Hi,
Some questions to clarify:
1.- ¿Is your DHCP server the same as your DNS and forwarding machine?
2.- The IP 192.168.100.179, ¿is this server or another? If another, ¿what should it do?
3.- ¿The host 'host.domain.org' is existing on your net? ¿What should it do?
4.- ¿Can you post /etc/dhcp3/dphcpd.conf so we can help improve this?
5.- ¿Is there some misconfigured firewall between the host amb the 192.168.100.179?
As you can see, we need some more info

emi