DHCP failover

I am having a problem configuring the failover on my DHCP server.
When not configured for failover clients are able to receive IPs. Once I change the configuration, the dhcp starts up without any errors, but if I try to get an IP by ipconfig /renew, I get the DHCP in unreachable message.
I have even stripped down the config file to one subnet and connected the a pc to it directly with a crossover cable. I can ping it and telnet to it, but I can’t get an IP.
One question that I have is: isthe secondary DHCP server required for it to work?
I dont have the secondary hooked up, but the whole point of failover is for it to be able to take over the failed one.

Please help,

Thanx