Use the predictable network interfaces’ names

There is the launchpad blueprint about the spec.

Allow arbitrary names for network interfaces in Fuel. The practical reason is to fix known issues for classical naming policy by using the predictable interface naming policy.

Problem description

Currently Fuel relies on an old-fashioned (classical) ethX network interfaces naming. Such a naming is known to be unstable in the following ways:

  1. two machines with the same hardware can have different interface naming, consider two machines having an on board NIC and the one installed into PCI-E slot. Depending on luck the name of the interface corresponding to the on-board NIC can be eth0 on machine 1, and eth1 on machine 2.
  2. the interfaces’ names are not preserved across the reboots.

Switching to predictable interface naming policy doesn’t require creating extra udev rules pinning (classical ethX) interface name to the corresponding MAC address to hold the same interface name after a reboot.

The 2nd problem can be solved by udev rule which pins the interface name to the MAC address of the NIC. Solving the 1st problem requires a different naming convention, such as the predictable network interfaces’ names (as implemented in udev >= 197). Modern Linux distributions (Ubuntu >= 15.04, CentOS >= 7) use this scheme by default, and it can be enabled in Ubuntu 14.04 (and Debian Jessie).

Hard-coded interface names ethX in Fuel code should be changed to support arbitrary interface naming schemes.

By default, contemporary systems name Ethernet interfaces using different from the conventional policy and can apply one of supported naming schemes.

Example of classical interface naming, the interfaces are named as “eth0”, “eth1”:

$ ip -4 link
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP
   mode DEFAULT qlen 1000 link/ether 00:50:56:9c:74:4d brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP
   mode DEFAULT qlen 1000 link/ether 00:50:56:9c:03:0a brd ff:ff:ff:ff:ff:ff

Example of interface naming based on physical location of the hardware (PCI bus). The interfaces are named as “enp0s3” , “enp0s8”:

$ ip -o -4 link
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
      state UP mode DEFAULT qlen 1000
      link/ether 08:00:27:4b:f0:40 brd ff:ff:ff:ff:ff:ff
3: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
      state UP mode DEFAULT qlen 1000
      link/ether 08:00:27:bc:4d:85 brd ff:ff:ff:ff:ff:ff

Example of interface naming based on MAC addresses. The interfaces are named as “enx0800274bf040” and “enx080027bc4d85”:

$ ip -o -4 link
2: enx0800274bf040: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
      qdisc pfifo_fast state UP mode DEFAULT qlen 1000
      link/ether 08:00:27:4b:f0:40 brd ff:ff:ff:ff:ff:ff
3: enx080027bc4d85: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
      qdisc pfifo_fast state UP mode DEFAULT qlen 1000
      link/ether 08:00:27:bc:4d:85 brd ff:ff:ff:ff:ff:ff

Ethernet interfaces could also have names incorporating Firmware/BIOS provided index numbers for on-board devices (example: eno1), names incorporating Firmware/BIOS provided PCI Express hotplug slot index numbers (example: ens1).

Proposed changes

Fuel (master nodes, slaves, bootstraps, etc) shall support the predictable interfaces’ names and use it by default. Hard-coded interface names and regular expressions bounded to a particular naming policy shall be avoided in the code.

Here are examples from the code (written in bash), which should be re-worked. The “eth0”, “eth1” and “eth.” should be changed in the code below:

ALL_ETH_IP=$(ip -o -4 addr | grep "eth." | awk '{print \$4 }' | cut -d/ -f1)

There are default settings (expectations) in Fuel. For example, the interface eth0 is expected to be an admin interface by default now.

Since Ethernet interfaces could have any names (we can’t predict which one it would be), and to preserve backward compatibility with the current classical naming schema (ethX), the following approach is proposed for changes in code:

  1. List of physical Ethernet interfaces should be collected from the system.
  2. This list is sorted in alphabetic order.
  3. The very first interface from the sorted list is assigned to the role of eth0, the second interface is assigned to the role of eth1 , etc ...

The function gathering Ethernet network interface names is required to implement the feature. The function should collect information about only physical Ethernet interfaces in the system (avoid virtual, e.g. loopback, tunnel, VLAN, bound interfaces ... etc and wireless).

Web UI

The feature doesn’t require changing the web UI, the possible impact is a variable size for an interface names placeholder.


The code related to the processing network interface names should be changed to get rid using templates sticked to a particular interface naming schemes like “eth*”. The code of Nailgun doesn’t require such changes, but Nailgun agent’s code should be improved. There is the bug reported on nailgun-agent.

Interfaces’ names are kept as metadata of clusters and nodes in the database. Nailgun shall collect information from Nailgun agent on slaves about interface names and detect the renaming and update (if it has not been implemented) the names in the database using the MAC addresses to stick to.

Data model






RPC Protocol


Fuel Client



Plugins are ofter made by third-party teams. The code should be written in a way avoiding stick to a particular interface naming schema.

Fuel Library

Fuel Library is abstract enough to be interface name agnostic. We use bridges with names like ‘br-mgmt’ and this is matter of Nailgun to decide which port to put into which bridge. The only problem here is to retain interface mapping on-bootstrap/installation/post-installation phases which is a matter of fuel-agent and Nailgun teams. Fuel Library is not affected by interface naming unless there is some bug. We are using custom bridges names which attach corresponding physical interfaces according to the info sent in network_scheme which is currently generated by Nailgun. So far, there is no Library impact for this feature.


We can stick to the classicall interface naming schema, but it does not allow us to work with contemporary Linux distributions using another network interface naming policies and prevent from including already deployed hosts (like RHEL) to Fuel environments.

