Re: OT: Setting up subnets (for dummies)

On Oct 2, 3:50 pm, J.J. O'Shea <try.not...@xxxxxxxxxxx> wrote:
On Thu, 2 Oct 2008 05:29:16 -0400, timpent wrote
(in article
<54e0e4ea-6b4c-470e-8573-2c7ac2f52...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>):

Hi all

This isn't a Mac question, but you're a friendly and knowledgable
bunch and I know you tolerate (possibly) ignorant questions!

My company (2 people) is based in a building shared with about eight
other small businesses. Anyway, the other day I noticed the other day
that I could see folders on another company's pcs, and similarly they
could see the shared folder on my Win XP laptop.

Yep... typical small biz (in)security model.



As far as I know we all connect to the router at 192.168.1.2 using the
subnet mask 255.255.255.0. (Well, we do, and I know some others do,
but the fact that I can't see all the other companies' computers makes
me suspect that they either connect through their own firewall+router
onto the main network, or they are already on a different subnet).

In this environment am I correct in thinking that a sensible solution
to making each company's computers invisible to the other companies
would be to put each company on their own subnet?

That's certainly one way.



How does one do this? Do you have to make any changes on the router
itself (Zyzel Prestige 662HW-61) or is it all set up on each PC/Mac in
the network settings? ie. can I put my own company on a subnet and
leave everyone else as they are?

You can have the router, or whatever else is serving up DHCP, split up the
existing 192.168.1.x range into a bunch of smaller ranges. If you're using
regular Classful addressing, you have a Class C range, with 254 possible IPs.
The thing is, this is all one subnet. In Classless addressing, that same
subnet is 192.168.1.0/24. If you set up a 192.168.1.0/27 Classless system,
then you have eight hosts (eight possible subnets) with 30 nodes per host
(you can have 30 devices on each subnet). If you set up a 192.168.1.0/28,
that goes to 16 hosts, with 14 nodes per host. If you have only eight
companies to account for, use the /27. f you have 9 or 10, use the /28. The
problem is, of course, that if someone needs more than 14 nodes, they're
gonna have their local network split into two or more different subnets,
which would be annoying. I don't know if that router can hack CIDR settings,
so I suspect that you'd have to turn off DHCP on the router and dedicate a
computer to being a DHCP server. Any Windows 2000, 2003, or 2008 server could
do it without any problem, and so could a OS X Server device.

It would be a whole not easier to stick an additional router between you and
the other router. However, that leads to the infamous Double NAT problem,
which can be a severe pain depending on how you set the system and what you
want to do. VPNs and stuff such as Back To My Mac will have conniptions. Web
browsing, email, and such should work without too much trouble.



There are only ever going to be a max of 12 companies in the building
each with a max of 10 computers. The person who owns the building is
not technically savvy, and I don't think the company who looks after
the router / network are particularly great either!

Okay, with a max of 12 hosts and a max of 10 nodes per host, doing a /28 CIDR
would be best. 16 possible hosts, 14 possible nodes per host. No need to get
any additional equipment if the router can hack it, and just minimal
equipment if not. You can set up a DHCP server on a regular OS X client box
without too much trouble, assuming you know the command line or can read
macosxhints or similar. I'm pretty sure that it can be done with W2K and
following, too, just that it's a pain to do it. Better yet, use some variety
of Linux. Buying one cheap box, sticking Linux on it and using it for the
DHCP server for the building would be cheaper than buying 12 routers.



Thanks for any help

Tim

--
email to oshea dot j dot j at gmail dot com.

Thanks JJ. So can you only create subnets by having another PC/Mac as
the DHCP server, or can the router do it?

Tim
.

Relevant Pages

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  • Re: OT: Setting up subnets (for dummies)
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