Diskless boot fails when network card is reset before NFS root mount

[Daniel Feenberg]

http://www.freebsd.org/cgi/query-pr.cgi?pr=139363

suggests

   "the fix is to set boot.nfsroot.options="nfsv2" in
   /boot/loader.conf or via dhcp."

I can see how to set options in /boot/loader.conf, but I don't see how 
boot loader options can be set in dhcpd.conf. All I have is:

        next-server 66.251.72.4;
        filename "pxeboot";
        option root-path "66.251.72.44:/vol/vol1b/FreeBSD-7.2-root";

Where would the boot loader options go? Are they a numbered option? Which 
one?

Daniel Feenberg
NBER