HI everyone,
i installed Openstack juno all-in-one in a single VM using the RDO packstack. i configured the external bridge to meet the configuration of my environment then i wanted to create the external network from the begining so i deleted the default network and also the router. when i tried to create a new external network i encounter the error :

create failed (client error): Invalid input for operation: network_type value 'flat' not supported.

the log of network server shows

2015-04-28 15:44:06.994 2705 INFO oslo.messaging._drivers.impl_rabbit [req-bf689ebc-3cd7-416d-96bf-385783921998 ] Connected to AMQP server on 10.0.2.15:5672
2015-04-28 15:44:07.100 2705 INFO neutron.api.v2.resource [req-bf689ebc-3cd7-416d-96bf-385783921998 None] create failed (client error): Invalid input for operation: network_type value 'flat' not supported.
2015-04-28 15:44:07.106 2705 INFO neutron.wsgi [req-bf689ebc-3cd7-416d-96bf-385783921998 None] 10.0.2.15 - - [28/Apr/2015 15:44:07] "POST //v2.0/networks.json HTTP/1.1" 400 363 1.144523
2015-04-28 15:44:07.147 2705 INFO neutron.wsgi [-] (2705) accepted ('10.0.2.15', 45508)
2015-04-28 15:44:07.167 2705 INFO neutron.wsgi [req-8f28c53d-8245-4436-80a8-e82863db3dfe None] 10.0.2.15 - - [28/Apr/2015 15:44:07] "GET //v2.0/extensions.json HTTP/1.1" 200 4326 0.018893
2015-04-28 15:44:07.168 2705 INFO neutron.wsgi [-] (2705) accepted ('10.0.2.15', 45509)
2015-04-28 15:44:07.200 2705 INFO neutron.wsgi [req-dc9aee1e-79b1-436b-a71a-4a4150a232e7 None] 10.0.2.15 - - [28/Apr/2015 15:44:07] "GET //v2.0/networks.json HTTP/1.1" 200 229 0.030729
2015-04-28 15:44:07.212 2705 INFO neutron.wsgi [-] (2705) accepted ('10.0.2.15', 45510)
2015-04-28 15:44:07.270 2705 INFO neutron.wsgi [req-56e6ac00-ed90-4c72-a003-2f26e95cf9b4 None] 10.0.2.15 - - [28/Apr/2015 15:44:07] "GET //v2.0/subnets.json HTTP/1.1" 200 228 0.057074

my interfaces configuration is :

br-ex: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.2.15  netmask 255.255.255.0  broadcast 10.0.2.255
        inet6 fe80::9829:caff:fe2d:4844  prefixlen 64  scopeid 0x20<link>
        ether 08:00:27:4b:70:6f  txqueuelen 0  (Ethernet)
        RX packets 631  bytes 3421963 (3.2 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 571  bytes 101673 (99.2 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::a00:27ff:fe4b:706f  prefixlen 64  scopeid 0x20<link>
        ether 08:00:27:4b:70:6f  txqueuelen 1000  (Ethernet)
        RX packets 2843  bytes 3541411 (3.3 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 582  bytes 131573 (128.4 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

enp0s8: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.57.113  netmask 255.255.255.0  broadcast 192.168.57.255
        inet6 fe80::a00:27ff:fec9:7290  prefixlen 64  scopeid 0x20<link>
        ether 08:00:27:c9:72 ...