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Old 02-10-2008, 03:29 AM
 
Default Interrogate network for devices

Sorry for the OT, but unable to raise anyone at comcast right now.

I think I recall having read somewhere that one can do something to
discover what devices are on a network (Home lan). And what there
addresses are.

I've recently switched from DSL to Cable connection but still have
both working currently.

I had assumed my netgear-firewall/router would find the Cable modem and
be able to talk to it, but that isn't happening.

I can connect the cable modem direct to a pc and using the software
that comes with it establish a connection to the internet, but I
wanted to have that firewall/router in between the cable modem and home
pcs.

But that is only on a windows machine.

The help file that comes with the modem provides no information about
how one talks to the modem. No ethernet address is supplied. However
it is an ethernet device and connects to the pc with ethernet cable.

Apparently comcast felt it wiser to provide no details and let its
software do the connecting.

But can't I learn the IP address (inward facing) of the modem? The IP
from outside is of course visible to ipconfig, when connecting to
internet from a windows machine thru the cable modem, but I see
nothing that indicates what its lanside ethernet address is.

Its obviously connecting to the pc with dhcp so setting the netgear to
listen for dhcp seemed like it should work... but doesn't.

I thought I would be able to connect to the cable modem with a browser
and maybe learn enough to make the netgear router/firewall connect to
it, or one of my gentoo boxes, so have tried a few of the
semi-standard addresses other ethernet hubs/routers etc default to, like
192.168.0.1, 192.168.1.1 and a few more.

--
gentoo-user@lists.gentoo.org mailing list
 
Old 02-10-2008, 03:44 AM
Hal Martin
 
Default Interrogate network for devices

Perhaps you need a cross over cable between the modem and the router?

-Hal


reader@newsguy.com wrote:
> Sorry for the OT, but unable to raise anyone at comcast right now.
>
> I think I recall having read somewhere that one can do something to
> discover what devices are on a network (Home lan). And what there
> addresses are.
>
> I've recently switched from DSL to Cable connection but still have
> both working currently.
>
> I had assumed my netgear-firewall/router would find the Cable modem and
> be able to talk to it, but that isn't happening.
>
> I can connect the cable modem direct to a pc and using the software
> that comes with it establish a connection to the internet, but I
> wanted to have that firewall/router in between the cable modem and home
> pcs.
>
> But that is only on a windows machine.
>
> The help file that comes with the modem provides no information about
> how one talks to the modem. No ethernet address is supplied. However
> it is an ethernet device and connects to the pc with ethernet cable.
>
> Apparently comcast felt it wiser to provide no details and let its
> software do the connecting.
>
> But can't I learn the IP address (inward facing) of the modem? The IP
> from outside is of course visible to ipconfig, when connecting to
> internet from a windows machine thru the cable modem, but I see
> nothing that indicates what its lanside ethernet address is.
>
> Its obviously connecting to the pc with dhcp so setting the netgear to
> listen for dhcp seemed like it should work... but doesn't.
>
> I thought I would be able to connect to the cable modem with a browser
> and maybe learn enough to make the netgear router/firewall connect to
> it, or one of my gentoo boxes, so have tried a few of the
> semi-standard addresses other ethernet hubs/routers etc default to, like
> 192.168.0.1, 192.168.1.1 and a few more.
>
>

--
gentoo-user@lists.gentoo.org mailing list
 
Old 02-10-2008, 04:46 AM
Dan Farrell
 
Default Interrogate network for devices

On Sat, 09 Feb 2008 22:29:15 -0600
reader@newsguy.com wrote:

> Sorry for the OT, but unable to raise anyone at comcast right now.
Really? I didn't think that was possible... although sometimes it's
good to call twice, get another opinion.

> I think I recall having read somewhere that one can do something to
> discover what devices are on a network (Home lan). And what there
> addresses are.

the network devices of those boxes have fc1918 private addresses i'm
sure. even if your router would forward packets from the outside in
(which can usually be configured), comcast isn't going to route them
to your router.

your external address is, of course, somewhat available, and the
device listening to that address (your router) is therefore
potentially vulnerable. Run a good firewall and you'll have knowledge
of what happens to incoming connections (generally, it would be best to
ignore them). linux makes a very good firewall.
> I've recently switched from DSL to Cable connection but still have
> both working currently.
smart!
> I had assumed my netgear-firewall/router would find the Cable modem
> and be able to talk to it, but that isn't happening.
i've never heard of that happening. ...
> I can connect the cable modem direct to a pc and using the software
> that comes with it establish a connection to the internet, but I
> wanted to have that firewall/router in between the cable modem and
> home pcs.
In my experience (w/ comcast), you connect the modem to a network port
via ethernet and then request a dhcp address. I never used comcast's
software in windows or linux.

