performance with 20000 classes; release a lease manually

Simon Hobson dhcp1 at
Wed May 27 18:05:16 UTC 2009

stefan novak wrote:

>My config is very simple and works as expected.
>The client behind the cable modem always gets the fixed address. is
>this config scaleable to 20000 classes, or is there another way to
>configure such a scenario.

Dunno, but there was a similar thread here a week or two ago that 
might be worth looking through.

>My secound question is about the file. is it possible to
>release an already taken lease?
>that if the client behind the cable modem changes, the ip is assigned
>to the new client. is that possible?

I suspect the easiest way would be to knock up a script that 
generates a fake DHCP Release message that appears to come from the 

Other than that, OMAPI is the way to modify leases with the server 
running - but it's not something I've ever used myself.

>class "customer1" {
>          match if binary-to-ascii(16, 8, ":",  option agent.remote-id
>) = "0:1e:69:ef:8e:b5"; # <- Modem Mac
>          lease limit 1;

You could increase performance by removing the binary-to-ascii step. 
As you scale up, all these conversions will add up - and EVERY single 
one has to be executed each time a request comes in.

I think :
  match if binary-to-ascii(16, 8, ":",  option agent.remote-id) = 

is equivalent to :
  match if option agent.remote-id = \00\1e\69\ef\8e\b5 ;

Simon Hobson

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