Create a dedicated configuration file /etc/dibbler/server.conf . Note, that the router requires to have a interface configured with an IPv6 address out of the defined subnet.

log-level 8 
log-mode short 
preference 0 
iface "eth1" {
 // also ranges can be defines, instead of exact values  t1 1800-2000  t2 2700-3000
  prefered-lifetime 3600
  valid-lifetime 7200
  class {
    pool 2001:6f8:12d8:1::/64
  }
  option dns-server fec0:0:0:1::1
  option domain domain.example
} 

Start server in foreground:

# dibbler-server run 
| Dibbler - a portable DHCPv6, version 0.7.3 (SERVER, Linux port) 
| Authors : Tomasz Mrugalski<thomson(at)klub.com.pl>,Marek Senderski<msend(at)o2.pl> 
| Licence : GNU GPL v2 only. Developed at Gdansk University of Technology. 
| Homepage: http://klub.com.pl/dhcpv6/ 
2009.05.28 10:18:48 Server Notice    My pid (1789) is stored in /var/lib/dibbler/server.pid 
2009.05.28 10:18:48 Server Notice    Detected iface eth0/3, MAC=54:52:00:01:23:45. 
2009.05.28 10:18:48 Server Notice    Detected iface eth1/2, MAC=54:52:00:67:89:ab. 
2009.05.28 10:18:48 Server Notice    Detected iface lo/1, MAC=00:00:00:00:00:00. 
2009.05.28 10:18:48 Server Debug     Skipping database loading. 
2009.05.28 10:18:48 Server Debug     Cache:server-cache.xml file: parsing started, expecting 0 entries. 
2009.05.28 10:18:48 Server Notice    Parsing /etc/dibbler/server.conf config file... 
18:48 Server Debug     Setting 0 generic option(s). 
18:48 Server Debug     0 per-client configurations (exceptions) added. 
18:48 Server Debug     Parsing /etc/dibbler/server.conf done. 
18:48 Server Info      0 client class(es) defined. 
18:48 Server Debug     1 interface(s) specified in /etc/dibbler/server.conf 
18:48 Server Info      Mapping allow, deny list to class 0:0 allow/deny entries in total. 
18:48 Server Info      Interface eth1/2 configuration has been loaded. 
18:48 Server Notice    Running in stateful mode. 
18:48 Server Info      My DUID is 00:01:00:01:11:aa:6d:a7:54:52:00:67:89:ab. 
18:48 Server Notice    Creating multicast (ff02::1:2) socket on eth1/2 (eth1/2) interface. 
18:48 Server Debug     Cache: size set to 1048576 bytes, 1 cache entry size is 87 bytes, so maximum 12052 address-client pair(s) may be cached. 
18:48 Server Notice    Accepting connections. Next event in 4294967295 second(s).