dhcp3 failover protocol failure

[Rene Hogendoorn <rene.hogendoorn@hccnet.nl>]

I am running two debian woody dhcp3 servers (version 3.0+3.0.1rc9-2.2)
that are configured to use a common address pool with fail-over.
Whenever one of the servers fails, the other server takes over
correctly.
After a certain time running as stand-alone, the server stops issuing
addresses with an error message "peer holds all free leases".
The pool is about 6 times larger than the total number of machines.

I have no idea what is causing this. I hope someone more knowledgeable
can point me into the right direction.

Regards
Rene Hogendoorn


dhcpd.conf:
------------------------------------------------------------------
use-host-decl-names on;

default-lease-time 259200;
max-lease-time 432000;
ddns-update-style interim;
ddns-domainname "montessori-zwolle.nl";
ddns-updates on;

include "/etc/dhcp3/dhcp.key";

zone montessori-zwolle.nl. {
   primary 127.0.0.1;
   key dhcp-maan;
}

zone 0.168.192.in-addr.arpa. {
   primary 127.0.0.1;
   key dhcp-maan;
}
 
failover peer "melkweg.montessori-zwolle.nl" {
   primary;                        # we are a primary
   address 192.168.0.3;            # address to listen on
   peer address 192.168.0.6;       # who we connect to
   port 519;                       # port to use for msgs
   peer port 521;                  # where we send msgs
   max-response-delay 60;          # how many seconds to
                                   # wait before we
                                   # determine a
                                   # failure 
   max-unacked-updates 10;         # number of unacked 
                                   # packets to send
   mclt 3600;                      # only defined on primary
   split 128;
   load balance max seconds 3;
}       

option option-128 code 128 = string;
option option-160 code 160 = string;
option option-184 code 184 = string;
option option-193 code 193 = string;
option option-194 code 194 = string;

subnet 192.168.0.0 netmask 255.255.255.0 {
   pool {
      failover peer "melkweg.montessori-zwolle.nl";
      deny dynamic bootp clients;
      range 192.168.0.64 192.168.0.192;
   }

   option broadcast-address 192.168.0.255;
   option routers 192.168.0.1;

   option domain-name "montessori-zwolle.nl";
   option domain-name-servers ns1.montessori-zwolle.nl,
ns2.montessori-zwolle.nl;

   option netbios-name-servers universe;
   option netbios-dd-server universe;
   option netbios-node-type 8;

   option option-128 e4:45:74:68:00:00;
   option option-160 "timeout=10:default=193";
   option option-184 "Installatie menu";
   option option-193 "Via server:::-::0i:";
   option option-194 "Locaal:::/dev/hda1::0i:ip=off";

   #filename "/host/nbi/vmlinuz-2.4.1-ac3-nbi.tagged";
   #option root-path "/host/nfsroot";
}

# Fixed IP addresses can also be specified for hosts.   These addresses
# should not also be listed as being available for dynamic assignment.
# Hosts for which fixed IP addresses have been specified can boot using
# BOOTP or DHCP.   Hosts for which no fixed address is specified can
only
# be booted with DHCP, unless there is an address range on the subnet
# to which a BOOTP client is connected which has the dynamic-bootp flag
# set.

host aarde {
   hardware ethernet 00:02:44:4f:b4:70;
   fixed-address aarde;
}