Here is the output from some various networking commands on a cavium host deployed with juju,  not the juju-br0 issues as discussed with andrew and dimiter

ubuntu@cvm6:~$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         10.110.24.1     0.0.0.0         UG        0 0          0 eth1
10.110.24.0     0.0.0.0         255.255.248.0   U         0 0          0 juju-br0
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ cat /etc/network/interfaces
auto lo

iface eth0 inet dhcp





iface eth2 inet dhcp

# Primary interface (defining the default route)
iface eth1 inet manual

# Bridge to use for LXC/KVM containers
auto juju-br0
iface juju-br0 inet dhcp
    bridge_ports eth1
ubuntu@cvm6:~$ ip route
default via 10.110.24.1 dev eth1 
10.110.24.0/21 dev juju-br0  proto kernel  scope link  src 10.110.24.116 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ sudo less /var/log/syslog 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ 
ubuntu@cvm6:~$ ifconfig
eth1      Link encap:Ethernet  HWaddr 48:ce:e4:26:d0:c0  
          inet addr:10.110.24.116  Bcast:10.110.255.255  Mask:255.255.248.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:6183 errors:0 dropped:48 overruns:0 frame:0
          TX packets:4767 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:619071 (619.0 KB)  TX bytes:732605 (732.6 KB)

juju-br0  Link encap:Ethernet  HWaddr 48:ce:e4:26:d0:c0  
          inet addr:10.110.24.116  Bcast:10.110.255.255  Mask:255.255.248.0
          inet6 addr: fe80::4ace:e4ff:fe26:d0c0/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5660 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3605 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:399291 (399.2 KB)  TX bytes:628905 (628.9 KB)

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:482 errors:0 dropped:0 overruns:0 frame:0
          TX packets:482 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:42532 (42.5 KB)  TX bytes:42532 (42.5 KB)

ubuntu@cvm6:~$ sudo dhclient -v ^C
ubuntu@cvm6:~$ sudo brtctl show
sudo: brtctl: command not found
ubuntu@cvm6:~$ sudo brctl show
bridge name	bridge id		STP enabled	interfaces
juju-br0		8000.48cee426d0c0	no		eth1
ubuntu@cvm6:~$ sudo brctl show macs
bridge name	bridge id		STP enabled	interfaces
macs		can't get info No such device
ubuntu@cvm6:~$ sudo brctl showmacs
Incorrect number of arguments for command
Usage: brctl showmacs <bridge>		show a list of mac addrs
ubuntu@cvm6:~$ sudo brctl showmacs juju-br0
port no	mac addr		is local?	ageing timer
  1	18:35:75:f5:ed:d0	no		   0.07
  1	40:a8:f0:20:29:ad	no		   0.67
  1	48:ce:e4:26:d0:c0	yes		   0.00
  1	48:ce:e4:26:d0:c0	yes		   0.00
  1	52:40:1e:11:89:d0	no		 146.25
  1	6a:e3:d5:af:3f:74	no		   0.01
  1	a0:55:4f:97:47:6c	no		  19.66
  1	a0:55:4f:97:47:6d	no		  19.66
  1	fc:aa:14:9a:16:84	no		  10.49
  1	fc:aa:14:9d:bb:e0	no		   6.01
  1	fc:aa:14:9d:bc:c4	no		  63.30
  1	fc:aa:14:9d:bd:18	no		  64.30
  1	fc:aa:14:9d:bd:1e	no		  25.84
  1	fc:aa:14:9d:bd:36	no		  88.42
  1	fc:aa:14:9d:bd:48	no		  23.38
ubuntu@cvm6:~$ sudo arp 
Address                  HWtype  HWaddress           Flags Mask            Iface
10.110.24.1              ether   40:a8:f0:20:29:ad   C                     juju-br0
cvm8.cavium              ether   6a:e3:d5:af:3f:74   C                     juju-br0
cvm8.cavium                      (incomplete)                              eth1
10.110.24.1                      (incomplete)                              eth1