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Today's Topics:
1. Re: Migrating dhcpd from a "single" server to "failover peer"
setup (Simon Hobson)
2. Re: Recommendation for redundancy (Simon Hobson)
3. Re: Recommendation for redundancy (Bob Harold)
4. Re: Migrating dhcpd from a "single" server to "failover peer"
setup (Danny Kulchinsky)
5. Re: Recommendation for redundancy (Tiago SR)
6. Re: Recommendation for redundancy (Pereida, Alejandro)
7. Re: Recommendation for redundancy (Simon Hobson)
----------------------------------------------------------------------
Message: 1
Date: Tue, 6 Mar 2018 13:07:08 +0000
From: Simon Hobson <dh...@thehobsons.co.uk>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: Migrating dhcpd from a "single" server to "failover peer"
setup
Message-ID: <78b0ad80-cfa3-4acd-abb2-a09aa2e89...@thehobsons.co.uk>
Content-Type: text/plain; charset=us-ascii
Danny Kulchinsky <danny....@gmail.com> wrote:
> It is not very clear to me what would be the imapct of adding the failover
> peer configuration into an exisiting systems with leases that we obvisouly
> can't lose, I'm hoping that the system will perform the necessary changes but
> I don't feel confident about this.
Yes, you just need to add the failover setup and the servers will automagically
sync the existing leases to the new server. AIUI, the existing active leases
will be "owned" by the original server, and any free addresses will be shared
between the two servers.
> Also, our ranges are defined under subnet and it is my understanding that
> these should be defined under pools where the "failover peer" is to be
> configured, is that correct? so, I guess same question here - can we move the
> ranges to "pools" without affecting any of the lease data?
Yes.
------------------------------
Message: 2
Date: Tue, 6 Mar 2018 13:13:26 +0000
From: Simon Hobson <dh...@thehobsons.co.uk>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: Recommendation for redundancy
Message-ID: <95b48ce6-71a5-458b-bb4e-ccca22f39...@thehobsons.co.uk>
Content-Type: text/plain; charset=windows-1252
"Pereida, Alejandro" <apere...@iid.com> wrote:
> We have been using a single Linux server as our DHCP server running ISC DHCP
> Server 4.3.1
> We are building a ?secondary datacenter? for disaster recovery purposes. What
> is the most recommended
> Option for implementing a redundant DHCP server scenario in case the main
> datacenter (where the DHCP server resides)
> goes dark?
You need to expand a bit - is this to support the existing addresses, or
another range, or something else ? And are the sites permanently networked
together ?
In principle, all you need to do is add another server in a failover pair - and
then both servers will support the same address range(s). Given the additional
hop, it's likely that the on-site server will handle requests most of the time
as it'll get a reply back to the clients first.
------------------------------
Message: 3
Date: Tue, 6 Mar 2018 09:18:47 -0500
From: Bob Harold <rharo...@umich.edu>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: Recommendation for redundancy
Message-ID:
<ca+nkc8b92cpjqgqjaxfdazr9ngpqd8ln-aavkw2b5jvzvak...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
On Tue, Mar 6, 2018 at 8:13 AM, Simon Hobson <dh...@thehobsons.co.uk> wrote:
> "Pereida, Alejandro" <apere...@iid.com> wrote:
>
> > We have been using a single Linux server as our DHCP server running ISC
> DHCP Server 4.3.1
> > We are building a ?secondary datacenter? for disaster recovery purposes.
> What is the most recommended
> > Option for implementing a redundant DHCP server scenario in case the
> main datacenter (where the DHCP server resides)
> > goes dark?
>
> You need to expand a bit - is this to support the existing addresses, or
> another range, or something else ? And are the sites permanently networked
> together ?
>
> In principle, all you need to do is add another server in a failover pair
> - and then both servers will support the same address range(s). Given the
> additional hop, it's likely that the on-site server will handle requests
> most of the time as it'll get a reply back to the clients first.
>
>
The two servers will share the load, unless you change "split", "hba", or
"load balance max seconds". Setting "split" to 255 is probably what you
want if you want the primary server to answer everyone, and the failover to
only answer if the primary is unreachable.
https://kb.isc.org/article/AA-00502/0/A-Basic-Guide-to-Configuring-DHCP-Failover.html
--
Bob Harold
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Message: 4
Date: Tue, 6 Mar 2018 09:26:43 -0500
From: Danny Kulchinsky <danny....@gmail.com>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: Migrating dhcpd from a "single" server to "failover peer"
setup
Message-ID:
<cacrqnspi8spn7gnmpaq60ukixgm4tp-tu1n8epbrwgh6jnr...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Thank you Simon, this is very encouraging!
We are going to start by moving the ranges into pools and next step would
be to establish the failover peer.
