I have deployed using kolla so openstack services are running in containers. I have one control node and one compute node.

in my globals.yml I set em1 as my network_interface and I set em2 as my neutron_external_interface

ifcfg-em1 configuration:

DEVICE="em1"
ONBOOT=yes
NETBOOT=yes
UUID="f75d9728-7e01-4b03-90a1-790b377c4465"
IPV6INIT=no
BOOTPROTO=none
TYPE=Ethernet
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV4_ROUTE_METRIC=100
IPV4_DNS_PRIORITY=100
DNS1=172.28.0.100
IPADDR=172.28.9.5
PREFIX=24
GATEWAY=172.28.9.1

ifcfg-em2 configuration:

TYPE=OVSPort
DEVICETYPE=ovs
OVS_BRIDGE=br-ex
NAME=em2
UUID=d1c9d522-aa05-4c2e-9ee7-3369eee04bc6
DEVICE=em2
ONBOOT=yes
NM_CONTROLLED=no
BOOTPROTO=none

Here is the ovs-vsctl show output from the control node which is running the network services:

[root@openstackcontroller network-scripts]# docker exec -ti openvswitch_vswitchd ovs-vsctl show
59269da8-6cdc-4fbf-a8f9-e1f5448f8452
    Manager "ptcp:6640:127.0.0.1"
        is_connected: true
    Bridge br-ex
        Controller "tcp:127.0.0.1:6633"
            is_connected: true
        fail_mode: secure
        Port "em2"
            Interface "em2"
        Port phy-br-ex
            Interface phy-br-ex
                type: patch
                options: {peer=int-br-ex}
        Port br-ex
            Interface br-ex
                type: internal
    Bridge br-tun
        Controller "tcp:127.0.0.1:6633"
            is_connected: true
        fail_mode: secure
        Port patch-int
            Interface patch-int
                type: patch
                options: {peer=patch-tun}
        Port "vxlan-ac1c0906"
            Interface "vxlan-ac1c0906"
                type: vxlan
                options: {df_default="true", in_key=flow, local_ip="172.28.9.5", out_key=flow, remote_ip="172.28.9.6"}
        Port br-tun
            Interface br-tun
                type: internal
    Bridge br-int
        Controller "tcp:127.0.0.1:6633"
            is_connected: true
        fail_mode: secure
        Port "qr-c7a6dcf0-5b"
            tag: 4
            Interface "qr-c7a6dcf0-5b"
                type: internal
        Port "tap5ae8cbc8-df"
            tag: 4
            Interface "tap5ae8cbc8-df"
                type: internal
        Port patch-tun
            Interface patch-tun
                type: patch
                options: {peer=patch-int}
        Port "qg-2bfa4de4-ac"
            tag: 5
            Interface "qg-2bfa4de4-ac"
                type: internal
        Port int-br-ex
            Interface int-br-ex
                type: patch
                options: {peer=phy-br-ex}
        Port br-int
            Interface br-int
                type: internal
        Port "tapb0a96682-54"
            tag: 5
            Interface "tapb0a96682-54"
                type: internal

It says that the br-ex has em2 as a port

Bridge br-ex
        Controller "tcp:127.0.0.1:6633"
            is_connected: true
        fail_mode: secure
        Port "em2"
            Interface "em2"

So why doesn't br-ex show that its up when I do ip a on the control node like below

[root@openstackcontroller network-scripts]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: em1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether d4:ae:52:6f:49:33 brd ff:ff:ff:ff:ff:ff
    inet 172.28.9.5/24 brd 172.28.9.255 scope global em1
       valid_lft forever preferred_lft forever
    inet 172.28.9.139/32 scope global em1
       valid_lft forever preferred_lft forever
    inet6 fe80::d6ae:52ff:fe6f:4933/64 scope link
       valid_lft forever preferred_lft forever
3: em2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master ovs-system state UP qlen 1000
    link/ether d4:ae:52:6f:49:34 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::d6ae:52ff:fe6f:4934/64 scope ...