can not ping or ssh to the instance: folsom + novanetwork

hello,
I installed openstack folsom with nova-network (not quantum)
I can successfully add an instance with private ip address
I also activated ports 22 and icmp in the default security group
when I try to ssh the instance : ssh -vvv -i /home/key.pem ubuntu@10.10.10.2
i got this error
OpenSSH_6.0p1 Debian-3ubuntu1, OpenSSL 1.0.1c 10 May 2012
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to 10.10.10.2 [10.10.10.2] port 22.
debug1: connect to address 10.10.10.2 port 22: No route to host
ssh: connect to host 10.10.10.2 port 22: No route to host
I can not also ping : From 10.10.10.1 icmp_seq=1 Destination Host Unreachable

my nova.conf :

[DEFAULT]
logdir=/var/log/nova
state_path=/var/lib/nova
lock_path=/run/lock/nova
verbose=True
api_paste_config=/etc/nova/api-paste.ini
scheduler_driver=nova.scheduler.simple.SimpleScheduler
s3_host=x.x.x.x
ec2_host=x.x.x.x
ec2_dmz_host=x.x.x.x
rabbit_host=x.x.x.x
cc_host=x.x.x.x
#osapi_compute_extension=nova.api.openstack.compute.contrib.standard_extensions
nova_url=http://x.x.x.x:8774/v1.1/
sql_connection=mysql://root:procan@x.x.x.x/nova
ec2_url=http://x.x.x.x:8773/services/Cloud

# Auth
use_deprecated_auth=false
auth_strategy=keystone
keystone_ec2_url=http://x.x.x.x:5000/v2.0/ec2tokens

# Imaging service
glance_api_servers=x.x.x.x:9292
image_service=nova.image.glance.GlanceImageService

# Virt driver
connection_type=libvirt
libvirt_type=kvm
libvirt_use_virtio_for_bridges=true
start_guests_on_host_boot=false
resume_guests_state_on_host_boot=false

# Vnc configuration

novnc_enabled=true
novncproxy_base_url=http://x.x.x.x:6080/vnc_auto.html
novncproxy_port=6080
vncserver_proxyclient_address=127.0.0.1
vncserver_listen=0.0.0.0

# Network settings
dhcpbridge_flagfile=/etc/nova/nova.conf
dhcpbridge=/usr/bin/nova-dhcpbridge
network_manager=nova.network.manager.FlatDHCPManager
public_interface=eth0
flat_interface=eth0
flat_network_bridge=br100
fixed_range=10.10.10.0/27
network_size=32
flat_network_dhcp_start=10.10.10.1
flat_injected=False
force_dhcp_release=true
rootwrap_config=/etc/nova/rootwrap.conf
# Cinder #
volume_api_class=nova.volume.cinder.API
enabled_apis=ec2,osapi_compute,metadata

thank you for your help