Frustrated DHCP failover not working.. :(
rmorin at datavalet.com
Wed Feb 10 17:48:22 UTC 2016
Hey Niall, thanks fro your prompt reply... :)
Your suggestion is interesting, however currently our controllers only
point to dhcp-2 server and not to both, so making dhcp-1 primary before
we modify the controllers to go to both machines, would not work.
Pretty much what i was trying to do is to keep dhcp-2 server secondary,
and sync it up with dhcp-1, even though dhcp-1 is not giving out any
leases, because no traffic goes to it currently, as all traffic goes to
Downtime must be kept to a min as we normally have 10'000s of request at
any given time to these dhcp servers. Thats why i wanted to keep djcp-2
secondary and dhcp-1 primary as no requests go to dhcp-1 now, once
dhcp-1 looks like its communicating with dhcp-2 ok, then we would direct
some controllers to send requests to both servers rather than just the
I am still thinking that maybe what i did last night actually worked,
and maybe i just did not wait long enough fro dhcp-1 to come out of
recovery=wait because the mclt time was 30 mins.
I was also thinking to simply shut down dhcpd on both servers, delete
the dhcpd.leases files on both servers, then start up dhcp-2, then
dhcp-1 and hopefully they would be in sync faster? Or even maybe
decrease the mclt time from 30 mins to 5 mins? not sure what that would
do? Our leases times are 20 minutes. and at 3AM est, not many people
should care if they loose their IP for 20 mins, i hope...
On 2016-02-10 12:27 PM, Niall O'Reilly wrote:
> On 10 Feb 2016, at 16:36, Rob Morin wrote:
>> Currently dhcp-1 daemon is not running, dhcp-2 is running and giving
>> out leases just fine, but in "stand alone" mode, meaning failover is
>> not configured.
> At least that's good!
>> What i need to do is re-config dhcp-2 to be the secondary in a
>> failover mode,
> How important is it that dhcp-2 be the secondary, and not the primary?
> [Pas besoin de me répondre: c'est un point de réflexion]
>> which would be just commentating the line in the dhcpd.conf file that
>> tells it that ir is the secondary, and then add dhcp-1 to the mix.
> It might be simpler to introduce dhcp-1 as secondary.
> If it's not acceptable to keep the servers in this "reversed"
> I'ld suggest the sequence outlines below. It's tedious, but avoids
> the solo/secondary
> transition which (a) scares me and (b) seems to be giving you trouble.
> I've done this kind of juggling, but long enough ago that I don't
> remember enough
> detail to give you a tested worked example. Besides, I don't work
> there any more
> and so no longer have access to the boxes.
> Initial condition: dhcp-2 in "solo" (less typing than "stand
> alone"!) mode
> Ensure dhcp-1 is running the same version of the server code as dhcp-2
> Prepare dhcp-2 to be primary and dhcp-1 to be secondary
> Enable failover and wait until stable operating conditions are
> Note: this failover phase is simply a preparation for migrating to
> "solo" mode on dhcp-1
> Disable dhcp-2 and set dhcp-1 in "partner-down" mode
> Prepare dhcp-1 for "solo" operation and then restart it
> You should at this stage have the same situation as now, but with
> dhcp-1 in "solo" mode.
> Finally, prepare the target failover configuration (with dhcp-1 as
> primary) on each node
> and activate when ready.
> I'm not entirely sure that it will, but I hope this helps.
> Best regards,
> Niall O'Reilly
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