address range ... not on net

Simon Hobson dhcp1 at thehobsons.co.uk
Wed Jul 2 18:09:50 UTC 2008


Benjamin Wiechman wrote:

>In the case of a shared network as described, how does the dhcp server
>determine which subnet to use when assigning an address? If I would have two
>subnets would it default to one until filled, then assign addresses from the
>second or would I need to use classes or some other mechanism to assign
>clients to one subnet or the other?

It is 'undefined' - ie in a shared network, unless you tell the 
server otherwise then it assumes all addresses are equal and it can 
give any available address to any client. In practice there is an 
order due to the (undocumented and liable to change without notice) 
internal mechanism the server uses, this being to allocate addresses 
'top down'.

If you wish to have certain clients in a particular subnet then you 
must tell the server how to do it with appropriate allow and deny 
clauses in the pools. The criteria can be something basic like 
'known' or 'unknown', but is more usually done via classes.


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