matt at smarterbroadband.net
Wed Dec 1 22:14:21 UTC 2010
Would it be possible to have a distributed NFS directory and have many
dhcp daemons read the same leases and configuration files? Does the DHCP
Server re-read the leases file when it starts up so it knows about all
On 11/30/2010 02:21 AM, Simon Hobson wrote:
> Matt Jenkins wrote:
>> So is it possible to maintain a central or distributed leases file
>> for multiple (unknown quantity) of servers?
>> I ask because I am working on a design to change over all of my
>> wireless clients to dhcp. With the wide spread nature of the network,
>> ALL services are distributed so that any single point can fail and
>> everything else stays active. This assumes that the point of failure
>> will never recover. The system MUST be able to handle this
>> automatically. I definitely do not have 2x the address space as
>> others suggested. I kind of assumed that the dhcp servers maintained
>> synchronised information regarding leases.
>> I estimate the need for 17 dhcp servers (right now) distributed
>> across the system handling multiple /18's (in total) of address
>> space. Can this be handled?
> Failover is only supported between two servers, but you can have
> different pairings for different subnets. Eg, you can have A&B for one
> subnet, A&C for another, A&D for another, C&E for another - whatever
> you want.
> I think you can do this by pools, but that sounds like a recipe for
> confusion myself !
> In your situation, a hub and spoke arrangement might make sense (it
> depends to a certain extent on your network topology). Have one
> central DHCP server that serves all networks, and a partner for each
> Obviously the central server will need to be big enough to handle all
> the traffic, but each satellite system can be much smaller.
> There was an interesting idea put up a while ago (that was in the
> context of an ISP setup). In that suggestion, the remotes could keep
> their lease database in a ram disk - good for performance on a low
> spec machine. Should the remote site have a power failure, then on
> startup, the DHCP server can load it's lease database from the central
> server. Obviously, since the central machine is the only one with
> non-volatile storage, then it will need to be reasonably reliable (not
> too hard with server grade hardware).
> As already said, if you wish to do so, then you can script your own
> checks to detect a partner failure, and automatically put the
> remaining server into partner down state. What checks you do is up to
> you - it's your network and only you will have the knowledge to
> differentiate between failure modes and determine if "can't talk to
> remote server" really means that it is either down or at least unable
> to communicate with clients.
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