Please find alternative network setups for containers on the LXC mainpage.

In case of bridged or routed network provided by the host, here is an example.

Host device as bridge

# The primary network interface
#allow-hotplug eth0
#iface eth0 inet dhcp

auto br0
iface br0 inet dhcp
        bridge_ports eth0
        bridge_fd 0
        bridge_maxwait 0

# uncomment the below and comment the above for static ip setup on the host
#iface br0 inet static
#       bridge_ports eth0
#       bridge_fd 0
#       address <host IP here, e.g. 10.1.1.2>
#       netmask 255.255.255.0
#       network <network IP here, e.g. 10.1.1.0>
#       broadcast <broadcast IP here, e.g. 10.1.1.255>
#       gateway <gateway IP address here, e.g. 10.1.1.1>
#       # dns-* options are implemented by the resolvconf package, if installed
#       dns-nameservers <name server IP address here, e.g. 10.1.1.1>
#       dns-search your.search.domain.here

Additonal bridge device instead of changing a host device to br0

natted

routed

References :