crossover cables / OpenBSD crashes

[mark at buttery.org (Mark J. Dulcey)]

Seth Gordon wrote:
> 
> My home network used to look like this:
> 
>                     ---------------
>    --------------   |W  Linksys  L|   -------   -----------
> ---| DSL router |---|A  firewall A|---# HUB |---| petunia |
>    --------------   |N    box    N|   -------   -----------
>                     ---------------   | |   |
>                                       | |   |
>                          ----------------  ------------
>                          | horse-nettle |  | eggplant |
>                          ----------------  ------------

I think I'd return to this original setup, and configure the Linksys box
to forward the DNS ports to horse-nettle. That way, you get to keep the
firewall capability of the Linksys, and still run a DNS server that is
visible to the outside world.

> Unfortunately, when I try to run a DNS server on horse-nettle,
> machines outside the firewall can't access it.  No problem, I think --
> I'll just rearrange the network so it looks like this:
> 
>                                        --------------
>    --------------   ----------------   |W Linksys  L|   -------
> ---| DSL router |---| horse-nettle |---|A firewall A|---# HUB |
>    --------------   ----------------   |N   box    N|   -------
>                                        --------------   |     |
>                                               -----------     |   
>                                               | petunia |     |
>                                               -----------     |
>                                                    ------------
>                                                    | eggplant |
>                                                    ------------
> 
> QUESTION THE FIRST: In this configuration, which connections, if any,
> require crossover cables?  (In the previous configuration, nothing had
> crossover cables.  The Linksys has a button you can push depending on
> whether you're connecting its LAN port to a hub or directly to another
> machine.

Setting things up this way really won't work; horse-nettle will have to
do NAT here, not the Linksys. If you really want to set things up like
this, the Linksys isn't really doing anything for you any more, so you
might as well get rid of it.

If you can get a second IP address from your ISP, another alternative
would be to have horse-nettle and the Linksys in parallel (not series as
they are drawn above) on the WAN; that is, you would plug a hub into the
DSL router, and connect both to it.

As for crossover cables: you would need one between horse-nettle and the
Linksys. You probably don't need one between the DSL router and
horse-nettle, since most DSL routers are built with their ports crossed
over already (that is, you use a straight-through cable to connect one
to a computer, and a crossover cable to connect it to a hub). I can't
say whether this is true of your hardware without knowing what you have.
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