I have Cable Modem service from Time Warner Road Runner in NYC.
The way they work it you get up to 5 IP addresses for each cable
modem you have. The problem I have run into is that the modem gets
assigned the number of addresses you pay for up front.
The modem then assigns them, one to each MAC address it sees until the
number of addresses is used up. Now if you connect a switch to the
cable modem the LAN and WAN MAC addresses of the switch will be seen
by the modem and two of your IP addresses will become inaccessible.
As far as I can tell there is no way to specify to the modem which
MAC addresses should be issued IP addresses.
This means that for the first three addresses you get one computer.
Four addresses for two computers, five addresses for three computers.
Now if you use a NAT device the WAN MAC address is seen first and gets
an IP address and then everything else gets private addressing.
Even if you want to play by the book, DOCSIS modems make things very
difficult.
- Jeff
Any ideas?
I wish it were per-residence pricing. Here, if you want a 2nd (3rd, 4th,
...) IP address, the cable ISP expects you to connect a 2nd (3rd, 4th,
...) cable modem to the cable line. And they then charge additional fees
for each such additional connection.
Tony Hansen
tony(_at_)att(_dot_)com
Keith Moore wrote:
IP Addresses cannot at once be scarce enough to charge for and
non-scarce enough that scarcity is a non-issue.
IPv4 scarcity is an issue, at least for customers. Whether it's
an issue for large ISPs is a different question.
The cable ISP isn't really charging per-IP addresses; rather it's
charging per-residence. The motiviation is not the scarcity of IP
addresses, but the scarcity of available dollars per customer -
in other words, they have an assumption that the amount of income they
can get from residental Internet service is more-or-less a constant
times the number of residental customers served.
So they use flat-rate, per-residence pricing to attract the largest
number of residential customers. But they get annoyed when the
service is shared over multiple residences. They'd get just as
annoyed if the mechanism were IPv6 instead of NAT.
Keith
Jeffrey Altman * Sr.Software Designer C-Kermit 8.0 Beta available
The Kermit Project @ Columbia University includes Secure Telnet and FTP
http://www.kermit-project.org/ using Kerberos, SRP, and
kermit-support(_at_)kermit-project(_dot_)org OpenSSL. SSH soon to
follow.