RE: Network addressing

["Mike Lieberman" <Mike@netwright.net>]

Kaa wrote:
>
>
> I have two machines plugged into a cable modem. Both have IP
> addresses
> provided by the ISP. One is 24.6.xxx.xxx, and the other is
> 24.5.xxx.xxx.
> Theoretically that's all fine 'cause 24. is an A class
> network. However the
> ISP says that the netmask for these addresses should be
> 255.255.255.0, that
> is, they are subnetting their class A net. And herein lies
> the problem:
> looking at their netmask the machines believe they are on
> separate networks
> and so to talk to each other they need the upstream machines
> -- the gateways
> for each of them -- to be up. That doesn't happen all the
> time and anyway, I
> want these two machines to be able to talk to each other
> without involving
> the upstream machines at all.
>
> So, my question is: can I simply set the netmask to 255.0.0.0
> on both of
> them and put appropriate entries into the /etc/hosts file? Is
> this likely to
> break anything? Alternatively, can I use arp to specify the
> Ethernet address
> - IP address correspondence, or something will get confused?

Neither plan is good. Please remember that cable modems are broadcast
networks. Your ISP, @Home, uses that Class A as subnetted Class C's for good
reason.  If @Home is unwilling to assign you two addresses in the same
subnet (I assume you asked, right?) there are a number of two to deal with
this.

Option 1: Two NIC's.
	Add a second NIC in each computer and assign a ambiguous (private) IP
network. The classic is 10.0.0.0. Look at RFC
ftp://ftp.internic.net/policy/rfc1597.txt

Option 2: Set one box up as a Proxy Server
	That box gets two NIC's, the other one. You use ONE IP address. Your ISP
sees only one computer. Use the private IP behind the firewall.


> And a semi-related question: on a pure Win98 machine, how do
> you find out
> the Ethernet address of the NIC card? I tried looking through
> the registry,
> but didn't find anything that looked right.

There is a netstat utility, I'm not sure if it's in the Resource Kit or
ships with the product.


/* Mike Lieberman                            Mike@NetWright.Net */
/*                         President                            */
/*                       Net Wright LLC                         */
/*                   http://www.netwright.net                   */
/*                 Voice and Fax: 307-857-1053                  */