High ram-usage with multiple /16 ipv4 networks

Ruben Wisniewski ruben at freifunk-nrw.de
Mon Apr 27 14:46:41 UTC 2015

Am Tue, 21 Apr 2015 14:33:21 +0200
schrieb Peter Rathlev <peter at rathlev.dk>:

> On Tue, 2015-04-21 at 13:18 +0200, Ruben Wisniewski wrote:
> > When I delete the "deny all clients" rules, the ram-footage is
> > reduced to 35 MByte:
> > 
> > [root at bragi ~]# pmap -x 30521
> > 30521:   /usr/bin/dhcpd -4 -q -pf /run/dhcpd4.pid
> ...
> > kB gesamt          34608   28792   26292
> > 
> > So where can I file this bug?
> Umm... what bug? :-)
> With 1.5 million leases you use 533 Mbytes memory, with just 2558
> leases you use 35 Mbytes memory. That's not a bug.
> What you want sounds like some way of actively denying clients with
> specific addresses without creating leases for them. I can't from the
> top of my head think of such a way with ISC DHCP, but I'll give it a
> try.

I think a pool which got "deny all clients" should be optimised for not
using the whole memory for nothing... since the leases will never been

Else I wonder why an authorative server not answering all requests from
a subnet.

The man-page says this:

>If the server knows nothing about the address, it will remain silent,
>unless the address is incorrect for the network segment to which the
>client has been attached and the server is authoritative for that
>network segment, in which case the server will send a DHCPNAK even
>though it doesn't know about the address.

Network-segment seem to be the pool-definition here, not the subnet.
Wondering if this is correct or a bug.

Best regards

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