My containers cannot ping each other

[falves1]

I have 10 containers, all with public IPs. some containers can ping from A to B, but pinging fails when tried from B to A.
I am using veth and a regular Linux bridge
auto br0
iface br0 inet manual
bridge-ports eth1
bridge-stp off
bridge-fd 0
bridge_maxwait 0

lxc.net.0.type = veth
lxc.net.0.flags = up
lxc.net.0.link = br0
lxc.net.0.name = eth0
lxc.net.0.l2proxy=1

What is the best configuration so my containers can talk to each other?