INTERIM SUMMARY: Small network onto Internet

From: Terence P. Ma (tpm-sprl!tpm@uunet.UU.NET)
Date: Tue Aug 06 1991 - 19:06:52 CDT

Due to a personal emergency, I have to go out of town starting tomorrow
(8/7) and thus will not be able to give a complete summary of the responses
until some time next week. In the meantime ....

I asked:

> I have 2 PCs that I have on a small network with my Sun SPARCStation. I
> have been using a local IP number that I invented. Now, I am going to get
> connected onto Internet, and will serve as a host for lots of PCs in my
> department. However, the problem is that I will be given a "real" IP number.
> But only one number.
> The idea is that everyone will connect into me, and then I connect out to
> the world. I don't understand how I can do this with only one ethernet card
> on my Sun. Furthermore, when I tried to set up my Sun with my "real" IP
> number, I can't get my PCs to telnet in (I use both PC-NFS from Sun and NCSA
> Telnet).

I should have said that our medical center is going on Internet and has a
class C number (192.42.101) and I have been assigned the number
( It was told to me by the Administrator for Internet that
since we only have a restricted number of numbers available, that he wanted
people to be able to log into one of four machines on campus (mine being
one) and then connect to Internet through those machines. The local
networks run through each of those machines would NOT be on Internet, but
can be handled through the same transciever as the Internet (I didn't think
this was true, but I know little-to-nothing about networks).

Thanks to all who have responded so far. I true summary will be posted
after I get back from my trip.


***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** *****

From: Andrew Luebker <uunet!!aahvdl>

I only see two alternatives:

  1) Get "genuine" IP addresses for all the PC's, or
  2) Keep your bogus addresses on the PC's and put a ROUTER between
     them and SPARCstation. You might be able to add another Ethernet
     card to the SPARCstation and make it into the ROUTER machine, but
     I can only vouch for older Sun-3 machines! Otherwise, you could
     buy a turbo PC/AT machine and a couple Ethernet cards, and run the
     "PC-ROUTER" software available via anonymous FTP. That MIGHT work...

We also use both PC-NFS and NCSA Telnet here. In either case, you need
tell the micros about a gateway machine. It probably should be in your
bogus domain, but you might be able to convince the micros to directly
contact the "real" SPARC machine. Possibly need to twiddle with the
netmask to fool those machines...

***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** *****

From: uunet!!ho (Hilarie K. Orman)

You will have to have some machine that has two interfaces: one to your
ethernet and one to the Internet. What sort of connection are you getting?
Perhaps you are getting a SLIP connection over a serial port? In that
case, you will use your "real" internet number for the serial port
interface, and you can continue to use your "fake" numbers for the
ethernet port and the PC's. However, you can easily get a "real" class C
network number from and join the world of
the legitimate. This is a Good Idea.

I'm no expert - I'm just trying to help you in case the real experts are
slow in answering.

***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** *****

From: uunet!!geertj

Each device that has an ethernet plug (PC and SUN) needs its own IP address.

I'll provide you (and your network admins? :-) with a paper that you
might find interesting. It is compressed.

Hope it helps, Geert Jan

(Note: for some reason I haven't been able to uncompress the file with my
"uncompress" command. Hopefully I can summarize some highlights when I post
my full summary. TPM)

***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** *****

From: uunet!!klamer (Klamer Schutte)

PS This mail seemed to bounce so i resend it -- Klamer

How are you connected to the internet? By ethernet? Or different?
Your internet connection has a IP address. Your ethernet address has an IP
address. If these connections are the same (i.e. you want to run your
sun+pc network on the same ethernet as your internet connection) you are
doing it all wrong. If you internet connection is different (another ethernet?
that does mean another ethernet interface, or an X25 connection) than that
other interface (ethernet, X25, ...) has the other (official) IP address.

So your setup will be:
le0 (invented number, on local ethernet)
le1 (official number, on internet)

le1 probably is different for you. So is, and certainly

Note that your sun will automatically route, and the rest of the world won't
the addresses you invented. Think about getting an official address for your
subnet as well.

Hope this clarifies,


***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** *****

From: uunet!!jba (Jan B. Andersen)

(Corresponding at this time, will summarize his help as soon as I am back.)

***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** *****

From: uunet!!pomeranz (Hal Pomeranz)

Sounds to me like each PC on your network is going to have to have its
own "real" internet number. The reason the PCs can't reach your
workstation is that they still have "fake" numbers and don't know how to
reach machines with "real" addresses (even though they physically reside
on the same wire).

***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** *****

From: Chris Kondellis <uunet!!ckon>

Buy another ethernet card for your SUN in order to create your private (non-
Internet) network. Your SPARC then will serve as a router!

Antonis /

***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** ***** *****

From: uunet!!kncarp (Kevin N. Carpenter)

I don't think you can do it. It sounds like you are a prime candidate for a
registered Class C subnet. Who is giving you a single TCP/IP node number?
Somebody internal? If so, do you have enough weight to request a subnet range?

If you have any slots open in your Sun, you could buy a second ethernet
adapter. Then you could make your box a gateway. It would still be messy
not to have all of the boxes using registered numbers, but it could be done.

This archive was generated by hypermail 2.1.2 : Fri Sep 28 2001 - 23:06:20 CDT