[Coco] OT: Networking problem

[Gene Heskett]

On Wednesday 28 November 2012 20:09:51 David Hazelton did opine:

> Not to ask a stupid question, but Does your ISP allow their DSL Modem to
> have multiple IPs.
> Working for Comcast, the cable modem only passes 1 IP.  so what you are
> doing is not possible by going off the dsl modem.

Several machines on one outside IP address is absolutely not a problem 
David.  There is no crosstalk between the machines even when the 2 out in 
the shop are both installing the latest updates to the 10.04.4 installs I 
have on 4 machines here, and which could just as easily be 253 machines.

Its called NAT, for Native Address Translation.  If your router cannot do 
that, toss it in the bin and get one that will as its been a atd feature of 
most for over 15 years that I know of.

I've had 6 or seven in that position between the cable or dsl modem and an 
8 port switch for well over a decade now.  The best I have found are all 
running some version of dd-wrt for software, and am currently using a 
Buffalo NFinity Hi Power, which comes with a broken, customized version of 
dd-wrt.  But their banners covered up some of the functions, which was the 
brokenness so it got reflashed to the real dd-wrt.

All machines on the on-property net, coming off that 8 port switch, are 
using hard coded addresses set in 192.168.xx.xx range, set the /etc/hosts 
file except the lappy, a file that is common to all the machines, with only 
that machines hostname differentiating between them.

The lappy gets an address from the dhcp server in the router.  And it all 
Just Works(TM).  Any machine plugged into the switch can do anything it 
wants in the way of net access, with complete isolation between the 
machines.

OTOH NFS mounts between the main 3 machines works as expected, as does ssh 
access between them.

> On 11/26/2012 6:59 PM, Aaron Banerjee wrote:
> > This is a little off-topic, but is something eople here probably have
> > more experience with than I do.
> > 
> > I'm trying to "partition" off my network into multiple networks (e.g.
> > for experimental purposes/parental control/etc).  I have a DSL modem
> > and a router.  I thought the following configuration would work, but
> > it doesn't.
> > 
> >                       ----
> >                       
> >                       |   | <--------------------------> {other device
> > 
> > with static 192.168.1.n IP}
> > {internet}  <-------> |   |   "1.2.168.1.x" network
> > 
> >                       |   |    static IPs                ----
> >                       |   | 
> >                       |   | <--------------------------> | R |
> > 
> > "192.168.0.y" network (using DCHP from router)
> > 
> >                       ----                               | O |
> >                    
> >                    DSL Modem                             | U |
> > 
> > <------------> device 1
> > 
> >                   192.168.1.1                            | T |
> > 
> > <------------> device 2
> > 
> >                                                          | E |
> > 
> > <------------> device 3
> > 
> >                                                          | R |
> >                                                          
> >                                                          ----
> >                                             
> >                                             192.168.1.101 /
> >                                             192.168.0.1
> >                                             
> >                                                    netmask 255.255.0.0
> > 
> > Sorry about the '80s era graphics, but I didn't want to have to attach
> > a file -- and besides, I'm from the '80s era (at least when it comes
> > to computers).
> > 
> > 1.  I'd like to have the device 1,2,3 be able to "ping" or summarily
> > see the modem.  I think this should work, but it doesn't.  What did I
> > do wrong (or not do right)?

You'll need a secondary interface, setup on the same hardware, something 
like an eth0.1.  Its in the man pages and a bit lengthy for a mailing list 
post.

As for a connection between the "0.xx addresses, and the "1.xx', look up 
the keyword "bridge", which will wire up a connection between those 2 nets.
 
> > The router's address to its clients is 192.168.0.1.  It is statically
> > set to 192.168.1.101 for purposes of the modem (which doesn't use
> > DCHP).  The router then uses its own DCHP to doll out addresses to its
> > client as it sees fit (in particular it starts with .100).
> > 
> > For experimental purposes, I took down the firewall completely in
> > order to eliminate that as a source of the problem.  I'm getting a "no
> > route to host" when I ping 192.168.1.1 from the devices on the "0" net
> > (e.g. device 1, 2, or 3).  I don't have "ping" blocked at the modem or
> > router just for good measure, and don't think I'm masking out the
> > "1".  Even a few desperado attempts using DMZs didn't work, and
> > eventually messed up my network until I could undo all that I had
> > done.
> > 
> > I'm obviously missing something very simple and elementary and will
> > probably kick myself when someone points it out to me.  I just haven't
> > done this type of thing in a long while.
> > 
> > Thanks in advance for your help.
> > 
> > - Aaron
> 
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> Coco at maltedmedia.com
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Cheers, Gene
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