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Old 07-29-2010, 12:29 PM
Phil Manuel
 
Default DHCP failover ... Some questions.

On 29/07/10 9:55 PM, Götz Reinicke - IT-Koordinator wrote:
> Hi,
>
> I plan to reorganise our IP management and I'd like to implement a slave
> DHCP server. Right now we assign IP addresses based on the
> ethernetadress of a client 1:1.
>
> The tutorial here [1] is simple and looks like the thing I need.
>
> I do have a lot of subnetworks and my cisco router has an DHCP helper
> address set. I know I'll have to add the second dhcp-server address.
>
> My questions now is:
>
> Dose the dhcp-slave syncs the dhcp data from the master?
>
> Or do I have to copy the data to the master AND slave?
>
> Any other sugesstions or comments?
>
>
> Thanks and best regards,
>
> Götz
>
>
Hi,
I thought the latest dhcp server had built-in support for master-slave
scenarios, it just replicates current status to the slave, and when it
fails the slave takes over.

Phil.
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Old 07-29-2010, 12:31 PM
Lars Hecking
 
Default DHCP failover ... Some questions.

G?tz Reinicke - IT-Koordinator writes:
> Hi,
>
> I plan to reorganise our IP management and I'd like to implement a slave
> DHCP server. Right now we assign IP addresses based on the
> ethernetadress of a client 1:1.
>
> The tutorial here [1] is simple and looks like the thing I need.
>
> I do have a lot of subnetworks and my cisco router has an DHCP helper
> address set. I know I'll have to add the second dhcp-server address.
>
> My questions now is:
>
> Dose the dhcp-slave syncs the dhcp data from the master?
>
> Or do I have to copy the data to the master AND slave?
>
> Any other sugesstions or comments?

The servers will balance the pool(s) between them. It's actually fun (for
personal preference values of "fun") to tail the logs on both servers
after starting the slave and watch dhcpd communicate.



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Old 07-29-2010, 01:03 PM
Lars Hecking
 
Default DHCP failover ... Some questions.

>
> > The servers will balance the pool(s) between them. It's actually fun (for
> > personal preference values of "fun") to tail the logs on both servers
> > after starting the slave and watch dhcpd communicate.
>
>
> So they "only" balance the pool and no 1:1 assignment from
> IP:Host-MAC-address.

Sorry, I had to re-read your original posting ...

The best way to set this up is to have a minimal dhcp.conf on both servers
that contains global definitions and the failover section, and then includes
another config file that contains everything else - the shared-network block
with pools, groups etc. This second config file is the same for both servers
and you need to keep it in sync.



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Old 07-29-2010, 06:37 PM
Les Mikesell
 
Default DHCP failover ... Some questions.

On 7/29/2010 8:03 AM, Lars Hecking wrote:
>>
>>> The servers will balance the pool(s) between them. It's actually fun (for
>>> personal preference values of "fun") to tail the logs on both servers
>>> after starting the slave and watch dhcpd communicate.
>>
>>
>> So they "only" balance the pool and no 1:1 assignment from
>> IP:Host-MAC-address.
>
> Sorry, I had to re-read your original posting ...
>
> The best way to set this up is to have a minimal dhcp.conf on both servers
> that contains global definitions and the failover section, and then includes
> another config file that contains everything else - the shared-network block
> with pools, groups etc. This second config file is the same for both servers
> and you need to keep it in sync.

Do you know if you have to do anything special in the case where the
primary server has been down for a while and is then brought back up?
That is, does the backup automatically re-sync the database with the new
leases that have been given out, or does it not have to?

--
Les Mikesell
lesmikesell@gmail.com
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Old 07-29-2010, 08:36 PM
Lars Hecking
 
Default DHCP failover ... Some questions.

> Do you know if you have to do anything special in the case where the
> primary server has been down for a while and is then brought back up?
> That is, does the backup automatically re-sync the database with the new
> leases that have been given out, or does it not have to?

Nope, it's all automatic - that's the point, after all

Check out the FAILOVER STARTUP section in dhcpd.conf(5).



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Old 07-30-2010, 03:17 PM
Les Mikesell
 
Default DHCP failover ... Some questions.

On 7/29/2010 3:36 PM, Lars Hecking wrote:
>
>> Do you know if you have to do anything special in the case where the
>> primary server has been down for a while and is then brought back up?
>> That is, does the backup automatically re-sync the database with the new
>> leases that have been given out, or does it not have to?
>
> Nope, it's all automatic - that's the point, after all
>
> Check out the FAILOVER STARTUP section in dhcpd.conf(5).

OK, I can confirm it works. I had been putting off changing my dhcp
service for years because the last time I changed it a lot of clients
(back in Win95/98 days) didn't switch gracefully and the old dhcp server
never had downtime. But, this time everything still seems happy and
will accept the ack to continue a lease from either of the new failover
servers.

--
Les Mikesell
lesmikesell@gmail.com


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