Re: High ram-usage with multiple /16 ipv4 networks

Posted by Simon Hobson on Apr 20, 2015; 6:50pm
URL: http://isc-dhcp-users.193.s1.nabble.com/High-ram-usage-with-multiple-16-ipv4-networks-tp41p43.html

Peter Rathlev <[hidden email]> wrote:

> Hmm... I'm not sure I understand the configuration:
>
> On Mon, 2015-04-20 at 17:14 +0200, Ruben Wisniewski wrote:
>> subnet 10.66.0.0 netmask 255.255.0.0 {
>>    range 10.66.11.1 10.66.20.255; #main
>>    pool {
>>        range 10.66.1.1 10.66.10.255;
>>        deny all clients;
>>    }
>>    pool {
>>        range 10.66.30.1 10.66.254.255;
>>        deny all clients;
>>    }
>
> Wouldn't the "deny all clients" statements make those ranges a no-op?

Correct.

> Otherwise it seems to fit with what we see on our servers. I'm guessing
> the ranges that deny all clients still create leases.

Yes, on startup, hash tables are created to hold every address configured - and I'd assume they won't have done a specific test for that "deny everything".
So even if you have few clients, the hash tables can be very large if you define large ranges - not it's the ranges, not the subnets, that need space.



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