how to test the scalibity and stabilty of ISC DHCP???

Michal Suchanek hramrach at
Wed Dec 7 11:15:25 UTC 2011


On 7 December 2011 00:50, Chris Buxton <chris.p.buxton at> wrote:
> I have a similar, but slightly more detailed, question.
> How can I calculate how much memory a DHCP server will require, based on the number of addresses and also on the number of failover relationships? I have a client who wants to use several dozen failover relationships (hub and spoke, ~30 spokes) supporting around 35K leases, on a budget box (1 GB memory, small-ish hard drive, 1000 Mbit network).
> Does anyone think that will work? Or that it won't work? I'm inclined to think he needs a bigger box as the hub, but I don't have any data to back that up.

Easiest: make the data. If you are going to buy 30 boxes the cost of
buying one more and leaving it as spare if it does not work as the hub
is not that bad. Also the memory and hardrive can be replaced in most
systems so you can likely just upgrade it anyway.

If you want something really fast you can use a SSD for drive, those
are not that expensive anymore and something like 40G is more than
enough to hold a system and 35k leases.

I don't think 1G ram is that small, though. It gives 29M ram per lease.



> Regards,
> Chris
> On Dec 5, 2011, at 12:00 AM, Simon Hobson wrote:
>> ameen.shajahan at wrote:
>>>                Also how many dhcp entries can ISC DHCP code would support?
>> AFAIK, that is entirely dependent on your hardware. I believe there are users with many 10s of thousands of users.
>> CPU capacity is rarely a limit.
>> You need memory to store the in memory tables and hashes - basically the more available IPs in pools, the more memory you need. This is (IIRC) largely independent of how many of those addresses are actually leased.
>> And then you disk I/O performance to handle the updates. Firstly to update the leases file, secondly to handle the logging. This appears to be the main constraint people hit.
>> In terms of testing performance, there are some stress testing tools around - hopefully someone will pop up and suggest which to use.
>> --
>> Simon Hobson
>> Visit for books by acclaimed
>> author Gladys Hobson. Novels - poetry - short stories - ideal as
>> Christmas stocking fillers. Some available as e-books.
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