Issues with NIC Detection: Centos 6 on a VM

December 30th at 12:00am

Does this ever happen to you: After provisioning a VM with Centos you discover that it has not detected the virtual NIC. It happens to me on occasion and can get annoying.

Symptoms:

  • No internet access (of course)
  • When you run ifconfig, you only see output for lo

1-No_Ethernet.png 

This article:

  • Shows how to tell if the NIC is "physically" installed correctly
  • Walks through a manual configuration scenario

Notes:

 

How to tell if the NIC is attached:

Run these 2 commands:

  • lspci | grep -i eth
  • dmesg | grep eth

You should see messages listing your NIC (Make/Model and connetion status):

lspci_output.png

 

Configure the NIC:

  • Run system-config-network and set the IP Address, Subnet and DNS settings
    3-system-config-network.png

  • Open /etc/sysconfig/network using nano / pico / vi / other text editor and setup your gateway (if you are using a Static IP Address)
    4-Add_Gateway.png

  • Edit /etc/sysconfig/network-scripts/ifcfg-eth0 and ensure ONBOOT=yes
    5-Mark_eth_as_active.png
    If you want to setup a Static IP Address include these additional entries (Sample data: replace with values appropriate to your environment):

    IPADDR=10.10.45.56
    NETMASK=255.255.255.0
    DNS1=10.10.45.1

    Change BOOTPROTO=dhcp to BOOTPROTO=static

  • Run service network restart and note that eth0 should be started:
    6-restart_networking.png

  • Validate that eth0 is up and running by by using ifconfig:
    7-Validate_eth_works.png

 

This seems to work for me- if you know a better method, let me know in the comments area. 

 

UPDATE 24-May-2012

I ran into a couple of errors that should be noted here:

Error 1:

[root@rcarter-PhantomDebugger-Centos6-x64 /]# service network restart
Shutting down interface eth0:  Error: Device 'eth0' (/org/freedesktop/NetworkManager/Devices/0) disconnecting failed: This device is not active
                                                           [FAILED]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0:  Error: Unknown connection: 5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03.
                                                           [FAILED]

 

Error 2:

[root@rcarter-sspPhantomDebugger-Centos6-x64 /]# service network restartShutting down interface eth0:  Error: Device 'eth0' (/org/freedesktop/NetworkManager/Devices/0) disconnecting failed: This device is not active
                                                           [FAILED]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0:  ipcalc: bad prefix: 255.255.255.0
RTNETLINK answers: File exists
Error adding address 192.168.6.95 for eth0.
RTNETLINK answers: File exists
                                                           [  OK  ]


To get around these errors I had to make a few changes to /etc/sysconfig/network-scripts/ifcfg-eth0:

  • Change PREFIX=255.255.255.0 to PREFIX=24
    .. This could also be fixed by changing to NETMASK=255.255.255.0

  • Change BOOTPROTO=static to BOOTPROTO=none

  • Remove the UUID=5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03 line