Scalability million addresses

Glenn Satchell Glenn.Satchell at
Thu Nov 12 00:23:30 UTC 2009

The other issue with such a high number of clients is mitigating or
managing the risk factor. Obviously there are a very large number of
clients. Should you run the risk of having a central, single point of
failure? Even a pair of dhcp servers running failover is not giving you
much room for failure, error, or even network issues, etc.


>Date: Thu, 12 Nov 2009 00:49:47 +0100
>From: Christoph Weber-Fahr <cwf-ml at>
>To: Users of ISC DHCP <dhcp-users at>
>Subject: Re: Scalability million addresses
>> Got a customer who wants to use DHCP.
>> Would ISC DHCP be able to handle 2 million defined IP addresses with
>> 500K active leases? What would be area of concern (bottlenecks etc)?
>> Thanks
>Not without some serious hacking.
>Unfortunately, ISC DHCPd is very bad at administering large address
>We did some intensive testing with those kinds of loads (pools of up
>to a million addresses), and the results weren't pretty.
>And that is not a problem of active leases - the absolute pool size
>is the the performance relevant number.
>For the moment we settled down on using several geographically
>distributed(redundant pairs) of dhcpds for not more than 90k
>addresses and do not expect such a pair to withstand a sustained
>load of more than 60 qps.
>With a singular (non redundant) system you'd probably get more in
>the area of 200+ k addresses and ~100-150 qps.
>Target hardware were vanilla HP servers wth Xeon 5150
>Those numbers are admittedly a little on the conservative side,
>but not that much.
>We had someone profile that thing for us under load, and
>apparently ISC dhcpd spends most of the time happily
>micromanaging/sorting the whole address pool.
>(BTW - if any of the ISC guys wants our load test
>software capable of simulating that amount of devices,
>I'd be happy to provide it)
>Caveat - those tests were done on versions of dhcpd 3.0 and 3.1,
>I have no data yet on 4.x.
>Christoph Weber-Fahr
>dhcp-users mailing list
>dhcp-users at

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