[Pacemaker] Corosync over DHCP IP

[Dejan Muhamedagic]

Hi,

On Tue, Feb 12, 2013 at 02:52:58PM +0100, Dennis Jacobfeuerborn wrote:
> On 02/12/2013 03:15 AM, Andrew Beekhof wrote:
> > On Tue, Feb 12, 2013 at 1:01 PM, Dennis Jacobfeuerborn
> > <dennisml at conversis.de> wrote:
> >> On 02/12/2013 02:38 AM, Andrew Beekhof wrote:
> >>> On Tue, Feb 12, 2013 at 3:09 AM, Dennis Jacobfeuerborn
> >>> <dennisml at conversis.de> wrote:
> >>>> On 02/11/2013 11:30 AM, Andrew Beekhof wrote:
> >>>>> On Mon, Feb 11, 2013 at 9:24 PM, Viacheslav Biriukov
> >>>>> <v.v.biriukov at gmail.com> wrote:
> >>>>>> It is VM in the OpenStack. So we can't use static IP.
> >>>>>> Right now investigating why interface become down.
> >>>>>
> >>>>> Even if you solve that, dynamic IP addresses are fundamentally
> >>>>> incompatible with cluster software.
> >>>>> You're effectively trying to create a cluster out of nodes which
> >>>>> change their name every time they boot.
> >>>>
> >>>> DHCP doesn't necessarily mean a dynamic IP.
> >>>
> >>> In most (if not all) openstack deployments, it does.
> >>> Even better, the static IPs you can assign belong to the physical
> >>> hosts and don't show up inside the guests - so corosync can't bind to
> >>> them.
> >>
> >> You are probably talking about the floating IPs. The primary IPs (usually
> >> in the 10.0.0.0/8 range) of the interfaces however should work fine for
> >> this. There's no magic involved.
> > 
> > If they don't show up in 'ip addr', which they don't in openstack
> > guests, then corosync can't use them.
> > There is no way to say "Your address is w.x.y.z but you'll get
> > messages on a.b.c.d".
> 
> They show up like like any other interface in 'ip addr'. There is no magic
> involved in any of this.
> The machine gets assigned a primary IP from the assigned network which is
> stored in the dhcp leases database and usually (but not necessarily) it
> gets assigned a floating ip that is reachable from the internet which is
> NATed to the primary IP.
> When the guest boots it discovers its primary IP via dhcp and assignes that
> IP to eth0.
> There is no reason why corosync shouldn't be able to use that IP to address
> the cluster nodes.

As long as the lease time exceeds the node's uptime :)

Thanks,

Dejan

> Regards,
>   Dennis
> 
> 
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