> But that is only on a windows machine.

> The help file that comes with the modem provides no information about
> how one talks to the modem. No ethernet address is supplied. However
> it is an ethernet device and connects to the pc with ethernet cable.
>
> Apparently comcast felt it wiser to provide no details and let its
> software do the connecting.

It's more transparent. The network device on the modem holds your
public ip address. The modem has nothing to say.

Some modems, no doubt, have built-in gateway/router/firewalls, but not
all.

> But can't I learn the IP address (inward facing) of the modem? The IP
> from outside is of course visible to ipconfig, when connecting to
> internet from a windows machine thru the cable modem, but I see
> nothing that indicates what its lanside ethernet address is.

It doesn't have one. (If it did, you'd need to use it to reach the
outside.) Instead your outside ip is 'on' the computer itself.

> Its obviously connecting to the pc with dhcp so setting the netgear to
> listen for dhcp seemed like it should work... but doesn't.

the modem doesn't do the dhcp though, the computer asks and a dhcp
server in comcast-land gives out a lease.

i would think your router supports it - but you'd be using dhcp to
request a lease from netgear's point of view, not listening.
'listening' for dhcp sounds more like serving addresses on the local
network than using dhcp for external configuration.

> I thought I would be able to connect to the cable modem with a browser
> and maybe learn enough to make the netgear router/firewall connect to
> it, or one of my gentoo boxes, so have tried a few of the
> semi-standard addresses other ethernet hubs/routers etc default to,
> like 192.168.0.1, 192.168.1.1 and a few more.

as i said, it probably won't have such an address. it is transparent
to everyone but comcast itself, which evidently delivers some sort of
point-to-point-like service .

but the good news is gentoo _should_ be
able to use it just fine. i didn't have any problems. the netgear
should do fine as well, i'm surprised you're having problems at all.

well, i hope that helps. feel free to contact me if you have any more
questions.
--
gentoo-user@lists.gentoo.org mailing list
 
Old 02-10-2008, 11:55 AM
Mick
 
Default Interrogate network for devices

On Sunday 10 February 2008, reader@newsguy.com wrote:
> Sorry for the OT, but unable to raise anyone at comcast right now.
>
> I think I recall having read somewhere that one can do something to
> discover what devices are on a network (Home lan). And what there
> addresses are.

You are looking for route and arp commands. However, if you are not part of a
network all you might see is your PC's loopback entry - the arp and routing
tables will be empty.

> I've recently switched from DSL to Cable connection but still have
> both working currently.
>
> I had assumed my netgear-firewall/router would find the Cable modem and
> be able to talk to it, but that isn't happening.

This could be for a number of reasons. Is the cable modem a pure modem, or is
it also a router? Is authentication to the ISP's network configured at the
PC, or is it configured at the modem?

If the authentication is configured at the PC/client end rather than the
modem, then you are probably not using the correct encapsulation for the
cable network and, or have not cloned/spoofed the MAC address of the
nominated client (your PC). I guess that your ADSL will be using PPP over
ATM (PPPoA), if it's anything like what we have in most of the UK, while your
cable is most likely using PPP over Ethernet (PPPoE). In any case, you will
need to change the respective settings in your Netgear router. BTW, which
router is it? If it is one of the DG834 domestic models, these have both
(ADSL) modem and router combined into one unit. Again, depending on whether
your cable modem acts as a bridge or as a client on the Comcast network you
may or may not need to set up authentication on the router side (in the
Netgear modem configuration).

> I can connect the cable modem direct to a pc and using the software
> that comes with it establish a connection to the internet, but I
> wanted to have that firewall/router in between the cable modem and home
> pcs.
>
> But that is only on a windows machine.

