dhcp-users Digest, Vol 165, Issue 6

Fri Jul 15 16:16:36 UTC 2022

> On 15 Jul 2022, at 16.26, Ryan Shea <ryan at muppethouse.com> wrote:
> 
> Ahh, so I'm not a unique snowflake. I did actually already separate out the static host definitions into a separate file. My process for updating the file (which is a somewhat frequent operation) is
> update one of the files
> test the config `dhcpd -t -cf dhcpd.conf`
> reload the daemon
> scp to the secondary
> reload the daemon
> hope that you don't miss any of these steps
You may keep them in a separate file included in the .conf.

So edit the host file
reload 1
Check for errors - fix if needed
transfer file
reload 2
Done

If the file only has host reservations, it will have so fixed structure that any mistake will stick out.

You could also use one of the management systems available.

Dhcpd can AFIK also be used with a database backend with those possibilities.

> Let's compare this to our friends running an active-directory integrated built-in Windows DHCP server. 
> They clickity click on a thing to add a new reservation.
> There is no step 2
> I suppose my take-away is that this is not a user journey I should expect dhcpd to be helpful with. If we're off in roll-your-own territory, I was thinking that using Syncthing to keep the configs automatically in sync, along with some manner of cron job or inotifywait to trigger the secondary to reload would probably work fine. To me, this seems such a common operational pattern that making everyone do their own dental work seems not so terrific - but yes I can come up with something that can work better than manual tomfoolery.
> 
> On Fri, Jul 15, 2022 at 8:05 AM <dhcp-users-request at lists.isc.org <mailto:dhcp-users-request at lists.isc.org>> wrote:
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> Today's Topics:
> 
>    1. Failover + Static host definitions (Ryan Shea)
>    2. Re: Failover + Static host definitions (Richard L. Hamilton)
>    3. Re: Failover + Static host definitions (Glenn Satchell)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Thu, 14 Jul 2022 10:51:04 -0400
> From: Ryan Shea <ryan at muppethouse.com <mailto:ryan at muppethouse.com>>
> To: dhcp-users at lists.isc.org <mailto:dhcp-users at lists.isc.org>
> Subject: Failover + Static host definitions
> Message-ID:
>         <CAL6QW496AknMABKu2874L=MSWvWp_Q9THoUm8QLQnnOjPhO=TQ at mail.gmail.com <mailto:TQ at mail.gmail.com>>
> Content-Type: text/plain; charset="utf-8"
> 
> Failover of a pool seems straightforward enough - however this is
> insufficient in the case where static reservations are present in host
> definitions. I am looking for some solution by which I have a redundant
> pair of dhcpd services which can not only fail over leases from a pool, but
> also keep those hosts with static reservations working.
> 
> Is this as simple as synchronizing the host config definitions and running
> both services - without any particular concern about which server replies?
> Manually managing host configs for reservations in two places seems
> sub-optimal.
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> ------------------------------
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> Message: 2
> Date: Thu, 14 Jul 2022 11:22:13 -0400
> From: "Richard L. Hamilton" <rlhamil at smart.net <mailto:rlhamil at smart.net>>
> To: Users of ISC DHCP <dhcp-users at lists.isc.org <mailto:dhcp-users at lists.isc.org>>
> Subject: Re: Failover + Static host definitions
> Message-ID: <29780D6E-64C1-47CE-9D5C-6094F46B04E1 at smart.net <mailto:29780D6E-64C1-47CE-9D5C-6094F46B04E1 at smart.net>>
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> 
> I have failover set up, and while I have a dynamic range, all known devices have static reservations configured.
> 
> Except for what has to be different between primary and secondary, the configuration files are the same; they both have the same host definitions.
> 
> Separating the configuration file into two parts: the main part with the primary or secondary information and pool definitions, which then includes on both an identical copy of  the file with the static host information, seems like it would simplify matters; you?d only be editing one file and copying it (and restarting both DHCP servers, presumably). Or you could script something really kewl with omshell to do both maybe, but if you make a mistake, you mess up both at the same time. At least if you?re editing a file, you can make sure the primary is behaving after restarting it before copying the edited file over to the secondary and restarting it too.
> 
> Putting the included file on a share that both can access would NOT be as good as it sounds, since that?s one more thing that has to be up in the right order, and could break.
> 
> > On Jul 14, 2022, at 10:51 AM, Ryan Shea <ryan at muppethouse.com <mailto:ryan at muppethouse.com>> wrote:
> > 
> > Failover of a pool seems straightforward enough - however this is insufficient in the case where static reservations are present in host definitions. I am looking for some solution by which I have a redundant pair of dhcpd services which can not only fail over leases from a pool, but also keep those hosts with static reservations working.
> > 
> > Is this as simple as synchronizing the host config definitions and running both services - without any particular concern about which server replies? Manually managing host configs for reservations in two places seems sub-optimal.
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> 
> ------------------------------
> 
> Message: 3
> Date: Fri, 15 Jul 2022 11:04:26 +1000
> From: Glenn Satchell <glenn.satchell at uniq.com.au <mailto:glenn.satchell at uniq.com.au>>
> To: Users of ISC DHCP <dhcp-users at lists.isc.org <mailto:dhcp-users at lists.isc.org>>
> Subject: Re: Failover + Static host definitions
> Message-ID: <305edd76-55db-4ca5-9945-8238ea7449da at email.android.com <mailto:305edd76-55db-4ca5-9945-8238ea7449da at email.android.com>>
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