fc3 vpn linux client behind nat problem

hello i am running fc3 the vpn client connects to my cisco router, i am
unable to ping remote hosts. the only traffic on the ppp0 interface is
gre traffic. I am connected to the vpn behind a dlink router. i found a
patch here http://www.impsec.org/linux/masquerade/ip_masq_vpn.html
but i dont think this patch works for 2.6 kernel fc3. Does anyone know
if i can get this working without the patch? thanks.