That should not stop you finding out what IP address the PC uses to connect to
the modem and if needed what the MAC address of the PC's NIC is that Comcast
has registered as a legitimate client. Go to My Connections and select the
NIC being used to connect to the modem and then click on Status/Support and
note what the IP Address: shows. If this a private reserved LAN IP address
then check what the Default Gateway: IP address is. Use that in a browser,
or telnet console to connect to your modem. If however this is an Internet
address then this won't be good for connecting to modem, which is now acting
as a bridge to the ISP's network - the IP address is served by your ISP's
dhcp server. Another way to find out what IP addresses are being seen by the
PC is to go to Run and enter ipconfig /all. Note the IP Address: and Default
Gateway: as above. Also note the MAC address (this is called Physical
Address). In summary, enter the MAC address into your Netgear router and try
to connect without authentication, in the hope that the cable modem deals
with that. If this does not work, then also enter the username/passwd and
select PPPoE for encapsulation. In both cases select dhcp as opposed to
static IP on the router.

> The help file that comes with the modem provides no information about
> how one talks to the modem. No ethernet address is supplied. However
> it is an ethernet device and connects to the pc with ethernet cable.
>
> Apparently comcast felt it wiser to provide no details and let its
> software do the connecting.

This is because the vast majority of users out there will never want or be
able to connect to the modem. The few who connect could well mess it up and
raise fault tickets unnecessarily. So Comcast are trying to reduce user
generated errors proactively.

> But can't I learn the IP address (inward facing) of the modem? The IP
> from outside is of course visible to ipconfig, when connecting to
> internet from a windows machine thru the cable modem, but I see
> nothing that indicates what its lanside ethernet address is.
>
> Its obviously connecting to the pc with dhcp so setting the netgear to
> listen for dhcp seemed like it should work... but doesn't.

See above regarding the MAC cloning and authentication encapsulation.

> I thought I would be able to connect to the cable modem with a browser
> and maybe learn enough to make the netgear router/firewall connect to
> it, or one of my gentoo boxes, so have tried a few of the
> semi-standard addresses other ethernet hubs/routers etc default to, like
> 192.168.0.1, 192.168.1.1 and a few more.

Have you also tried:

192.168.1.254 and .255
10.10.10.1 and 10.1.10.1

BTW, before you try to connect to any of the above first change your Gentoo's
IP address statically, by running as root:

ifconfig 192.168.0.2

The exact number is not important as long as it is in the same subdomain (e.g.
192.168.0.0) and it does not conflict with the expected LAN IP address of the
router.

A quick way to see who's on the particular subdomain is to run nmap:
===========================================
$ nmap -sP 192.168.0.0/24

Starting Nmap 4.50 ( http://insecure.org ) at 2008-02-10 12:53 GMT
Host 192.168.0.1 appears to be up.
Host 192.168.0.6 appears to be up.
Nmap done: 256 IP addresses (2 hosts up) scanned in 14.301 seconds
===========================================

In this example I have scanned all addresses within the subdomain 192.168.0.0
after I set statically my PC's IP address to 192.168.0.6. As you can see
from the results above, by process of elimination 192.168.0.1 is the address
of the router.

HTH.
--
Regards,
Mick
 
Old 02-11-2008, 02:26 AM
Dan Farrell
 
Default Interrogate network for devices

On Sun, 10 Feb 2008 12:55:49 +0000
Mick <michaelkintzios@gmail.com> wrote:

> On Sunday 10 February 2008, reader@newsguy.com wrote:

> If the authentication is configured at the PC/client end rather than
> the modem, then you are probably not using the correct encapsulation
> for the cable network and, or have not cloned/spoofed the MAC address
> of the nominated client (your PC). I guess that your ADSL will be
> using PPP over ATM (PPPoA), if it's anything like what we have in
> most of the UK, while your cable is most likely using PPP over
> Ethernet (PPPoE).

> In any case, you will need to change the
> respective settings in your Netgear router. BTW, which router is
> it? If it is one of the DG834 domestic models, these have both
> (ADSL) modem and router combined into one unit. Again, depending on
> whether your cable modem acts as a bridge or as a client on the
> Comcast network you may or may not need to set up authentication on
> the router side (in the Netgear modem configuration).

Unless your comcast connection differs from my own, you won't need to
authenticate. Instead, they should have recorded your modem's MAC
address.

AFAIK we use ppp-oe for (a)dsl here in the states, and all cable modem
connections I've ever seen have been transparent (though no doubt they
use some sort of ppp as well)
--
gentoo-user@lists.gentoo.org mailing list
 
Old 02-11-2008, 02:52 AM
Dale
 
Default Interrogate network for devices

reader@newsguy.com wrote:

Sorry for the OT, but unable to raise anyone at comcast right now.

I think I recall having read somewhere that one can do something to
discover what devices are on a network (Home lan). And what there
addresses are.

