Host declarations

Alex Moen alexm at
Tue Mar 27 19:17:53 UTC 2007

Hi group,

We're in a situation where we have DSLAMs scattered throughout 5 different
towns.  The relay-agent IP addresses are all on different subnets.  Each
DSLAM has a set of DHCP addresses assigned to the customers on that DSLAM.

However, we would like to use a common pool for customers paying for
DHCP-assigned static (some say "persistent") addresses, as the areas are
small enough and the requests are few enough to warrant sharing between
these towns for ease of administration and also more efficient address use.
Normally we just put a mac address reservation for the client into the DHCP
server and it works. However, since the relay-agent IP addresses are on
different networks, and each system already has subnet declarations, how do
we share a pool between them?  Is there a key phrase in the config that
forces the server to hand out an address based on MAC address, bypassing the
checks-and-balances that the shared-subnet statements give?

It seems to make sense to me that if a MAC reservation has been made, it
should take precedence (based on the "most specific" rules that apply to
other IP addressing things) over anything else that the server knows about.

Does anyone have any ideas on how I can make this work?  I can put actual
examples of subnets and VLAN info up here, but it is way complex, possibly
more complex than is needed to solve the problem.


Alex Moen

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