How does DHCPD determine what IP address to assign and...

[Ryan McCain]

I found a few posts in the archives but am a bit confused.  I don't know what the 0 and 9 are for and used the example I found as a template.  I am on the right track if I want all DHCP clients that connect w/ the UID containing ASYNC be assigned IP addresses between 10.120.5.100-108 only??


class "DialUp" {
    match if substring(option vendor-class-identifier, 0, 9) = "ASYNC";
        log (info, " Matched Dialup Rule");
        range 10.120.5.100 10.120.5.108
}

..Thanks..

>>> On Fri, Dec 21, 2007 at 12:40 PM, in message
<a06240822c391b86b364d at simon.thehobsons.co.uk>, Simon Hobson
<dhcp1 at thehobsons.co.uk> wrote: 
> Ryan McCain wrote:
> 
>>1) If I have a defined scope of 10.120.5.1 - 10.120.5.180, whill 
>>DHCPD hand out .1 to the first DHCPD client, .2 to the second and so 
>>on?  Or is there another algorithm thats used?
> 
> No, officially the initial order is undefined - in practice, the 
> current implementation will allocate unused leases from the highest 
> address down for no other reason than the way they are hashed 
> internally.
> 
> Once there are no "never used before" addresses left, addresses are 
> recovered from expired leases on a least recently used basis.
> 
>>2) Is it possible to assign a subset of IP addresses in my scope to 
>>DHCP clients whos UID identifier contains a specific string?  For 
>>example, all dialup users have ASYNC in their UID.  We'd like to be 
>>able to assign them IP addresses 10.120.5.100 - .180.
> 
> Yes, see the list archives, and 'man dhcpd.conf' looking for classes 
> and subclasses.
> 
> Very briefly, you define a class which matches on some criteria (such 
> as the UID starting with ASYNC), then define a pool and only allow 
> members of the class to use that pool.