If you have any tips, let me know :)
Regards,
Danny
On 6 March 2018 at 08:07, Simon Hobson <dh...@thehobsons.co.uk> wrote:
> Danny Kulchinsky <danny....@gmail.com> wrote:
>
> > It is not very clear to me what would be the imapct of adding the
> failover peer configuration into an exisiting systems with leases that we
> obvisouly can't lose, I'm hoping that the system will perform the necessary
> changes but I don't feel confident about this.
>
> Yes, you just need to add the failover setup and the servers will
> automagically sync the existing leases to the new server. AIUI, the
> existing active leases will be "owned" by the original server, and any free
> addresses will be shared between the two servers.
>
> > Also, our ranges are defined under subnet and it is my understanding
> that these should be defined under pools where the "failover peer" is to be
> configured, is that correct? so, I guess same question here - can we move
> the ranges to "pools" without affecting any of the lease data?
>
> Yes.
>
> _______________________________________________
> dhcp-users mailing list
> dhcp-users@lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users
>
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------------------------------
Message: 5
Date: Tue, 06 Mar 2018 12:47:41 -0300
From: Tiago SR <lis...@tiagosr.com>
To: "Users of ISC DHCP" <dhcp-users@lists.isc.org>
Subject: Re: Recommendation for redundancy
Message-ID:
<161fbff31b3.dbf7f175409891.1909039225645594...@tiagosr.com>
Content-Type: text/plain; charset="UTF-8"
If you make use of DHCP Relay or can implement it, you could get the servers
failover by VRRP, IP SLA, OSPF, etc.
The DHCP Relay would query a DHCP Server IP address that would automatically
point to secondary server in case of primary going down.
---- On Mon, 05 Mar 2018 20:20:50 -0300 Pereida, Alejandro <apere...@iid.com>
wrote ----
> Hello all:
>
> We have been using a single Linux server as our DHCP server running ISC
> DHCP Server 4.3.1
> We are building a ?secondary datacenter? for disaster recovery purposes.
> What is the most recommended
> Option for implementing a redundant DHCP server scenario in case the main
> datacenter (where the DHCP server resides)
> goes dark?
>
> Thanks in advance
>
> Alex Pereida
> _______________________________________________
> dhcp-users mailing list
> dhcp-users@lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users
>
------------------------------
Message: 6
Date: Tue, 6 Mar 2018 16:07:01 +0000
From: "Pereida, Alejandro" <apere...@iid.com>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: Recommendation for redundancy
Message-ID: <d6c3fc51.366df%apere...@iid.com>
Content-Type: text/plain; charset="iso-8859-1"
We would like redundancy to support the existing addresses (about 80
address pools), yes both the active Datacenter and DR center are
permanently tied
Together via a redundant 10Gb fiber link
On 3/6/18, 5:13 AM, "dhcp-users on behalf of Simon Hobson"
<dhcp-users-boun...@lists.isc.org on behalf of dh...@thehobsons.co.uk>
wrote:
>"Pereida, Alejandro" <apere...@iid.com> wrote:
>
>> We have been using a single Linux server as our DHCP server running ISC
>>DHCP Server 4.3.1
>> We are building a ?secondary datacenter? for disaster recovery
>>purposes. What is the most recommended
>> Option for implementing a redundant DHCP server scenario in case the
>>main datacenter (where the DHCP server resides)
>> goes dark?
>
>You need to expand a bit - is this to support the existing addresses, or
>another range, or something else ? And are the sites permanently
>networked together ?
>
>In principle, all you need to do is add another server in a failover pair
>- and then both servers will support the same address range(s). Given the
>additional hop, it's likely that the on-site server will handle requests
>most of the time as it'll get a reply back to the clients first.
>
>_______________________________________________
>dhcp-users mailing list
>dhcp-users@lists.isc.org
>https://lists.isc.org/mailman/listinfo/dhcp-users
------------------------------
Message: 7
Date: Tue, 6 Mar 2018 19:08:25 +0000
From: Simon Hobson <dh...@thehobsons.co.uk>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: Recommendation for redundancy
Message-ID: <f7159e3c-ae2b-4cd1-9b45-49671725e...@thehobsons.co.uk>
Content-Type: text/plain; charset=us-ascii
Tiago SR <lis...@tiagosr.com> wrote:
> If you make use of DHCP Relay or can implement it, you could get the servers
> failover by VRRP, IP SLA, OSPF, etc.
> The DHCP Relay would query a DHCP Server IP address that would automatically
> point to secondary server in case of primary going down.
The problem with that is that unless you use the failover protocol then you
cannot easily have a seamless handover - this is NOT a stateless server like a
web server serving static pages. The standby server must AT ALL TIMES have a
completer and up to date copy of what the master server has - that is not easy
to do without using failover. If the backup server does not have a complete and
accurate copy of the primary server's lease database then you will suffer from
one or more potentially serious problems.
Once you use failover to manage syncing the leases to the backup, then you
might as well just use failover to manage availability.
------------------------------
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