two onboard interfaces and one PCI-E interface. We usually configure these machines such that a network bond is formed using one of the onboard interfaces (usually the second as the first is used for IPMI) and the PCI-E interface. On DICE, the following will be configured by default for these machines :-


Note that old form of eth[n] is only used in LCFG configuration – all operating system tools (eg netstat) and configuration will expect names of the form em[n] or pp.

We shall probably convert LCFG configuration to use the native network interface names throughout – possibly at the next major platform upgrade.

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