IP Masq+Cablemodem, need 2 nics?

IP Masq+Cablemodem, need 2 nics?

Post by Nate Cas » Sun, 28 Feb 1999 04:00:00



Hi.  I'm using MediaOne for my cablemodem service and I'm trying to
setup IP Masqerading to allow my other computer to share the
connection.  I understand IP Masqerading fairly well, but what I'm
trying to figure out is if I need to get a 2nd ethernet card for my
linux box in order for it to function correctly.  Most people do use 2
ethernet cards, but I think it's possible for me to not have to use one,
and here's why:

The cablemodem is a surfboard 1200 (sb1200), eth0 is permanantly
assigned with 192.168.100.2, even while connected (which poses problems
with some apps, but i've learned to deal with it).  Currently, I have
the cable modem plugged directly into the hub, along with my other
computers.  Right now, I can access the Internet, as well as services on
my LAN with my Linux box.  So, I don't think I need a second ethernet
card, but maybe i'm missing something.

The reason I ask is because I've tried to get it to work this way
already, but was unable to.  Either I was doing something wrong while
setting up IP Masqerading, or I indeed need another ethernet card.

Thanks in advance

 
 
 

IP Masq+Cablemodem, need 2 nics?

Post by Michael Johnso » Sun, 28 Feb 1999 04:00:00



> Hi.  I'm using MediaOne for my cablemodem service and I'm trying to
> setup IP Masqerading to allow my other computer to share the
> connection.  I understand IP Masqerading fairly well, but what I'm
> trying to figure out is if I need to get a 2nd ethernet card for my
> linux box in order for it to function correctly.  Most people do use 2
> ethernet cards, but I think it's possible for me to not have to use one,
> and here's why:

> The cablemodem is a surfboard 1200 (sb1200), eth0 is permanantly
> assigned with 192.168.100.2, even while connected (which poses problems
> with some apps, but i've learned to deal with it).  Currently, I have
> the cable modem plugged directly into the hub, along with my other
> computers.  Right now, I can access the Internet, as well as services on
> my LAN with my Linux box.  So, I don't think I need a second ethernet
> card, but maybe i'm missing something.

> The reason I ask is because I've tried to get it to work this way
> already, but was unable to.  Either I was doing something wrong while
> setting up IP Masqerading, or I indeed need another ethernet card.

> Thanks in advance

Ya
I think you will need a second network card - one to plug the cable
modem into and the other to network to the other copmputers.

That is the way I have our cable modem set up with masquerading, and it
works great.

Mike

 
 
 

IP Masq+Cablemodem, need 2 nics?

Post by Rick Onania » Tue, 02 Mar 1999 04:00:00



> The cablemodem is a surfboard 1200 (sb1200), eth0 is permanantly
> assigned with 192.168.100.2, even while connected (which poses problems
> with some apps, but i've learned to deal with it).  Currently, I have
> the cable modem plugged directly into the hub, along with my other
> computers.  Right now, I can access the Internet, as well as services on
> my LAN with my Linux box.  So, I don't think I need a second ethernet
> card, but maybe i'm missing something.

You need first to set up your own private network, seperate from theirs.
You can do this with a seperate card, or by aliasing multiple IP
addresses to your one card. If you do that, you need to plug your cable
modem into your hub, and anyone on media one (or at least, a local
section of it) can become part of your private network - your next
door neighbor only has to set his IP address to the next available
one in your intranet.

Better would be to use two ethernet cards. They're cheap now...anywhere
from five to twenty dollars. Spend the money - it's worth not getting
blamed when the kid down the street hacks Microsoft with YOUR
masqueraded IP.

  rick - a guy in search of raw (ISO) cd images of SuSE and Slackware
---------------
My opinions don't exist, and as such, are not anyone elses. I do not
represent
anyone, not even myself, and especially not my employer. Cows go moo.
---
Looking for a 1968 Camaro SS convertible, black interior, beat-up
rustbucket
that is in need of a lot of restoration and TLC. Must be cheap...I'm
broke.
---
Reply to me at either thc <at sign here> psynet <dot> net or
rick <at sign> mail <dot> artmold <dot> com

 
 
 

IP Masq+Cablemodem, need 2 nics?

