DHCP + mysql

jgomez at infoweapons.com jgomez at infoweapons.com
Mon Mar 19 07:37:42 UTC 2007

Mr. Hobson,

Thank you soo much for the information ;)


> jgomez at infoweapons.com wrote:
>>Is it possible to use mysql or any database applications instead of
>>dhcpd.leases in keeping a persistent database of leases that has assigned
>>to clients.?
> Technically, yes; in practice, no.
> AFAIK the ISC server does not have the capability to do this, and I
> seriously doubt that they would be interested in adding it. There are
> two main reasons :
> 1) Performance.
> Appending to a log file is a fast operation, which means you can
> service clients quickly. Updating an SQL database is going to be VERY
> much slower and that would impinge on the ability of the server to
> service client requests in a timely manner. The current server is, I
> believe, single threaded - so if you introduce even a small delay
> into each transaction then you severely restrict the volume of
> transactions you can handle. Internally the ISC server keeps the data
> in hashed lists for quick searching, no SQL database is going to
> match that for query speed.
> 2) Security
> It is a requirement of the rfc that all leases must be written to
> permanent store before being offered to a client - thus avoiding the
> possible situation where a lease is offered, the server dies for
> whatever reason, and then the server offers the same lease to another
> client because it doesn't know about the first offer. Again, this is
> very quick for a log file, but quite slow for an SQL database -
> especially when you consider that you must sync a consistent database
> to disk after each and every update. NB - this requirement is one of
> those that is ignored by most other servers, including Microsofts.
> Even if you got around these two problems, ISC do not have
> development staff sitting around looking for things to do and so are
> unlikely to want to put the amount of effort required into what is
> probably a minority feature.

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