Thread: Multiple IP on firewall?
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Old 13-01-2004, 11:56   #17
rdhw
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Location: Cambridge
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Re: Multiple IP on firewall?
Quote:
Originally Posted by SAC
The IP addressing on their cable network appears not to have been planned for any customers wanting to do anything more advanced.
I don't have certain knowledge of the Business offering, but I'm extrapolating from what I do know. Although you have been offered five IP addresses (allegedly fixed IP addresses, but I think you will find they change if NTL's local cable system is hugely reorganised), they are still (I think) allocated by DHCP: they are not true static IP addresses, just DHCP-allocated addresses which will stay the same each time the linked MAC address broadcasts for a DHCP configuration. So there has to be a unique one-to-one mapping between MAC addresses and IP addresses, in order that DHCP can tell which card is calling. DHCP servers can't cope with allocating more than one IP address to the same MAC address, so multiple appearances of the same MAC address in their database is normally an error condition.

So the sledgehammer solution is to fit 5 WAN interfaces to your SmoothWall, connect them to a switch and thence to the cable modem. Pretty ghastly, but should fix it.
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