Failover strangeness
Greg G
ggersh at ctc.net
Wed Oct 11 16:28:30 UTC 2006
David W. Hankins wrote:
> On Tue, Oct 10, 2006 at 04:17:38PM -0400, Greg G wrote:
>
>> Greg G wrote:
>>
>>> The lease didn't transition back, even after a few hours, and the
>>> peer went down. Is there a way to make that transition happen?
>>>
>
> If the server is in partner-down state (not communications-interrupted),
>
The server did go to communications-interrupted state. I never saw
a partner-down state.
> I think it should happen after STOS+MCLT.
>
>
STOS? I'm not familiar with that. I see a reference to it in the
dhcpd man page, but not the dhcpd.conf. I couldn't figure out what the
key is for the failover-state object to look at it through omshell. I
had hoped it was "name", but that doesn't appear to be so.
Here's what I get in the leases file on the secondary when the
primary stops and then starts:
failover peer "ontdhcp" state {
my state communications-interrupted at 3 2006/10/11 16:19:28;
partner state normal at 1 2006/10/09 18:44:33;
mclt 30;
}
failover peer "ontdhcp" state {
my state normal at 3 2006/10/11 16:20:48;
partner state normal at 1 2006/10/09 18:44:33;
mclt 30;
}
I can wait hours, but the lease will never go back over to being
handled by the primary...
> If it doesn't, that's probably a bug.
>
I'm inclined to think so, but I wouldn't press the issue. :)
The really strange things is that if the secondary goes down and the
primary complains, when the secondary comes back up, the primary takes
control of the lease again!
> You're running into odd siutations here because failover isn't really
> designed for one-lease pools like this.
>
> Failover survivability all hinges around having a number of leases (free
> and backup states) allocated to each server in the event they should
> lose contact with the other.
>
> When there's only one, that will never be better than a single point of
> failure.
>
>
Hmmm. I'm really looking for redundancy, so that either of the dhcp
servers can serve up the lease for these clients. Both servers are
getting the request (via ip-helper), and I don't want both of them
offering the lease. That could get ugly.
> Although you could experiment with 'reserved' dynamic leases, which
> by definition are covered by both the 'free' and 'backup' states
> simultaneously.
>
>
No joy, unless I did it wrong. I put in the "infinite-is-reserved'
in the shared-network scope on both servers.
Thanks.
-Greg G
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