dhcp server setup: client doesn't accept DHCPOFFER

[Hiisi]

Dear all!
I'm trying to set up dhcp-server for my home network. This home server
has 3 nicks. It's connected to the Internet via eth0 and shares its
connection to the LAN hosts on eth1 and eth2 interfaces using
IP-forwarding (masquerade). Currently clients have to enter IP
manually. I would like it to be set automatically via dhcp. I
installed dhcp and modified dhcpd.conf as follows:
$ sudo cat /etc/dhcp/dhcpd.conf
# dhcpd.conf

ddns-update-style interim;
ignore client-updates;

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
authoritative;

log-facility local7;

subnet 192.168.2.0 netmask 255.255.255.0 {
  range 192.168.2.30 192.168.2.50;
  default-lease-time 86400;
  max-lease-time 86400;
  option routers 192.168.2.20;
  option broadcast-address 192.168.2.255;
  option subnet-mask 255.255.255.0;
  option domain-name-servers 192.168.0.1;
}

host ubuntu-virtual {
      hardware ethernet 08:00:27:84:b7:23;
      fixed-address 192.168.2.50;
}

Now I'm testing it on ubuntu virtual machine with no success. When
ubuntu tries to connect to the Internet I see this messages
in/var/log/messages on the server:
Oct  4 13:22:50 kello dhcpd: DHCPDISCOVER from 08:00:27:84:b7:23 via eth1
Oct  4 13:22:50 kello dhcpd: DHCPOFFER on 192.168.2.50 to
08:00:27:84:b7:23 via eth1
Oct  4 13:22:55 kello dhcpd: DHCPDISCOVER from 08:00:27:84:b7:23 via eth1
Oct  4 13:22:55 kello dhcpd: DHCPOFFER on 192.168.2.50 to
08:00:27:84:b7:23 via eth1

As in theory, I'm expecting it to send DHCPREQUEST in response to
server DHCPOFFER and server to hit back with DHCPACK. Why it doesn't
work? How can i debug it to find out what's wrong with it?
TIA
-- 
Hiisi.
Registered Linux User #487982. Be counted at: http://counter.li.org/
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