Multiple ethernets on one cable modem

[mcmanus at AppliedTheory.com (Patrick McManus)]

okay.. my answers where are for the LanCity modems.. according to some
chatter on the newsgroups they're going to a different kind (a DOCSIS
compat model) in some places.. but the network is dominated by lancity
right now.

:: If this is the case, and according to the information we've tossed around so
:: far, new devices with invalid MACs will not have their packets forwarded by
:: the modem?

no, new devices with unregistered MACs will not have their DHCP
requests responded to by the DHCP server.

[out of order quote]
:: I've always thought the modems were somewhat analogous to "smart hubs". Does
:: anyone know of any technical descriptions of M1X's setup? Or the modems

that is exactly how the lancity modems work. (smart hubs are
traditionally called bridges).. but what you're missing is how they
decide what to filter to.. They filter for the first MAC address they
see on the home side.. (if you've got the multiple (N) computer option
then they filter for the first N addresses they see on the home
side).. that MAC is not hardcoded.. it's hardcoded in the DHCP server,
not the modem.

this is why when you change your NIC you have to power cycle the modem
(to reset the address it will filter).. it really is important to do
here, while 99% of the other times m1x has you do it it is pointless.

:: Perhaps they have a rule on the DHCP server : "The cable modem with a MAC
:: address of X is allowed to request up to Y IP addresses". ?

while the modem's do have L3 addresses (for snmp and assorted things), in
general you can just ignore this.. the DHCP transaction betweeen
computer and server just passes through the modem.. it doesn't appear
to play a role in it at all.

-P
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