Failover and pools with single machines

Simon Hobson dhcp1 at
Thu Dec 14 15:52:24 UTC 2006

Tina Siegenthaler wrote:

>  > Failover won't work with such small pools. However, since you will
>>  only have one client/pool then you could simply replicate the config
>>  and NOT use failover. The client will get the same address regardless
>>  of which server it took the lease from, and no other client will get
>>  the same address from the other server.
>>  You would still need to use failover on the general use pools though.

>Does this mean I can just use the same config file (or that part of 
>it with the single-host pools) on 2 dhcp servers at the same time? 
>Won't they get each other in the way?

Ordinarily, having two independent servers offering the same 
addresses would be a disaster looking for somewhere to happen. It 
will work in this case because you have pools with exactly one 
address which can be leased to exactly one client - so you can't have 
the same address offered to two different clients.

>So, if I understand this
>correctly, a host will issue a broadcast and then take the IP address 
>from the first dhcp server that responds. And it doesn't matter if 
>there is a second dhcp server which would also be able to assign the 
>host an address, since it's already got one. Right?

Near enough - technically the client is allowed to see what offers it 
gets and choose between them (how is not defined, but for example it 
could choose the one that gives it the most options it asked for). In 
practice, I don't think anyone has found a client that doesn't just 
accept the first offer !

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