mounting root from NFS via ROOTDEVNAME

Hi,

I'm trying to netboot a system where the root device is specified in the kernel via ROOTDEVNAME:

options         BOOTP
options         BOOTP_NFSROOT
options         BOOTP_NFSV3
options         BOOTP_COMPAT
options         BOOTP_WIRED_TO=em4
options         ROOTDEVNAME=\"nfs:10.11.12.13:/usr/home/elars/dst\"

I was under the assumption that specifying a ROOTDEVNAME in the kernel config would override the "root-path" option in DHCP, or at least take effect when "root-path" wasn't provided via DHCP, but that doesn't seem to be the case. The system configures it's address correctly over em4, but then enters a loop:

em4: link state changed to UP
Received DHCP Offer packet on em4 from 0.0.0.0 (accepted) (no root path)
Sending DHCP Request packet from interface em4 (XX:XX:XX:XX:XX:XX)
Received DHCP Ack packet on em4 from 0.0.0.0 (accepted) (no root path)
Received DHCP Ack packet on em4 from 0.0.0.0 (accepted) (no root path)
DHCP/BOOTP timeout for server 255.255.255.255
Received DHCP Ack packet on em4 from 0.0.0.0 (accepted) (no root path)
DHCP/BOOTP timeout for server 255.255.255.255
...

If I hand out a root path via DHCP the system boots fine, but the idea here is to be able to boot different root devices without needing to diddle dhcpd.conf. Can this be done?

Thanks,
Lars