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On 26 November 2012 20:38, Gary Kotton <gkotton at redhat.com> wrote:

> If I understand correctly the IP address of the DHCP server is passed by
> Nova to the VM. Which IP address will this be? If a load balancer is used
> the address can be the same - that is a virtual IP.
>

Hm, define 'passed'.  Nova knows what it is for firewalling purposes.  It's
probably not so hard to change the DHCP address into a list of permitted
addresses.  The VM itself first receives the address as part of the
response; it certainly shouldn't be passed as config data of any form.

Assuming the two DHCP servers back on to the same database (and obviously
assuming the database itself is HA) then leases would be co-ordinated
between the two even with LB at work.  Generally we're not picking a random
address out of a pool and promising not to give it to anyone else; we're
providing an address we decided upon when the VM boot command was first
received, and we're just retrieving it at this point (albeit from a local
cache, as it's pushed into dnsmasq rather than retrieved from the DB on
demand).
-- 
Ian.
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