[plug] Query about gateway computer settings

[Jon L Miller]

See below

-----Original Message-----
From: plug-bounces at plug.org.au [mailto:plug-bounces at plug.org.au] On Behalf
Of Bret Busby
Sent: Thursday, 24 March 2011 3:05 AM
To: plug at plug.org.au
Subject: [plug] Query about gateway computer settings

Hello.

A couple of, or a few, weeks ago, we had an electricity supply
failure, and restoration of the supply was bodgy, with only half the
lights working, and anything drawing more electricity, shutting down
again after a few minutes. That included the UPS's that regulate the
electricity supply for the LAN computers.

When the electricity supply was properly restored, we could not
connect to the Internet, via the ADSL modem (a Speedstream 4200
modem), and I could not ping the NIC that went from the gateway
computer to the modem. After a while, I could not ping the NIC that
connected the gateway computer to the LAN.

At that stage, the gateway computer was running Smoothwall 2.0 Express.

When I phoned the ISP, they got me to do a factory reset on the modem,
that erased all of the modem settings., then, when it came to
configuring the modem, they basically said "Get stuffed - we don't
provide support for anything other than Windows running Internet
Explorer, and you shouldn't be using a firewall to access the
Internet".

I subsequently tried installing Smoothwall 3.0 Express, but could not
get it working.

I then installed Debian 5 on the gateway computer, to later set up a
firewall using fwbuilder.

But I could not get the system to work with the NIC's, and could not
ping either NIC, from my workstation on the LAN.

So, I took the Gateway computer to its manufacturer, and got the two
NIC's checked (and subsequently found that it also has an inboard NIC,
which is now disabled).

The computer manufacturer got the two NIC's working with Debian 5, and
I brought the computer home, and reconnected it. The technician
advised me that having a firewall computer, requires static IP
addresses.

I spoke to the highest level support people at the ISP, and the
Customer Relations department at the ISP, and the policy of the ISP,
is that no-one who connects to the Internet, should be using a
firewall, and Linux users can go and get stuffed.

With a bit more messing around, without much success with the above
ADSL modem, we got a DHCP connection working with a Windows 7 netbook,
and a Netgear DG834GSP ADSL modem, which incorporates a 4 port router.

I have since got the gateway computer communicating with the LAN, and
with the modem, and I can ping the LAN NIC on the gateway computer,
and I can ping the NIC that is connected to the modem, both from my
workstation within the LAN, but I cannot ping the modem from my
workstation.

The LAN uses the IP address range 192.x.x.x, and a LAN (?) involving
the gateway computer NIC that is interfaced to the modem, and a couple
of computers, via a switch, and the ADSL modem, uses the 10.x.x.x IP
address range.

Jlm> so what you are saying is that you cannot ping the 10.x.x.x network
from the 192.x.x.x network? If this is true you need to check your firewall
and make sure you are routing packets from the 192.x.x.x to 10.x.x.x.

The ADSL modem is set up for DHCP, and I found in the Admin Guide for
the ADSL modem (the router one), a facility for reserving specified IP
addresses, so that it is (to me) a bit like having static IP addresses
within a DHCP facility.


So, I have a reserved IP address for the NIC on the gateway computer,
that interfaces with the modem, and I have that IP address specified
as a static IP address in the NIC configuration of the gateway
computer.

I have got the gateway computer set up, so that I can go out on the
Internet, via the ADSL modem/router, and I have used that to perform a
system update on the gateway computer.

On both NIC's on the gateway computer, I have the IP address of the
ADSL modem, specified as the IP address of the DNS server (using
System -> Network -> DNS).

Jlm> why are you using the same ip address on both NIC's? If the gateway
computer only has 2 nics, then one needs to be configured for internal LAN
192.x.x.x and connected to a switch or hub and the other for the external
LAN 10.x.x.x and this is connected to the adsl modem.  Routing will need to
be setup as a static route from the 192.x.x.x to 10.x.x.x.



On my workstation, I have tried using the IP address of the LAN NIC on
the gateway computer, as the DNS server, and I have tried using the IP
address of the NIC on the gateway computer, that interfaces to the
ADSL modem, as the DNS server, and I have tried using the IP address
of the ADSL modem, as the DNS server, but I cannot get to the modem
(any of pinging the modem, or the web interface for the modem, or,
going past the modem, out onto the Internet), from my workstation.

Jlm> DNS services will depends on if you are exchanging information upstream
or just within the local LAN.  If using just the local LAN the DNS server
can and should reside on the 192.x.x.x ip space, whereas if the DNS data is
being exchanged with an upstream DNS master server then the put the ip
address of the DNS server on the 10.x.x.x network and do a NAT for 10.x.x.x
to the ADSL modem.  

When the gateway computer was running Smoothwall 2.0 Express, the
using the IP address of the LAN NIC on the gateway computer, as the IP
address for the DNS server, had worked in enabling access to the
Internet.

So, after all of that, what else do I need to do, assuming that it
lies in configuring the gateway computer, to allow computers within
the LAN, to reach the ADSL modem, both for using the web interface for
configuring the modem, and, more importantly, to go out onto the
Internet?

Thank you in anticipation.

-- 
Bret Busby
Armadale
West Australia
..............

"So once you do know what the question actually is,
 you'll know what the answer means."
- Deep Thought,
 Chapter 28 of Book 1 of
 "The Hitchhiker's Guide to the Galaxy:
 A Trilogy In Four Parts",
 written by Douglas Adams,
 published by Pan Books, 1992

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