Slightly OT: DSL modem is a router ?

  • Thread starter Thread starter johns
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johns

My desktop pc is connected via network cable to a
DSL modem which goes out on the phoneline at 768 mb.

If I open a command window and type ipconfig /all, I can
see the MAC address of my network card in the desktop,
and I can also see the ip-address it is using. The ip-
address is a 192.x.x.x which I was told is given by
the DSL modem itself .. rather than being given by the
AT&T server / service. The DSL modem is externally
registered with AT&T, and uses an external protocol
to talk out.

My question: I would like to tie in another pc / laptop
to that DSL modem for online banking and other
critical data, and then shut that laptop down and
keep it secure .. and offline. Can I simply splice a
second network cable from the single port on the
DSL modem to the laptop, and have that DSL
modem issue an ip-address to the laptop? Or do
I have to shut the DSL modem down, and hook it
to the laptop and reboot to get an ip-address for
the laptop to talk out ? I don't mind doing that
because I won't do it more than about once a
week. I just don't want to go buy $$$ stuff I don't
really need. One of the Geek Squad said I needed
a router between the 2 boxes and the DSL modem.
I don't think so. I think the DSL modem is already
a router ( since the 192.x.x.x ) is not a real
external ip-address.

johns
 
johns said:
I would like to tie in another pc / laptop
to that DSL modem for online banking and other
critical data, and then shut that laptop down and
keep it secure .. and offline.
Click to expand...
One of the Geek Squad said I needed
a router between the 2 boxes and the DSL modem.
I don't think so. I think the DSL modem is already
a router ( since the 192.x.x.x ) is not a real
external ip-address.
Click to expand...

Just in case you do not get a satisfactory answer, you might also
try asking the experts in UseNet *dcom* groups.

Still inline skating?
Chad Hedrick, King of inline skating now kicking butt on ice, goes
for the Olympic Gold Saturday in men's 1500 meter ice speed skating.
He got bronze in yesterday's 1000 meter race, will be his 5th Olympic
medal. Apolo Ohno is another inline skater turned ice butt-kicker.
 
johns said:
My desktop pc is connected via network cable to a
DSL modem which goes out on the phoneline at 768 mb.

If I open a command window and type ipconfig /all, I can
see the MAC address of my network card in the desktop,
and I can also see the ip-address it is using. The ip-
address is a 192.x.x.x which I was told is given by
the DSL modem itself .. rather than being given by the
AT&T server / service. The DSL modem is externally
registered with AT&T, and uses an external protocol
to talk out.

My question: I would like to tie in another pc / laptop
to that DSL modem for online banking and other
critical data, and then shut that laptop down and
keep it secure .. and offline. Can I simply splice a
second network cable from the single port on the
DSL modem to the laptop, and have that DSL
modem issue an ip-address to the laptop? Or do
I have to shut the DSL modem down, and hook it
to the laptop and reboot to get an ip-address for
the laptop to talk out ? I don't mind doing that
because I won't do it more than about once a
week. I just don't want to go buy $$$ stuff I don't
really need. One of the Geek Squad said I needed
a router between the 2 boxes and the DSL modem.
I don't think so. I think the DSL modem is already
a router ( since the 192.x.x.x ) is not a real
external ip-address.

johns
Click to expand...

The 192.x.x.x address could have been assigned by the laptop
itself if you have set its network port for a static
address. But more likely, the laptop is set as a dhcp client
and got that address from the modem. Maybe the modem is
willing to deal out more ip addresses ... or not. Depends
on how the manufacturer set it up in firmware. Instruction
book should tell you.

Assuming the modem is indeed willing to serve more than one
ip address, a network switch is the minimum hardware
addition to create your lan. Splicing a second cable into
the port will not work. Using a router instead would also
work: the router includes the switch. It also provides a
firewall to keep the bad guys out of your network.

Bryce
 
Still inline skating?

I switched to quads. Geeze those things are crap compared
to inlines, but I wanted to see if I could conquer a quad and
impress the ladies at a local rink. Seems the inlines are dead
in the water these days. I can't find a good pair in any of the
sport shops .. that will go in the street. We have a skate park
but I'm too old to hang out there. So the quads will have to
do, and I'm about the only "quad skater" with all the turns
front and back .. and even a few decent jumps.
Chad Hedrick, King of inline skating now kicking butt on ice, goes
for the Olympic Gold Saturday in men's 1500 meter ice speed skating.
He got bronze in yesterday's 1000 meter race, will be his 5th Olympic
medal. Apolo Ohno is another inline skater turned ice butt-kicker.
Click to expand...

