[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
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:
>> 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?
>> Dnsmasq-discuss mailing list
>> Dnsmasq-discuss at lists.thekelleys.org.uk
> Dnsmasq-discuss mailing list
> Dnsmasq-discuss at lists.thekelleys.org.uk
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