[Dnsmasq-discuss] Redundant setup with Dnsmasq

richardvoigt at gmail.com richardvoigt at gmail.com
Thu Dec 22 18:58:32 GMT 2011


On Thu, Dec 22, 2011 at 8:13 AM, Michael Rack
<michael.rack at rsm-freilassing.de> wrote:
> Very easy.
>
> You need at least one virtual ip-address for your DNS- and DHCP-Server.
>
> So lets say you have a Class-C Network 10.0.0.0/24
>
>     * Primary DNS / DHCP    10.0.0.251
>     * Secondary DNS / DHCP  10.0.0.252
>
> Now, you add a virtual IP to your primary DNS - lets say
>
>     * Virtual-IP            10.0.0.250
>
>  From Secondary you create a Bash-Script that do the following:
>
>     * Check the Server-Status by ping the virtual ip-address
>     * when the ping has failed:
>        * add the virtual ip-address to your network-configuration
>        * start dnsmasq
>
> To sync the DHCP-Leases to the secondary server, you need to create a
> ssh-key (ssh-keygen) to copy the lease-file without knowing the ssh-passord.
>
> scp 10.0.0.251:/var/dhcp/dnsmasq.leases /var/dhcp/dnsmasq.leases

Please note that by default, automatic DNS registrations and the list
of existing DHCP leases are going to be lost during failover.

Copying the dnsmasq.leases file with cron creates a race condition as
it is not synchronized with dnsmasq updating the file.  I would
recommend using a external database to store the leases with support
for atomic updates instead  of letting dnsmasq put them in
/var/*/dnsmasq.leases.

See the dhcp-script and leasefile-ro options.



>
> do this every minute via a crontab.
>
> So, thats it.
>
>
> Liebe Grüße aus Freilassing,
>
> Michael Rack
> RSM Freilassing
> --
> RSM Freilassing                 Tel.: +49 8654 607110
> Nocksteinstr. 13                Fax.: +49 8654 670438
> D-83395 Freilassing            www.rsm-freilassing.de
>
>
> Am 22.12.2011 14:16, schrieb Markus Schöpflin:
>> Hello,
>>
>> up to now I have been using Dnsmasq with great success in a medium sized setup
>> as a DNS/DHCP/TFTP server in a private test bed. It currently serves a few
>> hundred clients (mostly servers and networking equipment) in four different LANs.
>>
>> A few of the clients have statically configured IP addresses but most are
>> using DHCP with automatic DNS registration.
>>
>> Now I'm faced with the need to create a fault tolerant setup for DHCP and DNS.
>> I need at least some kind of backup service for DHCP and DNS which takes over
>> automatically as soon as the primary server fails. Is this kind of setup
>> supported somehow with Dnsmasq? Or should I be looking into migrating to the
>> ISC DHCP server and the Bind DNS server for this?
>>
>> Regards,
>> Markus
>>
>>
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>
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