Yep. Us old guys are still out there. They'll have to haul me away
in a garbage truck before I stop skating. I'm on the ice too. Have
all the jumps and moves, and several dance partners in the
compulsory ice dances ... Dutch Waltz, Cha-Cha. There are
7 ladies here looking for dance partners.

johns
 
Assuming the modem is indeed willing to serve more than one
ip address, a network switch is the minimum hardware
addition to create your lan.  
Click to expand...

Thanks. I'll try to find one for sale. Geek wanted to
sell me a router, but I think it will conflict with the
DSL modem, and then I'll be stuck with a router.
I actually once tried splicing 2 net cables into the
same port on a commercial switch at my job.
It worked fine, but the Management System
got confused. It still worked, but I'm not going
to hack my bank account system. Not smart !

johns
 
johns said:
Thanks. I'll try to find one for sale. Geek wanted to
sell me a router, but I think it will conflict with the
DSL modem, and then I'll be stuck with a router.
Click to expand...

A router is not going to conflict with that modem, whatever it is.

You should name the brand and modelno of your modem if we are going to
debate the fine points of choosing between a router and a switch
including the economics of which is more likely to be on sale. Or even
a hub if you aren't planning on using two machines at a time.
 
Andy said:
If your modem has only one LAN connector, then it probably does not
contain a router. Conversely, a router typically has multiple LAN
connectors.
Click to expand...

You can find a combined ADSL modem/router with only
one LAN side Ethernet connector on it. One benefit
of the router function, is there is no PPPoE or PPPoA
to terminate - the connector is a real LAN connector
instead. Just plug and go (after entering your ADSL
username and password for PPP login).

http://www.speedtouch.ca/pdf/Datasheet_516v6.pdf

Paul
 
Andy said:
If your modem has only one LAN connector, then it probably
does not contain a router. Conversely, a router typically
has multiple LAN connectors.
Click to expand...
My Motorola SB5100 cable modem has only one LAN port. It
does routing. I just tried it by connecting the modem to a
switch and then connecting the switch to two computers, both
set up as dhcp clients. The two machines simultaneously
obtained different ip addresses in the 76.189.x.x range and
both were able to access the internet at once. The router
that I normally use was disconnected and powered down, so no
tricks being done here.

I also have a spare PC fitted with two NICs and set up as a
stand-alone Linux router/firewall. The modem gets connected
to one port and the other goes to a switch that interfaces
with my network. I use it when I need to connect a Windows
machine to the internet (as in income tax time). I trust it
more than the firewall built into my traditional home
router.

Routing needs a switch somewhere, but it need not be built
into the box where the routing happens.

A modem may have more smarts than we think.
 
Mike said:
A router is not going to conflict with that modem, whatever it is.

You should name the brand and modelno of your modem if we are going to
debate the fine points of choosing between a router and a switch
including the economics of which is more likely to be on sale. Or
even a hub if you aren't planning on using two machines at a time.
Click to expand...

Most modem hardware, be it DSL or Cable has the "ability" to provide more IP
address values than a typical home could use. With that said, the provider
limit the box to only one address any other value they choose to configure
into it from the host end.

One quick and dirty test to see if the unit is set to provide more than one
address is to take your working system and note the IP address of the PC.
Then unplug only the Ethernet of the PC and plug in another PC. Either
reboot that PC or do an ipconfig /release followed by ipconfig /renew in a
command window and then see what IP address the second machine is assigned.
If the second PC gets a different IP address than the first you should be
good to go with just a switch.

The trick is to not power cycle or reset the providers box during the above
test. If it takes a power reset of the providers box just to get assigned
an ip address other than 169.xx.xx.xx then the odds are the box is set to
only give you one address and you would need to get your own router rather
than a switch.

Visit the second hand computer shops and you should be able to pick one up
for $10 or less. Just make sure to power it on at their place in case the
power transformer they have is actually for something else...

Here is a link to a switch that is currently on sale for about $12. new at
newegg.com.
http://www.newegg.com/Product/Product.aspx?Item=N82E16833320044&cm_re=switch-_-33-320-044-_-Product
 
Thanks. I think what also "might" work .. and I've actually
used one on a wall plate .. is called a port expander. They
are really cheap, but I haven't seem them in stores.

johns
 
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