On 10/13/2011 11:43 AM, John Foust wrote:
At 10:05 AM 10/13/2011, Dennis Boone wrote:
grievous misunderstanding of the common "one
external IP address"
service. The device will hand you more than one internal IP. If it's
equipped with one port and not doing NAT, then it is expecting you to
supply a firewall device, not to plug directly into it. The firewall
device will then do NAT and hand you multiple internal addresses.
Yeah, well, the modem will still only bind to one MAC address until you
power-cycle them, and they'll still only hand out one address via
DHCP, and it'll be a 192.168.1.xxx. Go figure. This is true for
the ATT DSL and Charter Cable modems I see in my area.
Arguably it simplifies the situation for the one modem, one computer
user. It doesn't let you simply add a switch to connect multiple
devices. It lets the ISP upsell the consumer to a four-port
combo firewall/router/wireless/modem.
Verizon(both DSL and FIOS) and Comcast(cable modem) who are the
predominant carriers in my area give out wireless *routers* standard and
have done so for at least 5 or 6 years.
There are no more DSL *modems* or cable *modems* that operate like you
suggest. If I go back about 10 years, yes, Adelphia(before bought by
Comcast) would pass out cable modems. My parents got DSL about 8 years
+ ago, and the initial device was in fact a router.
So the routers, performing the NAT, pass out multiple internal
192.168.x.x/24 (RFC 1918 addresses) and then translate to the single
external IP address assigned via DHCP if it's cable service, and PPPoEoA
if it's ADSL.
You can't natively attach directly to the cable port (because it's
coax), or the ADSL port (because, well, it's ADSL) and so the modem
functionality is directly built into the routers.
In FIOS installations that give you native RJ-45 ethernet ports (what I
have, much better than the damn moca connections), the behavior is as
you describe. If you connect directly to the ONT (optical network
terminal), a single external IP address assigned and locked to your MAC
via DHCP. However, every FIOS installation comes with a free router
(and required for use with moca, unless you have a moca->ethernet
bridge) and always have. I had FIOS access within three weeks of them
pulling the single-mode fiber down my street.
The days of the ISPs trying to upsell a router(or wireless router) are
long gone. Consumers now-a-days demand wireless routers standard.
Keith