[Openstack] [Neutron] [nova-net] Setting up neutron within a guest.

Michael Turek mjturek at linux.vnet.ibm.com
Tue Aug 11 15:43:58 UTC 2015

Hey all,

Sorry for the lengthy email, just trying to explain my issue the best 
that I can.

I'm trying to run devstack with neutron within a guest.

The host of this guest is a Ubuntu 14.04 machine devstack running 
nova-net. To simplify setup and teardown of devstack within this guest, 
I add an OVS bridge to eth0 (br0) and specify it within the localrc. 
This allows stack.sh and unstack.sh to run without losing ssh access to 
the guest/machine. Basically, I'm stuck at getting a DHCP request from 
the guest's OVS bridge honoured by the host's nova-net. Here's what happens:

1) I spawn the guest (Ubuntu 14.04) and it's properly networked (Can 
ping it and ssh to it from outside the host).
2) I then install openvswitch and add the OVS bridge (sudo ovs-vsctl 
add-br br0; sudo ovs-vsctl add-port br0  eth0)\
3) Of course eth0 then loses connectivity. So I use the following 
/etc/network/interfaces file to remove eth0's IP and set it to 
promiscuous mode. It  also sets the bridge to use DHCP and sets it to 
promiscuous mode.

|#eth0 set to manual, br0 set to dhcp
# The loopback network interface
auto  lo
iface lo inet loopback
# The primary network interface
auto  eth0
# iface eth0 inet dhcp
iface eth0 inet manual
up ifconfig $IFACE0.0.0.0  up
up ip linkset  $IFACE promisc on
down ip linkset  $IFACE promisc off
down ifconfig $IFACE down
auto  br0
iface br0 inet dhcp
up ip linkset  $IFACE promisc on


4) I then cycle br0 and eth0. As expected eth0 loses it's IP and is set 
to promisc on. *br0 then issues a DHCP request which never gets 
honoured*. This is where I'm stuck. Any ideas?

*Also worth noting*, I've tried using neutron on the host which was a 
bit more successful. Neutron has a concept of ports where you can 
specify MACs to serve. I added the OVS bridge's MAC address to the port 
list and DHCP requests were fulfilled. However, the bridge could not 
ping in or out after receiving its IP. Does nova-net have something 

I also posted about it here, so if you want more info this might be 

If you need any other info, more detail, etc. Please do not hesitate to 
ask, I really appreciate any help!

Mike Turek
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