Post by Kuo Sung Swe » Thu, 04 Mar 1999 04:00:00


Plus you will have a security hole.  One card for the cable modem and one
for your internal network.  You can have to different IP address and have
the linux also act as a firewall.  I don't think this feature is available
if you have the cable modem hooked up to the hub.

> Hi.  I'm using MediaOne for my cablemodem service and I'm trying to
> setup IP Masqerading to allow my other computer to share the
> connection.  I understand IP Masqerading fairly well, but what I'm
> trying to figure out is if I need to get a 2nd ethernet card for my
> linux box in order for it to function correctly.  Most people do use 2
> ethernet cards, but I think it's possible for me to not have to use one,
> and here's why:

> The cablemodem is a surfboard 1200 (sb1200), eth0 is permanantly
> assigned with 192.168.100.2, even while connected (which poses problems
> with some apps, but i've learned to deal with it).  Currently, I have
> the cable modem plugged directly into the hub, along with my other
> computers.  Right now, I can access the Internet, as well as services on
> my LAN with my Linux box.  So, I don't think I need a second ethernet
> card, but maybe i'm missing something.

> The reason I ask is because I've tried to get it to work this way
> already, but was unable to.  Either I was doing something wrong while
> setting up IP Masqerading, or I indeed need another ethernet card.

> Thanks in advance

 
 
 

IP Masq+Cablemodem, need 2 nics?

Post by Rick Onania » Fri, 05 Mar 1999 04:00:00


In addition to that, with one ethernet card, the cable company can
easily detect that you're masquerading a bunch of machines. Although
this doesn't seem to be a worry, yet, sooner or later they're going to
want to crack down on it...


> Plus you will have a security hole.  One card for the cable modem and one
> for your internal network.  You can have to different IP address and have
> the linux also act as a firewall.  I don't think this feature is available
> if you have the cable modem hooked up to the hub.


> > Hi.  I'm using MediaOne for my cablemodem service and I'm trying to
> > setup IP Masqerading to allow my other computer to share the
> > connection.  I understand IP Masqerading fairly well, but what I'm
> > trying to figure out is if I need to get a 2nd ethernet card for my
> > linux box in order for it to function correctly.  Most people do use 2
> > ethernet cards, but I think it's possible for me to not have to use one,
> > and here's why:

> > The cablemodem is a surfboard 1200 (sb1200), eth0 is permanantly
> > assigned with 192.168.100.2, even while connected (which poses problems
> > with some apps, but i've learned to deal with it).  Currently, I have
> > the cable modem plugged directly into the hub, along with my other
> > computers.  Right now, I can access the Internet, as well as services on
> > my LAN with my Linux box.  So, I don't think I need a second ethernet
> > card, but maybe i'm missing something.

> > The reason I ask is because I've tried to get it to work this way
> > already, but was unable to.  Either I was doing something wrong while
> > setting up IP Masqerading, or I indeed need another ethernet card.

> > Thanks in advance

--
  rick - a guy in search of raw (ISO) cd images of SuSE and Slackware
---------------
My opinions don't exist, and as such, are not anyone elses. I do not
represent anyone, not even myself, and especially not my employer.
---
Looking for a 1968 Camaro SS convertible, black interior,
beat-up rustbucket that is in need lots of restoration and TLC.
---
Reply to me at either thc <at sign here> psynet <dot> net or
rick <at sign> mail <dot> artmold <dot> com
 
 
 

1. IP Masq slow with Cablemodem

Hi,
        I've got an IP Masquerading setup here that works just fine,
but things are pretty slow and I'm getting a wierd message on the
Linux machine.
        Running RH5.2 on a P100/32m, two ISA network cards, and all
the IP Masq stuff setup just fine.  Have a cable modem plugged into
the Linux box, and two Win95 machines plugged into a hub then into the
Linux box.
        I get long pauses (30-60 seconds) on the Win95 machines while
on the Net (downloading mail, newsgroup headers, etc), and the speed
is noticably slower when things are going.  Also, on the Linux box,
when I'm at the command prompt (no X running), I get a repeated
message:

eth1: XMT status = 0xffff8841

        Is that normal (doesn't sound right to me)? Is something wrong
with the way my network cards are setup? I've got an Intel
EtherExpress Pro 10+ and a 3Com 509b, both drivers compiled into the
kernel. eth1 is the Intel card going to the hub.
        Any help would be greatly appreciated.

Roger

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