Two dhcp servers with same dhcpd.conf (fixed-address hosts)

Gregory Sloop gregs at
Thu Aug 7 14:55:56 UTC 2014

>>> I have a dhcp server with all hosts configured in static mode/fixed-address.
>>> Thus the dhcp failover is not applicable.
>>> I want to create a secondary/slave dhcp server in case the primary server fails.
>>> How to do this?
>>> I can keep the two servers with the same dhcpd.conf working together?

>>> Thanks,

>>> Marcos.

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MRdSJ> It seems to me that the failover is mandatory to use a pool.
MRdSJ> For dynamic addresses ok, but all my addresses are fixed.
MRdSJ> In fact the use of a pool in this case leave me a little confused.
MRdSJ> As would be the setting for this case, where all addresses are fixed, 
MRdSJ> how would you define the pool?

If you're using *all* fixed addresses, you don't use a pool, and shouldn't have one.

Perhaps you might post your proposed config, if you still have questions - but read the docs carefully. 

Even if you have *both* dynamic and fixed addresses - the fixed ones should not also exist inside a pool. [However, you'd need a fail-over setup in this situation.]
There are quite a number of conditions, which you might not have considered, that will mean a "fixed" address will get handed out as a dynamic to a client you didn't intend to get it. If the fixed address is NOT listed in a pool, that can't happen, and the server will still be able to give it out to the assigned host.

** tldr; Fixed host addresses assignments do NOT need to be in a pool to allow the dhcpd server to hand them out, and in fact, should not be listed in any pool. If they are listed in the pool, unexpected things may happen. 

[It may work fine, in practice, too, depending on your situation. But it's a bad practice, and will only end up potentially hurting you, never benefiting you.]

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