failover timeout

Glenn Satchell glenn.satchell at
Fri Apr 9 04:29:54 UTC 2010

200k leases with one week duration. One week is 604800 seconds, so 200k 
leases renewing weekly would be about one every 3 seconds. Even if 
clients renew more often (typically 50% of lease time, or customers 
reboot CPE) this is still a very low number that would not require a 
very powerful computer. Given the high number of clients, failover or HA 
of some sort would be a good recommendation.


On 04/09/10 00:39, Glenn Satchell wrote:
> 4,2.0 (currently alpha) has a configurable auto-partner-down feature.
> For all earlier releases the server stays in communications-interrupted
> and *never* goes to partner down mode without manual action.
> Partner-down is the mode where the surviving server can allocate
> addresses previously given out by the failed server.
> Having said that it is pretty easy to write a script that monitors the
> other dhcp server, and uses omshell to switch to partner down when it
> detects that the other server has gone away. When the failed server
> comes back it will come out of partner-down mode and return to normal as
> part of the startup negotiations.
> There was a post to the list by David Hankins on 25 Feb this year
> mentioning this which gives a lot more detail.
> regards,
> -glenn
> On 04/08/10 13:48, Abu Abdulla alhanbali wrote:
>> this is not what i mean. if the primary servers is down, how long will
>> it take the secondary server to start assigning the IPs that are
>> reserved for the primary server. you can do this manually using the
>> omshell but i don't know if this will be done automatically or not.
>> On Wed, Apr 7, 2010 at 7:55 PM, Banana Flex<flex.banana at>
>> wrote:
>>> hi
>>> you can do a collaboration betwen two servers that send the same
>>> subnet, see the man page of dhcpd.conf for many information. you can
>>> also configure the timeout. 3 seconds is a good choice
>>> have fun
>>> Banana
>>> On Apr 7, 2010, at 5:41 AM, Abu Abdulla alhanbali wrote:
>>>> Hi,
>>>> i would like to know how long it will take the secondary DHCP server
>>>> to start assigning IPs for all users (including the ranges dedicated
>>>> to the primary) in case the primary DHCP is down? is it a
>>>> configurable?
>>>> i would like also to ask if the DHCP can handle 200K users or above
>>>> assuming the H/W is capable and the lease time is big enough (more
>>>> than one week). is it recommended to run multiple instances or let one
>>>> instance handle this number.
>>>> thanks
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Glenn Satchell                            |  Miss 9: What do you
Uniq Advances Pty Ltd, Sydney Australia   |  do at work Dad?
mailto:glenn.satchell at         |  Miss 6: He just tel:0409-458-580   |  types random stuff.

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