THanks for the answer, my env is actually running test after applying https://github.com/openvswitch/ovs/commit/e120ff1f8e4dbb0b889b26e0be082376a32090bc
so can't restart neutron agent (a different story) 
 
I will post what we saw when stop neutorn agent when the system finish the test, basically, the br-ex flow will be wiped out unless you restart neutorn-ovs-agent... thanks
 
Ji Chen
z Infrastructure as a Service architect
Phone: 10-82451493
 
 
----- Original message -----
From: Slawek Kaplonski <skaplons@redhat.com>
To: Chen CH Ji <jichenjc@cn.ibm.com>
Cc: openstack-discuss@lists.openstack.org
Subject: [EXTERNAL] Re: [openstack-discuss][neutron] is neutron-openvswitch-agent needed for network connection on provider network?
Date: Mon, Feb 24, 2020 6:03 PM
 
Hi,

It isn’t expected behaviour that data plane is broken just because neutron-ovs-agent is stopped. Agent should configure flows/iptables/ports and it should works even if agent is down.
Can You check exactly what is causing packet drops? Is it some missing open flow rule, something in iptables? Or maybe something else?

> On 21 Feb 2020, at 10:17, Chen CH Ji <jichenjc@cn.ibm.com> wrote:
>
> We are running provider network with VLAN /FLAT, does the neutron-openvswitch-agent is mandatory to be running in order to make the VM deployed able to connect outside?
>  
> e.g. I have a VM   instance-00000027, I login the VM and ping out side, in the mean time, use another session to
> systemctl stop  neutron-openvswitch-agent.service then wait for a few minutes, the ping will stop, does this is an expected behavior?
> I know nova-compute is not running won't affect VM functionality, but does neutron openvswitch agent is needed or not? Thanks a lot
>  
> [root@kvm02 ~]# virsh list
>  Id   Name                State
> -----------------------------------
>  4    instance-00000027   running
>  
> [root@kvm02 ~]# virsh console 4
> Connected to domain instance-00000027
> Escape character is ^]
> [root@dede ~]# ping
> [root@dede ~]# ping 172.16.32.1
> PING 172.16.32.1 (172.16.32.1) 56(84) bytes of data.
> 64 bytes from 172.16.32.1: icmp_seq=1 ttl=64 time=19.8 ms
> 64 bytes from 172.16.32.1: icmp_seq=2 ttl=64 time=0.667 ms
> 64 bytes from 172.16.32.1: icmp_seq=3 ttl=64 time=0.774 ms
>  
> Ji Chen
> z Infrastructure as a Service architect
> Phone: 10-82451493
> E-mail: jichenjc@cn.ibm.com
>


Slawek Kaplonski
Senior software engineer
Red Hat