I've recently switched from DSL to Cable connection but still have
both working currently.

I had assumed my netgear-firewall/router would find the Cable modem and
be able to talk to it, but that isn't happening.

I can connect the cable modem direct to a pc and using the software
that comes with it establish a connection to the internet, but I
wanted to have that firewall/router in between the cable modem and home
pcs.


But that is only on a windows machine.

The help file that comes with the modem provides no information about
how one talks to the modem. No ethernet address is supplied. However
it is an ethernet device and connects to the pc with ethernet cable.

Apparently comcast felt it wiser to provide no details and let its
software do the connecting.

But can't I learn the IP address (inward facing) of the modem? The IP
from outside is of course visible to ipconfig, when connecting to
internet from a windows machine thru the cable modem, but I see
nothing that indicates what its lanside ethernet address is.

Its obviously connecting to the pc with dhcp so setting the netgear to
listen for dhcp seemed like it should work... but doesn't.

I thought I would be able to connect to the cable modem with a browser
and maybe learn enough to make the netgear router/firewall connect to
it, or one of my gentoo boxes, so have tried a few of the
semi-standard addresses other ethernet hubs/routers etc default to, like
192.168.0.1, 192.168.1.1 and a few more.




I'm not sure if this will work for you or not but it worked for me when
I was at my ex's and we had cable there. Cut everything off. Turn on
the modem and wait a minute or two after the lights stop changing and
blinking. Turn on the next device, router in our case, and wait a few
minutes again. Then turn on the computers. I always cut on the one
hooked to the ethernet #1 port first but it may not matter. That was my
Linux box and it was always on, 24/7.


I also had to change the IP address on the router to a fixed address to
get it to work right. I think I had it set to 192.168.100.2. After
that, we had very little trouble with the connection. The modem itself
was 192.168.100.1. If you hook your computer directly to the modem, you
can see things like signal strength and stuff. Can't change anything
tho. You just get to look. I think it had like a reset button too.
Also, if I had anything between the computer and the modem, I could not
see the modem at all. YMMV.


Oh, we had Vista-Media to. If that matters any.

May not help but may be worth a shot in the dark.


Dale

:-) :-)
--

gentoo-user@lists.gentoo.org mailing list
 
Old 02-11-2008, 03:59 AM
Grant Edwards
 
Default Interrogate network for devices

On 2008-02-10, reader@newsguy.com <reader@newsguy.com> wrote:

> I can connect the cable modem direct to a pc and using the software
> that comes with it establish a connection to the internet, but I
> wanted to have that firewall/router in between the cable modem and home
> pcs.

You could install Wireshark and capture the traffic between the
modem and the PC in the case where it works. That would tell
you the modem's MAC address and whether the modem has an IP
address or not.

> The help file that comes with the modem provides no
> information about how one talks to the modem. No ethernet
> address is supplied. However it is an ethernet device and
> connects to the pc with ethernet cable.
>
> Apparently comcast felt it wiser to provide no details and let
> its software do the connecting.
>
> But can't I learn the IP address (inward facing) of the modem?

It may not have one.

> The IP from outside is of course visible to ipconfig, when
> connecting to internet from a windows machine thru the cable
> modem, but I see nothing that indicates what its lanside
> ethernet address is.

If the PC has an IP address that is visible from the outside,
then the modem is running as a bridge and might not have an IP
address at all.

> Its obviously connecting to the pc with dhcp so setting the
> netgear to listen for dhcp seemed like it should work... but
> doesn't.

I would think that if the netgear router is a DHCP client on
its WAN interface, then connecting the WAN interface to the
cable modem should work. I've done that with a few different
router/cable-modem combinations with Comcast (nee T-W), and it
always worked. Can you trace the newtork traffic between the
netgear and the cable modem? That would require either a hub
or a properly configured managed switch, so that may not be a
simple task.

> I thought I would be able to connect to the cable modem with a
> browser and maybe learn enough to make the netgear
> router/firewall connect to it, or one of my gentoo boxes, so
> have tried a few of the semi-standard addresses other ethernet
> hubs/routers etc default to, like 192.168.0.1, 192.168.1.1 and
> a few more.


--
Grant Edwards grante Yow! I'm also pre-POURED
at pre-MEDITATED and
visi.com pre-RAPHAELITE!!

