New in Red Hat Enterprise Linux 7 / CENTOS 7 – Network Device Changes

Red Hat Enterprise Linux 7 (RHEL / RHEL 7 / RHEL7) and CentOS 7 have quite a few changes in store for those used to the way things have been done for a very long time in the Fedora/CentOS/RHEL Linux world.  Note, except where otherwise stated, information related to RHEL7 in this article applies more or less directly to CentOS7 as well.

Issue #1. Ethernet Devices are not auto-started after Install

The biggest initial shock to the system is that RHEL7 treats wired network devices a lot more like Wireless networks have been traditionally used.  By default, it won’t auto-start the devices after install, which is very much antagonistic to the “Principle of Least Surprise” way it has been done.

Issue #2. Ethernet devices don’t use “eth0″..”ethX” naming by default

This change is coupled with an effort to provide a more-consistent device naming for network devices under RHEL7.  This means that, by default, you won’t see an “eth0” in RHEL7.  Instead, you’ll see device-names like (in the case of VMWware ESXi 5.x):  “ens192”. 

Issue #3. The command-line utilities used to configure the network have changed

Oh, and they also removed ‘ifconfig’ from the default ‘Minimal Install’ of the OS.  This can make for a pretty jarring experience all-tolled.

Here are a list of things that can be done with regard to those issues:

To fix Issue #1:

During install, When the “Installation Summary” screen appears:

  1. Click on the “Network & HostName” section.
  2. The “Network & HostName” section screen will appear.
  3. Verify that an Ethernet device shows on the left column.
  4. Chick the Ethernet device in the left column to highlight it for Configuration.
  5. Click/Verify that the “ON|OFF” indicator in the upper righthand corner is “ON”
  6. Click the “Configure…” button in the lower righthand corner of the screen.
  7. The “Editing <devicename>” dialog will appear.
  8. Click on the “General” Tab.
  9. Select “Automatically connect to this network when it is available”
  10. Click the “Save…” button to return to the “Network & HostName” screen.
  11. (Optionally) Set the Hostname with a Fully-Qualified Domain Name.
  12. Click “Done” to return to the “Installation Summary” Hub screen.

To fix Issue #2:

  1. Here is the RHEL documentation concerning the consistent device naming feature
  2. If you want to suppress the consistent network device naming feature, a kernel boot parameter can now be used: net.ifnames=0
  3. Otherwise, just get used to the naming, which isn’t actually terrible, in that it uniquely identifies devices by slot number, etc (at least in the PCI,PCIe case) or by built-in numbering (Dell PowerEdge servers, etc).
  4. Note, this causes the network scripts to have names like:
    /etc/sysconfig/network-scripts/ifcfg-ens192

To fix Issue #3:

  1. Here is a link to the RHEL knowledgebase article on this issue.
  2. If you want to go back to the ‘deprecated’ ifconfig util, you can install the net-tools package by executing: yum install net-tools
  3. Alternately, the “ip” tool can be used (per knowledgebase example text below):
    # ip addr show
    # ip link show
    # ip addr add 10.10.0.123 dev eth1
    # ip link set eth1 up
    # ip link set eth1 down
    # ip route show

 

 

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