linux.gentoo.user

--nextPart1705887.PJ6AoNuzDe
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

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 o=
f a=20
network all you might see is your PC's loopback entry - the arp and routing=
=20
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=20
it also a router? Is authentication to the ISP's network configured at the=
=20
PC, or is it configured at the modem?

If the authentication is configured at the PC/client end rather than the=20
modem, then you are probably not using the correct encapsulation for the=20
cable network and, or have not cloned/spoofed the MAC address of the=20
nominated client (your PC). I guess that your ADSL will be using PPP over=
=20
ATM (PPPoA), if it's anything like what we have in most of the UK, while yo=
ur=20
cable is most likely using PPP over Ethernet (PPPoE). In any case, you wil=
l=20
need to change the respective settings in your Netgear router. BTW, which=
=20
router is it? If it is one of the DG834 domestic models, these have both=20
(ADSL) modem and router combined into one unit. Again, depending on whethe=
r=20
your cable modem acts as a bridge or as a client on the Comcast network you=
=20
may or may not need to set up authentication on the router side (in the=20
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=20
the modem and if needed what the MAC address of the PC's NIC is that Comcas=
t=20
has registered as a legitimate client. Go to My Connections and select the=
=20
NIC being used to connect to the modem and then click on Status/Support and=
=20
note what the IP Address: shows. If this a private reserved LAN IP addres=
s=20
then check what the Default Gateway: IP address is. Use that in a browser,=
=20
or telnet console to connect to your modem. If however this is an Internet=
=20
address then this won't be good for connecting to modem, which is now actin=
g=20
as a bridge to the ISP's network - the IP address is served by your ISP's=20
dhcp server. Another way to find out what IP addresses are being seen by t=
he=20
PC is to go to Run and enter ipconfig /all. Note the IP Address: and Defau=
lt=20
Gateway: as above. Also note the MAC address (this is called Physical=20
Address). In summary, enter the MAC address into your Netgear router and t=
ry=20
to connect without authentication, in the hope that the cable modem deals=20
with that. If this does not work, then also enter the username/passwd and=
=20
select PPPoE for encapsulation. In both cases select dhcp as opposed to=20
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=
=20
able to connect to the modem. The few who connect could well mess it up an=
d=20
raise fault tickets unnecessarily. So Comcast are trying to reduce user=20
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:=20

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=20
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=
=2Eg.=20
192.168.0.0) and it does not conflict with the expected LAN IP address of t=
he=20
router.

A quick way to see who's on the particular subdomain is to run nmap:
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
$ 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
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

In this example I have scanned all addresses within the subdomain 192.168.0=
=2E0=20
after I set statically my PC's IP address to 192.168.0.6. As you can see=20
from the results above, by process of elimination 192.168.0.1 is the addres=
s=20
of the router.

HTH.
=2D-=20
Regards,
Mick

--nextPart1705887.PJ6AoNuzDe
Content-Type: application/pgp-signature; name=signature.asc
Content-Description: This is a digitally signed message part.

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.7 (GNU/Linux)

iD8DBQBHrvRh5Fp0QerLYPcRAqdkAKDN8FF9TcvS8DGfXJMGNvhJesIb7QCeJyh0
ZaiXnvzXOicRO8otDQUlFAM=
=YNEt
-----END PGP SIGNATURE-----

--nextPart1705887.PJ6AoNuzDe--
--
gentoo-user@lists.gentoo.org mailing list