On Mar 18, 2014, at 7:40 AM, Roman Verchikov 
<rverchi...@mirantis.com<mailto:rverchi...@mirantis.com>> wrote:

Hi stakers,

We’re trying to replace dnsmasq-supplied DHCP for tenant VMs with a vendor’s 
baremetal DHCP server. In order to pass DHCP request to a vendor’s server and 
send DHCP response back to VM we decided to add another OVS bridge (we called 
it br-dhcp), connected to integration bridge (br-int), which will have OVS 
rules connecting VM’s MAC address with br-dhcp port. In this scenario DHCP 
response will only find it’s way back to a VM if VM has globally-unique MAC 
address.

My questions are:

  *   is having code which generates globally-unique MACs for VMs acceptable by 
the community at all?

This question tends to pop up from time to time and there are valid deployment 
and usage scenarios where you would want to assign the same MAC to multiple 
ports.


  *   is there a better solution to the problem (we also tried using dnsmasq as 
a DHCP relay there)?

That answer really depends on a number of factors.
 - Are the IP allocations being handled inside or outside of Neutron?
 - Do you allow different networks to have overlapping IP ranges?
 -

If it is outside of the OpenStack deployment then your code can use flow mods 
with you br-dhcp. If Neutron is managing the allocations or you allow 
overlapping IPs, you probably want to consider implementing a driver for the 
DHCP server.

mark

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