I just purchased a SB5120 and registered it with my ISP.
Seems to work fine so far, but I'd like to configure it
just a little.

After browsing through the web interface (which is not
even protected by a password), I found that all you can do
is: 1) reset the modem to defaults, and 2) reboot it.

So I'm jumping through hoops with Motorola tech support.
After telling them that there's nothing in the web interface
that will allow me to change things (like LAN IP, shut off the
DHCP server, set a password, etc), their answer was this:

"There are no changes that can be made in the configuration
menus of the SBG5120 Cable Modem other then resetting the modem."

Uh... yeah, no kidding. I think that was my question in the
first place.

Does anybody have info on configuring the SB5120, or do I
need to return it for a refund ?

Thanks

Hose A. Cuervo wrote:

Let's alter that quote just a little to make it clearer:

"There are no changes that can be made BY END USERS in the configuration
menus of the SBG5120 Cable Modem other then resetting the modem."

Changes to the modem configuration are made by the owners of the network
that it is placed on: That is, the cable company. A configuration file is
downloaded to the cable modem whenever it connects after being reset. You,
the end user, do not get to configure any component on the cable company's
network, including the cable modem that you may have bought to place on that
network.

--
Warren H.

==========
Disclaimer: My views reflect those of myself, and not my
employer, my friends, nor (as she often tells me) my wife.
Any resemblance to the views of anybody living or dead is
coincidental. No animals were hurt in the writing of this
response -- unless you count my dog who desperately wants
to go outside now.

Compare and buy TaxCut and TurboTax Software:
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Hose A. Cuervo wrote:
The ISP controls the modem. Add a router between the modem and
the PC and do your config there. Netgear/Linksys routers are
cheap (at least here in the US - $30-40 on sale after rebate)
and they give you added security to protect your PC. Get a
wireless G router if you need wireless - else just get a wired
one for maybe $10 less. Either should have a 4-port switch to
connect your wired computers.

Bill M. wrote:
If those are the only alternatives the OP will accept, then the OP needs
to abandon broadband internet. See Warren's post in this thread.

Q

$Bill wrote:
Right. When the modem is reset, my ISP uploads a config to the
tftp server running on the cable modem. I agree that my ISP has
the right to control equipment connected to it's network, including
blocking certain netbios garbage.

But does my ISP have the right to configure things on my LAN ?
What if someone in the same office here decides to connect to
the web interface on 192.168.100.1 and keep resetting the damn
thing ? Don't I have the right to configure a password on MY side
of the network ? And don't I have the right to change the LAN IP
from the default of 192.168.100.1 to suit the IP numbering on my
LAN as I see fit? This would have nothing at all to do with my ISP,
and they shouldn't even care. If I can monitor the cable modem
to graph the traffic statitistics using SNMP, shouldn't I be able to
set the read community string to something other than the default
of "public" ?

Hose A. Cuervo wrote:
No. And they don't.

In the same office? This isn't a residential account?

If they work in the same office as you, and are on the same LAN that you're
on, then talk to your network admin or your boss about what they're doing.

If I misunderstand what you mean by "the same office", and you meant someone
else on the same node as you on the cable company's HFC network, then it's
not going to happen that way. Someone else looking for 192.168.100.1 won't
see your modem's interface. They'll see their modem's interface.


You can do whatever you want on your side of the network, but I haven't seen
any cablemodems that allow you to change the IP address of their web
interface. But if you place a router between your LAN and the cablenetwork,
that's a moot point.

No. The cablemodem is not on your network. It is on the cable company's
network. If you haven't placed a router between it and your computers, then
you've placed all your computers on their network. A router would delineate
where your network ends, and their network begins. Everything on one side of
the router would be on your network. Everything on the other side of it
would be on the cable company's network. You only get to do things on the
cable company's network that they decide to allow you to do, and controlling
the modem's configuration isn't one of them.

You get to stay on your side, and do whatever you want to your LAN. They get
to stay on their side and do whatever they want to their WAN. The modem is
part of their WAN.

--
Warren H.

==========
Disclaimer: My views reflect those of myself, and not my
employer, my friends, nor (as she often tells me) my wife.
Any resemblance to the views of anybody living or dead is
coincidental. No animals were hurt in the writing of this
response -- unless you count my dog who desperately wants
to go outside now.

Compare and buy TaxCut and TurboTax Software:
http://www.holzemville.com/taxes/

Warren wrote:
I used to have a D-Link that would.

According to Motorola's own pdf datasheet, the SB5120
"Supports up to 32 users (one via USB and 31 via Ethernet
or 32 users on Ethernet)"

Also, the web interface shows a screen under the "Configuration" link with
the following info:

" DHCP Server Enabled
The SURFboard cable modem can be used as a gateway to the Internet by a
maximum of 32 users on a Local Area Network (LAN). When the Cable Modem
is disconnected from the Internet, users on the LAN can be dynamically
assigned IP Addresses by the Cable Modem DHCP Server. These addresses
are assigned from an address pool which begins with 192.168.100.11 and
ends with 192.168.100.42. Statically assigned IP addresses for other
devices on the LAN should be chosen from outside of this range"

Well, 42 minus 11 equals the 31 IP addresses they're talking about
in the pdf datasheet. "can be used as a gateway to the Internet"
"gateway" is a router, specifically a NAT router. So what
I'm trying to do is whatever I want on the LAN side. I get to stay on
my side, and they get to do whatever they want to their WAN.

