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[<Adrian_F_Smith@xxxxxxxx>]

FWIW I've tested the setup you describe and I'm not seeing duplicate ICMP replies. Unfortunately I can't offer an explanation.

Adrian

From: openstack-bounces+adrian_f_smith=dell.com@xxxxxxxxxxxxxxxxxxx [mailto:openstack-bounces+adrian_f_smith=dell.com@xxxxxxxxxxxxxxxxxxx] On Behalf Of Shyam Kaushik
Sent: Friday, October 14, 2011 2:00 PM
To: openstack@xxxxxxxxxxxxxxxxxxx
Subject: [Openstack] Duplicate ICMP due to public interface bridge being placed in promiscus mode

Hi Vish,

In our openstack deployment we observe this:

Since linux_net.py/initialize_gateway_device()<http://linux_net.py/initialize_gateway_device()> does this
    # NOTE(vish): If the public interface is the same as the
    #             bridge, then the bridge has to be in promiscuous
    #             to forward packets properly.
    if(FLAGS.public_interface == dev):
        _execute('ip', 'link', 'set',
                     'dev', dev, 'promisc', 'on', run_as_root=True)


Any VM spawned on the cloud controller node if it sends an ICMP ping to an external network gets duplicate replies (i.e. there are 2 replies for the same ICMP request). For VM's spawned on any other non-cloud controller this doesn't happen.

If we turn of promiscus mode on the bridge, the VM on cloud controller doesn't see the duplicate replies, but VM's on non-cloud controller cannot reach external network.

Question to you is, is this duplicate ICMP replies expected for VM's running on cloud controller due to above logic?

--Shyam