weslambert edited this page May 31, 2018 · 8 revisions
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Disabling the graphical Network Manager and configuring networking from the command line

If you're running Security Onion 14.04/16.04, 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

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

# 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:

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: