Open Stack

Hi Akshay,

In most cases, you won’t have IP addresses configured on interfaces used by Neutron.

The Neutron L2 agents set up or configure the virtual bridges/switches on the host based on the type of network in use (VLAN, FLAT, VXLAN, etc). In many cases, an external provider network may be setup as a VLAN network. In that case, the VLAN ID must correspond to the VLAN configured on the physical switch that corresponds to your external network connected to the external router. The Neutron virtual router will connect to a virtual switch/bridge that effectively “bridges” the virtual network with the physical network. When that happens, your physical router and your virtual router will be in the same Layer 2 broadcast domain and Layer 3 network. Thus, when you have floating IPs configured,they would come from the ‘external’ network/pool and your physical router would send ARP requests for those addresses. The virtual router would send ARP replies and the traffic would be forwarded and NAT’d accordingly.

Of course, all of this working depends on Neutron having been configured appropriately and the networks created with the proper provider attribute values.

Hope that helps,

James


From: Akshay Kumar Sanghai <akshaykumarsanghai at gmail.com<mailto:akshaykumarsanghai at gmail.com>>
Date: Friday, January 15, 2016 at 3:13 PM
To: "openstack at lists.openstack.org<mailto:openstack at lists.openstack.org>" <openstack at lists.openstack.org<mailto:openstack at lists.openstack.org>>
Subject: [Openstack] [openstack][neutron]external network packets to network node

Hi,
I have done a kilo ubuntu installation of openstack. One thing i noticed was the network node's external interface is unnumbered. Then how does the external router forwards the packet to the network node? Suppose a vm has a floating ip . I send a packet to that vm using the floating ip. The nat happens at the network node. How does the packet reached the network node as there is no ip assigned to the interface. I have not configured dvr and l3 agent is running on network node.

Thanks,
Akshay
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