Upgrade impact

Upgrading from CentOS 6.x to CentOS 7.0 lead to change network interface naming policy and can break a network configuration used before the upgrade.

The interfaces’ names from slave nodes are kept as metadata in configs. The additional step to match and update the new names in configs shall be introduced during updgrade before the configs will be applied. The plausible solution is to stick to hardware (MAC) addresses, when the naming of network interfaces are changed. The (upgrade) scripts should collect information about current network configuration and modify the configs in way preserving current interfaces’ roles.

It’s possible to caught the case after an upgrade when the IBP images have been built for classical interface naming schema, but bootstrap image uses predictable interface naming policy. Since the software has a flaw, which doesn’t allow updated interfaces’ names between provisioning and deployment phases (in manifests), the document how to either rebuild IBP images or suppress predictable interface naming policy on the bootstrap should be provided for a customer. (The flaw is going to be fixed in the nearest releases.)

Security impact


Notifications impact


End user impact

The user should be careful when assigning interface roles of several nodes at once. Just because two nodes have the interface called enp2s0f0 doesn’t mean both these interfaces are attached to the same L2 network (unless the nodes’ hardware is the same).

Since the interfaces’ names could be changed during upgrade, the user should review the config files from the slave nodes to match new interfaces’ names with the old one.

Performance impact


Deployment impact


Switching to predictable interface naming may change interfaces’ names during deploying or upgrading a cluster. Potentially it is possible, that an interface on a slave node get the name (during provisioning) differ from the name it has previously taken on bootstrap. For example, if the bootstrap is based on a differ OS, than OS using on provisioning (the boostrap is based on CentOS, but Ubuntu is to be provisioned later and both using different naming policies). But it doesn’t impact on deployment if Nailgun agent passes to Nailgun correct interface names, which shall be updated in the database before the serialization the data has started.

Developer impact

The approach of using templates (like “eth*”) for collecting information about (physical) interface names should be avoided, because any network naming policy could be used. The corresponding function returning list of (physical) network interfaces should be implemented. It would be better to stick to MAC addresses of network interfaces instead of interface names.

Infrastructure impact

Impact on fuel-devops

Please keep in mind, that achive predictable interface names two parameters biosdevname=1 and net.ifnames=1 should be passed to the kernel on boot. The next obligitory requirement (in case of deploying on VMs) is chose network driver E1000, but not VMXNET2 or VMXNET3, using by default in most cases.

The main impact is to create interfaces in predictable way. Currently we create interfaces based on infomation from fuel-devops/devops/, lines are like:

DEFAULT_INTERFACE_ORDER = 'admin,public,management,private,storage'
'admin': ['eth0', 'eth1']

There is a work in fuel-qa/fuel-devops template-based-testcases to move that to yaml files with settings, so it is going to be fixed anyway. Later changes will require simple rename in yaml files.

Interface order is used to correctly create interfaces in virtual domains. Currently INTERFACE_ORDER is primary source of truth. Based on that ordering we map networks to interfaces.

def create_interfaces(self, networks, node,
    interfaces = settings.INTERFACE_ORDER
    if settings.MULTIPLE_NETWORKS:'Multiple cluster networks feature is enabled!')
    if settings.BONDING:
        interfaces = settings.BONDING_INTERFACES.keys()

Also, IPMI driver is slightly affected:

class DevopsDriver(object):
    def _create_boot_menu(self, interface='eth0', ...

And node model. It is enough to rename eth0 to correctly mapped the first interface:

def pxe_boot_interface_is_eth0(self):
def interfaces(self):
    return self.interface_set.order_by('id')

Impact on fuel-qa

The main impact in fuel-qa is a communication with the nailgun. With current nailgun scheme we need just to change interface information updates in fuel-qa/fuelweb_test/models/ There are 14 lines to send to nailgun interfaces. Need to carefully update them with information from yaml files and devops. For now we need to update info based on INTERFACE_ORDER and test logic.

Simple fix in tests of fuel contrail plugini in fuel-qa repository:

raw_data = [{
           'mac': None,
           'mode': 'balance-rr',
           'name': 'bond0',
           'slaves': [
               {'name': 'eth4'},
               {'name': 'eth2'},

Also, simple fix in dhcrelay_check:

def dhcrelay_check(self):
   with self.d_env.get_admin_remote() as admin_remote:
       out = admin_remote.execute("dhcpcheck discover "
                               "--ifaces eth0 "

Simple replace of ‘eth*’ in currently used network templates, see:


This is a folder with yaml files which are going to be base for tests. Same as above - replace ‘eth*’ is enough.

Documentation impact

Switching to predictable network interfaces’ names may require some changes in documentation. Diagrams and User Guide should be reviewed to support new network schemes.

Expected OSCI impact




Primary assignee:
Albert Syriy <>
Other contributors:
Ivan Suzdal <> Alexei Sheplyakov <> Alexandr Kostrikov <> Alexey Shtokolov <>
Mandatory design review:
Aleksandr Gordeev <> Igor Kalnitsky <> Sergii Golovatiuk <> Sergey Vasilenko <> Vladimir Kozhukalov <> Vladimir Kuklin <>

Work Items

The following parts of the project require improving:

* Nailgun
* Fuel-main
* Fuelmenu (LP#1512479)
* Fuel-QA tests
* Fuel scale tests



Testing, QA

We are having impact on two subsystems: fuel-devops and fuel-qa. Jenkins jobs are not affected.

Acceptance criteria

Fuel should work well with different Ethernet interface naming policy. In general Ethernet interface can have an arbitrary name.