ifconfig output:
============================================================================
ubuntu@juju-machine-4-lxd-3:/etc/network/interfaces.d$ ifconfig
eth0      Link encap:Ethernet  HWaddr 00:16:3e:84:70:09  
          inet addr:10.244.192.235  Bcast:10.244.255.255  Mask:255.255.192.0
          inet6 addr: fe80::216:3eff:fe84:7009/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:393978 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3339 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:98808309 (98.8 MB)  TX bytes:397911 (397.9 KB)

eth1      Link encap:Ethernet  HWaddr 00:16:3e:9e:20:7a  
          inet addr:10.244.192.236  Bcast:0.0.0.0  Mask:255.255.192.0
          inet6 addr: fe80::216:3eff:fe9e:207a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:419383 errors:0 dropped:0 overruns:0 frame:0
          TX packets:36828 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:53405834 (53.4 MB)  TX bytes:8480222 (8.4 MB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
============================================================================

config files:
============================================================================
ubuntu@juju-machine-4-lxd-3:/etc/network/interfaces.d$ cat *

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual
  dns-nameservers 10.244.192.10
  dns-search oilstaging
  pre-up ip address add 10.244.192.235/18 dev eth0 || true
  up ip route replace 10.244.192.0/18 dev eth0 || true
  down ip route del 10.244.192.0/18 dev eth0 || true
  post-down address del 10.244.192.235/18 dev eth0 || true
  up ip route replace default via 10.244.192.1 || true
  down ip route del default via 10.244.192.1 || true

auto eth1
iface eth1 inet manual
  pre-up ip address add 10.244.192.236/18 dev eth1 || true
  up ip route replace 10.244.192.0/18 dev eth1 || true
  down ip route del 10.244.192.0/18 dev eth1 || true
  post-down address del 10.244.192.236/18 dev eth1 || true
============================================================================

# The primary network interface
auto eth0
iface eth0 inet dhcp

route -n on the container:
============================================================================
ubuntu@juju-machine-4-lxd-3:/etc/network/interfaces.d$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.244.192.1    0.0.0.0         UG    0      0        0 eth0
10.244.192.0    0.0.0.0         255.255.192.0   U     0      0        0 eth1
10.244.192.0    0.0.0.0         255.255.192.0   U     0      0        0 eth1
10.244.192.0    0.0.0.0         255.255.192.0   U     0      0        0 eth0
============================================================================

and on the host:
============================================================================
ubuntu@puritanvm07:~$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.244.192.1    0.0.0.0         UG    0      0        0 br-eth0
10.0.3.0        0.0.0.0         255.255.255.0   U     0      0        0 lxcbr0
10.0.4.0        0.0.0.0         255.255.255.0   U     0      0        0 lxdbr0
10.244.192.0    0.0.0.0         255.255.192.0   U     0      0        0 br-eth0
10.244.192.0    0.0.0.0         255.255.192.0   U     0      0        0 br-eth1
============================================================================