/etc/network/interfaces

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
#0
allow-hotplug eth2
iface eth2 inet dhcp

#auto eth1
#iface eth1 inet static
#address 192.168.1.49
#netmask 255.255.255.0
#gateway 192.168.1.50

#auto eth1
#iface eth1 inet static
#address 192.168.1.50
#netmask 255.255.255.0
##gateway 192.168.1.50

auto eth1
auto eth2
auto eth3

auto bond0
iface bond0 inet static
address 192.168.1.50
netmask 255.255.255.0
network 192.168.1.0
slaves eth0 eth1
bond_mode active-backup
bond_miimon 100
bond_downdelay 200
bond_updelay 200