Network configuration on CentOS

network

Static IP address

Assigning a static IP address on CentOS is accomplished by editing the files in the directory /etc/sysconfig/network-scripts. For example, assign a static IP address to interface eth0 by editing /etc/sysconfig/network-scripts/ifcfg-eth0:

DEVICE=eth0
BOOTPROTO=none
IPADDR=192.168.0.123
NETMASK=255.255.255.0
GATEWAY=192.168.0.1
ONBOOT=yes

Network interface bonding

To achieve higher bandwidth and/or reliability, network interfaces can be bonded. First, edit the file /etc/sysconfig/network-scripts/ifcfg-bond0:

DEVICE=bond0
BOOTPROTO=none
IPADDR=10.0.0.1
NETMASK=255.255.255.0
ONBOOT=yes

After that, you need to edit the network interfaces that are part of this bond, e.g. eth1 and eth2. Let’s start with /etc/sysconfig/network-scripts/ifcfg-eth1:

DEVICE=eth1
BOOTPROTO=none
MASTER=bond0
SLAVE=yes
ONBOOT=yes

Then edit /etc/sysconfig/network-scripts/ifcfg-eth2:

DEVICE=eth2
BOOTPROTO=none
MASTER=bond0
SLAVE=yes
ONBOOT=yes

The last file to edit is /etc/modprobe.conf:

alias bond0 bonding
options bond0 mode=active-backup miimon=100

The mode value in this last file can be one of several:

  • balance-rr
  • active-backup
  • balance-xor
  • 802.3ad
  • balance-tlb
  • balance-alb

In the active-backup mode shown in the example, only one slave in the bond is active. A different slave becomes active if, and only if, the active slave fails. The bond’s MAC address is externally visible on only one port (network interface) to avoid confusing the switch.

The option miimon (media-independent interface monitoring) defines how often, in milliseconds, link monitoring occurs.

Leave a Reply

Your email will not be published. Name and Email fields are required.