[Nottingham] Connecting router to Virgin/NTL cable

[Dave]

Hi folks,

I've previously been running ntlworld (now virgin) cable with a small 
£20 dlink (DI-604) NAT router behind a several-years-old ntl 
cablemodem.  I recall that when I installed it (the router) I had to add 
a rule opening port 68 to the outside or it wouldn't obtain an IP 
address from NTL.

I've now bought a newer dlink router (DIR-300) that also has wireless, 
but I can't seem to get it to obtain an IP address.  I've tried opening 
port 68 again, still no joy.  Unfortunately I've set and lost the admin 
password to the old router so I can't check exactly what I did that 
worked!  Any advice?  A lot of the group must have connected a router 
behind an ntl cablemodem at some point - is it normal to have to open 
port 68?  I clicked "clone MAC address" but this I think just clones the 
MAC address of the PC I used to configure it - is that necessary / correct?

Thanks in advance for any advice,
Cheers - Dave