NetworkConfiguration

Disabling the graphical Network Manager and configuring networking from the command line

If you're running Security Onion 12.04/14.04, all of this configuration will happen automatically if you choose "Yes, configure /etc/network/interfaces" in the Setup wizard.

NOTE! You may lose network connectivity during this process! Have a backup plan if attempting over SSH!

Stop Network Manager:

sudo /etc/init.d/network-manager stop

Prevent Network Manager from starting at next boot:

sudo mv /etc/init/network-manager.conf /etc/init/network-manager.conf.DISABLED

Next, configure your network interfaces in /etc/network/interfaces.

####Management interface#### You'll want a management interface (preferably connected to a dedicated management network) using either DHCP OR preferably static IP.

####Sniffing interface(s)#### You'll want one or more interfaces dedicated to sniffing (no IP address). NIC offloading functions such as tso, gso, and gro should be disabled to ensure that Snort/Suricata get an accurate view of the traffic (see http://blog.securityonion.net/2011/10/when-is-full-packet-capture-not-full.html).

####Sample /etc/network/interfaces####

auto lo

iface lo inet loopback



# Management interface using DHCP (not recommended due to Bro issue described above)

auto eth0

iface eth0 inet dhcp



# OR 



# Management interface using STATIC IP (instead of DHCP)

auto eth0

iface eth0 inet static

  address 192.168.1.14

  gateway 192.168.1.1

  netmask 255.255.255.0

  network 192.168.1.0

  broadcast 192.168.1.255

  # If running Security Onion 14.04, you'll need to configure DNS here

  dns-nameservers 192.168.1.1 192.168.1.2



# AND one or more of the following



# Connected to TAP or SPAN port for traffic monitoring

auto eth1

iface eth1 inet manual

  up ifconfig $IFACE -arp up

  up ip link set $IFACE promisc on

  down ip link set $IFACE promisc off

  down ifconfig $IFACE down

  post-up for i in rx tx sg tso ufo gso gro lro; do ethtool -K $IFACE $i off; done

  # If running Security Onion 14.04, you should also disable IPv6 as follows:

  post-up echo 1 > /proc/sys/net/ipv6/conf/$IFACE/disable_ipv6

You may also want to set the RX buffer size in the post-up command like this:

post-up ethtool -G $IFACE rx 4096; for i in rx tx sg tso ufo gso gro lro; do ethtool -K $IFACE $i off; done

Note that 4096 is just an example and your NIC may have a different maximum rx size. To determine the maximum rx setting for your NIC:

ethtool -g ethX

If necessary, configure DNS in /etc/resolv.conf:
http://en.wikipedia.org/wiki/Resolv.conf
http://www.cyberciti.biz/tips/howto-ubuntu-linux-convert-dhcp-network-configuration-to-static-ip-configuration.html
http://manpages.ubuntu.com/manpages/lucid/man5/resolver.5.html

Restart networking:

sudo /etc/init.d/networking restart

If you already had sensors running on these interfaces, you should restart them:

sudo nsm_sensor_ps-restart

For more information on network configuration in Ubuntu, please see:
https://help.ubuntu.com/community/NetworkConfigurationCommandLine/Automatic