Quote:
and in the process I made the interesting discovery that Virgin appear to assign IP based on the MAC address of whatever is connected to the cable modem I set the MAC to be the same as the old router, to keep the tests consistent.


When I had a cable modem way back in 2001 the MAC address was used as a authentication feature. The cable modem was effectively paired with the network card. Changing the network card or putting a router in instead resulted in a call to ntl to change the MAC address they had on file...... actually when I added the router I just gave it the MAC address of the network card it replaced, so it just worked.
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Cheers,

Andy M