This guide will help you determine failures to your network interfaces in ClearOS.

A common problem for network cards is that the MAC addresses assigned by the system mismatch the MAC addresses on the NICs. This configuration error can cause your NICs to not work or not come online. This can be caused by, among other things, replacing the NICs or the motherboard that the NICs are on. This can even be caused by adding additional hardware that somehow inverts the detection order of the NICs on the bus.

First run through the Driver Message (sometimes called Display Message) system to see what messages were passed by the kernel driver system about the network cards when the system booted:

dmesg|less

Once in this display, you can use the arrow keys to navigate up and down. Use the 'q' key to quit. Use the '/' to search, example:

/eth

The '/eth' search will take you to the first instance of the string eth which might be talking about your eth devices. If not, press 'n' to search for the next iteration.

e1000e 0000:01:00.0: eth0: (PCI Express:2.5GT/s:Width x1) 00:90:fb:29:c9:68
e1000e 0000:01:00.0: eth0: Intel(R) PRO/1000 Network Connection
e1000e 0000:01:00.0: eth0: MAC: 3, PHY: 8, PBA No: 300020-000
e1000e 0000:02:00.0: Disabling ASPM L0s 
e1000e 0000:02:00.0: PCI->APIC IRQ transform: INT A -> IRQ 17
e1000e 0000:02:00.0: setting latency timer to 64
  alloc irq_desc for 27 on node -1
  alloc kstat_irqs on node -1
e1000e 0000:02:00.0: irq 27 for MSI/MSI-X
  alloc irq_desc for 28 on node -1
  alloc kstat_irqs on node -1
e1000e 0000:02:00.0: irq 28 for MSI/MSI-X
  alloc irq_desc for 29 on node -1
  alloc kstat_irqs on node -1
e1000e 0000:02:00.0: irq 29 for MSI/MSI-X
e1000e 0000:02:00.0: eth1: (PCI Express:2.5GT/s:Width x1) 00:90:fb:29:c9:69
e1000e 0000:02:00.0: eth1: Intel(R) PRO/1000 Network Connection
e1000e 0000:02:00.0: eth1: MAC: 3, PHY: 8, PBA No: 300020-000
e1000e 0000:03:00.0: Disabling ASPM L0s 
e1000e 0000:03:00.0: PCI->APIC IRQ transform: INT A -> IRQ 18
e1000e 0000:03:00.0: setting latency timer to 64
  alloc irq_desc for 30 on node -1
  alloc kstat_irqs on node -1
e1000e 0000:03:00.0: irq 30 for MSI/MSI-X
  alloc irq_desc for 31 on node -1
  alloc kstat_irqs on node -1
e1000e 0000:03:00.0: irq 31 for MSI/MSI-X
  alloc irq_desc for 32 on node -1
  alloc kstat_irqs on node -1

In the above example I can see that the kernel see NICs as:

• eth0 - 00:90:fb:29:c9:68
• eth1 - 00:90:fb:29:c9:69

Take note of these MAC addresses, we will next reference the system configuration files to determine if a misconfiguration is in place.

The directory which contains the configuration for the network interfaces is '/etc/sysconfig/network-scripts/'. Navigate there now:

cd /etc/sysconfig/network-scripts/

You can see your configured network cards by running:

ls ifcfg-eth*

To see the MAC address assignments within those files run:

grep HWADDR ifcfg-eth*

In our example, my addresses are listed as:

ifcfg-eth0:HWADDR="00:90:FB:29:C9:69"
ifcfg-eth1:HWADDR="00:90:FB:29:C9:68"

In this case, they are inverted and need to switched to match the order represented in 'dmesg'. Use your favorite editor (pico, nano, vi, emacs) to modify this file.

Once the file have been properly modified, restart the network service and firewall service.

service network restart
service firewall restart

Because so many subsystems rely on a properly configured network stack, you may want to restart the server in order to validate that everything comes up normally.

ClearOS Documentation … Knowledgebase … Troubleshooting