--
gentoo-user@lists.gentoo.org mailing list
 
Old 02-11-2008, 05:19 AM
Dan Farrell
 
Default Interrogate network for devices

On Sun, 10 Feb 2008 21:52:14 -0600
Dale <dalek1967@bellsouth.net> wrote:

> I also had to change the IP address on the router to a fixed address
> to get it to work right. I think I had it set to 192.168.100.2.
> After that, we had very little trouble with the connection. The
> modem itself was 192.168.100.1. If you hook your computer directly
> to the modem, you can see things like signal strength and stuff.
> Can't change anything tho. You just get to look.

Interesting! I wonder if mine had a utility for something like that on
the disks that I didn't bother to open that came with the modem....

In this case it sounds a lot like a DMZ kind of thing, right? I see
DSL doing that a lot of the time. Often you can also turn it off and
use it as a dumb ppp or such. Other times, your stuck behind it and
may not even be able to forward ports.

Or maybe it's something different, something I haven't seen.
--
gentoo-user@lists.gentoo.org mailing list
 
Old 02-11-2008, 06:01 AM
Dale
 
Default Interrogate network for devices

Dan Farrell wrote:

On Sun, 10 Feb 2008 21:52:14 -0600
Dale <dalek1967@bellsouth.net> wrote:



I also had to change the IP address on the router to a fixed address
to get it to work right. I think I had it set to 192.168.100.2.
After that, we had very little trouble with the connection. The
modem itself was 192.168.100.1. If you hook your computer directly
to the modem, you can see things like signal strength and stuff.
Can't change anything tho. You just get to look.



Interesting! I wonder if mine had a utility for something like that on
the disks that I didn't bother to open that came with the modem....

In this case it sounds a lot like a DMZ kind of thing, right? I see
DSL doing that a lot of the time. Often you can also turn it off and
use it as a dumb ppp or such. Other times, your stuck behind it and
may not even be able to forward ports.

Or maybe it's something different, something I haven't seen.



I'm no guru on this thing but for some reason the DHCP part in the
Linksys router would just not accept the address from the modem. Sort
of weird in a way tho.


Since I use Linux only, I never installed any software. I just pointed
my browser to that address and up it popped. That would work when
looking for the modem or the router. Tho I could not get to the modem
if the router was in the middle. Not sure what the deal is on that.


If I had access to one I'd get you a screen shot or something but like I
said, that was my ex's thing. She is still mad that I left. She had
"issues" that I couldn't deal with. Ya know. ;-)


Dale

:-) :-) :-)

--
gentoo-user@lists.gentoo.org mailing list
 
Old 02-11-2008, 09:56 AM
 
Default Interrogate network for devices

reader@newsguy.com writes:

> I've recently switched from DSL to Cable connection but still have
> both working currently.

I've snipped all responses but carefully read through them. I think I
didn't provide enough info at the outset.

I see now that this cable modem has no ethernet address as several
posters have suggested.

Listing models may help the discussion so here they are:

The Comcast Cable modem: Scientific Atlanta-DPC2100RC (has MAC listed
on the sticker)

Two different Netgear Router/firewalls have been tried. Same router
but older and newer models:

Older Netgear:
FVS318 (Says Cable/DSL PROsafe VPN Firewall FVS318 across the front)

Newer Netgear:
FVS318v3 (Says Cable/DSL PROsafe VPN Firewall FVS318 across the front)

The newer one is a couple of years newer and purchased about 1 yr ago.

It may just be software differences but they do have somewhat
different interfaces. The older one is using the latest software it
is capable of loading, as is the newer one, but in the later case the
software is a newer version than the old one supports.

One curious thing here is that both of these Netgear routers have at
one time or another been connected to a Comcast provided modem and
worked fine. In both of those cases the Netgear using its connection
wizard, simply found and ID'ed the cable modem... and just worked from
there on. I only setup the lanside addressing since I prefer all
static addresses inside.

Ditto for DSL... again both Netgear routers have worked with DSL
routers and again the connection was established by simply running the
connection wizard.

In the current case, neither of these routers was able to just
identify and connect to the cable modem or internet through it. And
in both cases the wizard ends up saying the connection type is STATIC
and offers to accept the static addresses from user. I doubt the
addressing is really STATIC.

I think my next step here will be to take the IP address and
Nameserver from IPconfig (or netstat) on the windows box that will
connect using the Cable modem, and see if those addresses will work
when inserted into the netgears as static outside addresses to connect
to.

If that works, It may hold until a new address is issued for whatever
reason from comcast... and I may get some help from them by then.

I will report back if there is any interest?

--
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