How to not allocate any address to a specific host?

Douglas Armstrong doug at
Mon Mar 13 13:34:15 UTC 2006

One thing to remember is that the Win95 dhcp client is broken and will not
ask for a new address on boot unless the one it has is expired. 


Simon Hobson wrote: David Landgren wrote: class "obsolete-hosts" { match
pick-first-value (option dhcp-client-identifier, hardware); } # i000003492
subclass "obsolete-hosts" 00:0a:e4:36:7b:4b; shared-network example-net {
subnet netmask { range;
option ntp-servers; option time-servers; option
routers172.17.0.6; option domain-name ""; option
domain-name-servers,; option netbios-node-type 2;
option netbios-name-servers; default-lease-time 86400; # 1 days
max-lease-time 864000; # 10 days } subnet netmask {
pool { allow members of "obsolete-hosts"; deny unknown-clients;
default-lease-time 15; max-lease-time 10; range; } } } So,
what am I missing here? You don't have the right allow/deny statements.
Firstly, there is nothing to deny obsolete-hosts from the 172.17 subnet. So
in here you want "deny members of "obsolete-hosts"". Secondly, you have
mixedallow &deny in the 10.2 subnet. I believe this does NOT work as you
might expect. Having "allow members of "obsolete-hosts"" is sufficient to
deny anything NOT in that class. What is probably happening is that a client
with a 172.17 address is added to the obsolete-hosts class, but because it
isn't denied from having an address in that subnet, it can carry on leasing
that address. So you probably want something like : shared-network
example-net { subnet netmask { other stuff pool {
deny members of "obsolete-hosts"; range; } }
subnet10.2.0.0 netmask { default-lease-time 15;
max-lease-time 10; pool { allow members of "obsolete-hosts"; range; } } } Simon 

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