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List:       keepalived-devel
Subject:    [Keepalived-devel] Two servers, equal priority,
From:       Daniel Pittman <daniel () rimspace ! net>
Date:       2010-09-15 2:29:47
Message-ID: 87iq2791t0.fsf () rimspace ! net
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G'day.

We recently ran into a problem which I *think* is in our own deployment, and
which I wanted to check if it was (a) actually our fault, and (b) not actually
going to come back and bite us again.

(In other words: if my reasoning is wrong, please tell me, so I can continue
 to work out what is going wrong and get it genuinely fixed. :)

Specifically: we have two servers using keepalived for VRRP only.
They had identical priority (100), and both were set to a default state of
MASTER.

Both were running keepalived 1.1.15-1 from Debian/Lenny.

When they were brought up they did *not* hold an election, but instead both
brought up the default interface, even though they could see the communication
from the other router.

My guess is that because there was no other selector, and both were in MASTER,
they didn't trigger any cause for an election on startup; this was supported
by the fact that they *would* behave if anything perturbed the situation into
the future: it was only when both came up from cold start and were in
communication successfully that we saw this.


We could resolve this by putting them both into a default BACKUP state, or by
giving them different priorities, since either of those caused them to
determine that an election was required and, then, to work.


The configuration for the VRRP was as follows, identical on both machines:

    vrrp_instance VI_3 {
        state                       MASTER
        interface                   eth0
        virtual_router_id           3
        priority                    100
        advert_int                  1
        authentication {
            auth_type               PASS
            auth_pass               WHATEVER
        }
        virtual_ipaddress {
            192.168.1.140/32 dev eth0 label eth0:3
        }
    }


Regards,
        Daniel
-- 
✣ Daniel Pittman            ✉ daniel@rimspace.net            ☎ +61 401 155 707
               ♽ made with 100 percent post-consumer electrons


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