[lvs-users] keepalived - VRRP setup with no master

campbell mcleay campbell.mcleay at gmail.com
Fri Jul 9 12:56:37 BST 2010

Hi Sander,

Thanks for the reply. I was reading through the man page for
keepalived.conf and noticed the 'nopreempt' option just after I sent
the mail.



On Thu, Jul 8, 2010 at 10:08 PM, Sander Klein <roedie at roedie.nl> wrote:
> Hi,
> On Thu, 8 Jul 2010 20:17:33 +0100, campbell mcleay
> <campbell.mcleay at gmail.com> wrote:
>> I was interested in setting up LVS-NAT with keepalived for a redundant
>> setup. All of the documentation recommends one director designated as
>> master and one as backup. However, I was wondering if there is an
>> issue having both as backup, the reasons for this configuration being
>> 1) that config can be synced between the two directors, and 2) that if
>> the master goes down and comes backup, it would not mean that the
>> master would then take over again. I have read having the same
>> priority could result in a race condition, but wouldn't this be very
>> unlikely, since it would require both to come up at exactly the same
>> time. I have not found any one else with such a setup, and all
>> documentation says there has to be a master and backup with different
>> priorities, so I want to be careful that I haven't missed something.
>> It seems to work ok in practise so far though.
> This question might better be asked on the keepalived mailing list. Maybe
> someone has a better answer there than I have now.
> I think you can give both directors the same priority. A director that is
> in backup state and receives a vrrp packet with the same priority as it's
> own should stay in backup state. But I can imagine it is possible that both
> directors get in a state that they both start flapping between master and
> backup state. I didn't look at any code, I only quickly reviewed the RFC.
> So it might as well just work.
> About your second point. You could use the 'nopreempt' option in the
> keepalived config to keep a director with a higher priority from becoming a
> master. So, when the directors initially start the director with the
> highest priority becomes master. The master fails, so the director with the
> lower priority becomes master. When the director with the higher priority
> comes back online again it will become a backup director and stays backup
> until the director with the lower priority fails.
> Greets,
> Sander
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