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Re: two networks sharing one router


On Thu, 9 Oct 2003 17:25:46 +0300 "M. Civan CAMKIRAN" <civan@ads.com.tr>

> I have two networks which belong to two different companies in a
> building and one broadband internet connection. I decided to buy an
> inexpensive 4 port router and plug each hub to 2 of the 4 ports on
> this router. Questions are:

Please define "inexpensive 4port router":

- a cheap (DSL) router with builtin 4port switch/hub, thus effectively
  only a 2port router with the second port multiplied by an internal
  hub/switch (usually in the $50+ range)

- a router with 4 full/independent LAN/WAN interfaces (e.g. Cisco 26xx,
  usually above $1000)

> 1. Is it possible to have both networks use the same internet
> connection in this way?

Yes - but usually the cheap DSL routers don't allow multiple independent
networks on the inside interface/hub.

> 2. Is it possible to prevent the computers see the other network's
> computers? If yes, how?

Full router: yes, just set the proper ACLs.
DSL router with hub/switch: no

Depending on your brand, cheap broadband routers MIGHT be able
(depending on built-in options) to do just routing ethernet/ethernet. If
so, you'd need two more routers, each one hiding the individual company
network, then connecting to the common DSL router. ASCII art below:

   |       |
   |       |
 Rou1     Rou2
   |       |
   |       |
 --+--   --+--
  LAN1    LAN2

You'd be probably better/cheaper off with a multiport (!) DSL-enabled

Good luck!

Volker Tanger

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