dhcpd would offer leases for 1800 seconds only to nodes with static ip addresses defined in /lib/ndb/local, ignoring the -M argument (minlease). 

before:

plan9 Oct  3 13:05:17 Request(10.128.101.134->10.128.101.3) xid(3dce6644)flag(0)ea(00304827089a)ci(10.128.101.134)id(id0100304827089a)leas(1800)need(mask router dns host dom ntpserver )
plan9 Oct  3 13:05:17 Ack(10.128.101.3-10.128.101.134)id(id0100304827089a)ci(10.128.101.134)gi(0.0.0.0)yi(10.128.101.134)si(10.128.101.3) typ(5)leas(256000)sid(10.128.101.3)mask(/112)router(10.128.10.241)host(ahti007.ccstar.lanl.gov)dns(10.128.10.241 10.128.101.3)dom(ccstar.lanl.gov)128(10.128.101.3)129(10.128.101.3)vendorinfo(0 4 10 128 101 3 129 4 10 128 101 3


after (see the leas() section):

plan9 Oct  3 13:10:18 Request(10.128.101.128->10.128.101.3) xid(13672ae9)flag(0)ea(003048270734)ci(10.128.101.128)id(id01003048270734)leas(1800)need(mask router dns host dom ntpserver )
plan9 Oct  3 13:10:18 Ack(10.128.101.3-10.128.101.128)id(id01003048270734)ci(10.128.101.128)gi(0.0.0.0)yi(10.128.101.128)si(10.128.101.3) typ(5)leas(256000)sid(10.128.101.3)mask(/112)router(10.128.10.241)host(ahti001.ccstar.lanl.gov)dns(10.128.10.241 10.128.101.3)dom(ccstar.lanl.gov)128(10.128.101.3)129(10.128.101.3)vendorinfo(0 4 10 128 101 3 129 4 10 128 101 3

we have a large cluster which uses dhcp, it generates 4 megs worth of ipboot logs a day with all machines requesting addresses all the time.