By the "same office", I was actually simplifying and stretching the truth
a little bit. It _is_ a residential account, but will soon be part of a
VPN.
My whole point is that I paid for this sucker, and I do not have
administrative
control over the part of it that is connected to my side of the network.
Whether I actually set a password on the web interface, or change the
SNMP read or write strings is beside the point. I _should_ have these
abilities whether I decide to use them or not.

"Hose A. Cuervo" <jose@abc.xyz.com.net.org.us.ru> wrote in message
news:11sujs1flq5doc9@corp.supernews.com...
Most cable modems support more than one user, but that requires more than
one IP address from your cable provider. Cable modems are usually
provisioned for only 1 IP address. The provider will probably charge
additional fees to give you more IP addresses. Most people put a router
(they're pretty cheap) between their LAN and the cable modem, giving them
complete control without paying for extra IP addresses from the provider.

Hose A. Cuervo wrote:
That you paid for the modem is irrelevant. You put it on their network. They
get to configure things on their network.

You want to configure your cablemodem? Take it off the cable company's
network. Do whatever you want to it. But once you put it back on their
network, you are agreeing that they will be allowed to reconfigure it for
their network.

You get to configure things on your network. But your network is on the
opposite side of the router from where the cablemodem is. The cablemodem is
not on your network. It's on their network.

--
Warren H.

==========
Disclaimer: My views reflect those of myself, and not my
employer, my friends, nor (as she often tells me) my wife.
Any resemblance to the views of anybody living or dead is
coincidental. No animals were hurt in the writing of this
response -- unless you count my dog who desperately wants
to go outside now.

Compare and buy TaxCut and TurboTax Software:
http://www.holzemville.com/taxes/

Mike Rush wrote:
This post was helpful, thanks. It explains why when I connect up two
workstations through a switch or hub to the cable modem, I receive two
dhcp assigned publicly routable IPs from my ISP. The grade of
service I'm paying for allows me a max of 3.

But I am still confused about the statement I posted previously which
shows up in the cable modem's web interface, stating that up to 32
dhcp addresses can be assigned, within the IP block of 192.168.100.*

I have verified that this is true. When I disconnect the cable, or kick the
modem into standby, I can fire up 3 or 4 boxes and each one gets a dhcp
assigned address in the 192.168.100.* range. But what use are these
IPs, if they cannot be routed out and NAT translated once the cable is
reconnected to the WAN ?

Lets say I hook up a router with between my LAN and the modem.
The dhcp server on the cable modem seems pointless if the only way to
get it working on the lan is to disconnect the WAN side temporarily. I
could
configure the router to NAT the assigned addresses out, and then connect
up the cable again. What a mess. Better to run a dhcp server on
the router and use it to NAT everything out.

I'm sure that somewhere buried in encrypted archives somewhere at
Motorola, there is complete documentation on how to tweak every
feature of the SB5120. But lets face it, they don't want the average
end user messing with it. Unfortunate for those of us who wish to
learn and experiment. Not everybody wants to hack, do damage,
or violate the terms of acceptable use just for the thrill of it.

Thanks to everybody for your input, and best wishes
I'm out of here for awhile......

Hose A. Cuervo wrote:
Their use is two-fold: One is that when the HFC network is down, the devices
on the user side of the cablemodem still have connectivity with each other.
The second reason is that it was no big deal to make this capability
available for up to 32 devices than it was to make it available to a more
reasonable three or four devices, but 32 looks so much better to the
marketing department.

The cablemodem, when connected to the HFC network, is supposed to act as a
bridge. When it's disconnected from the HFC network, it's nothing but a DHCP
server, which is something it's not when it's connected to the HFC network
unless the admins of the HFC network want to run their network that way.
(Most don't.) The cablemodem is not a router. It's not even a switch or hub.
That's not how it was designed to work.

Well, let's put it this way: If you're using the cablemodem without
connecting it to an HFC network, there's nothing to configure. If you're
using the cablemodem connected to an HFC network, it's no more your business
to configure it than it is for you to be configuring the CMTS. It has
nothing to do with whether you are average, advanced, or totally unclear on
the concept of how things work.

Your desire to learn does not trump the cable company's need to protect
their network. If you did manager to figure out how to hack into the modem,
there are absolutely no changes that you can make that wouldn't be a
violation of your terms of service. The fact that you think it's virtuous to
hack into a network that you have no business hacking into indicates that
you just don't understand. I'd like to learn what my neighbors are doing
behind their closed blinds. Is it okay that I want to peep in their window?
It's not that I want to do any damage. I just want to learn. Is that wrong?
You bet it is! Academic intent does not trump privacy or property rights.
Hacking in to learn is just as wrong as hacking in to do damage. Your intent
is irrelevant. Only your actions matter, and your actions most definitely
would be a violation of the terms of service.

Your curiosity would be better aimed at learning how HFC networks operate
than learning how you can misconfigure a cablemodem.

--
Warren H.

==========
Disclaimer: My views reflect those of myself, and not my
employer, my friends, nor (as she often tells me) my wife.
Any resemblance to the views of anybody living or dead is
coincidental. No animals were hurt in the writing of this
response -- unless you count my dog who desperately wants
to go outside now.

Compare and buy TaxCut and TurboTax Software:
http://www.holzemville.com/taxes/

"Warren" wrote:

Well said. I wish the Bush administration would concur.

*TimDaniels*