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From: yoda@rescomp.Stanford.EDU (Terry Lee)
Newsgroups: comp.os.386bsd.questions
Subject: Re: Point to Point over Ethernet?
Date: 13 Jan 1995 22:19:21 GMT
Organization: Stanford University
Lines: 101
Message-ID: <3f6u99$5n1@nntp.Stanford.EDU>
References: <3f4f6r$gq0@nntp.Stanford.EDU> <3f6fmv$74l@sol.ctr.columbia.edu>
NNTP-Posting-Host: rescomp.stanford.edu
I apologize if this discussion has gotten in not exactly the right news group.
>: PPP allows the two point computers to share the same internet address right?
>
>Wrong. Every Internet host has at least one unique IP address.
Can you explain what this means then?: From the file 'SETUP' distributed with
ppp-2.1.1 (I got this from linux which looks like a port from BSD):
"If a host is already connected to the Internet via a LAN such as
Ethernet, then it will already have at least one IP address assigned,
which will usually be the IP address of the LAN interface. In such
cases, it is usually most convenient to use that address as the local
IP address of the PPP interface(s) on that host. This is OK because
the PPP interface(s) are point-to-point interfaces."
Later in the document it says:
"Other random points about running pppd:
- If you want the local address of the PPP link to be
different from the (first) IP address of the host, you need
to put the desired address on the pppd command line with a
colon appended."
I haven't actually tried this, so maybe I'm missing something here.
>: So if I have my BSD system running PPP to my internet service provider, I can
>: run local PPP connections to this central BSD system sharing the same IP
>: address assigned by the ISP without having to pay for class C assignment.
>: Right?
>
>Wrong. (Unless you're thinking about using something like 'term' or TIA.)
If the above configuration of PPP sharing the IP address of the host isn't
what I think it is, then I could use TIA over null modem cable right? Then
at least I can Netscape and Eudora, etc. from all the computers on my lan.
>If you:
>
>- have one BSD machine connected to the Internet via PPP
>- have other machines that you want to connected to the Internet through
> the BSD machine
>- want each machine to behave as independent Internet hosts (i.e. be able
> to telnet/FTP to each other and other Internet hosts without having to
> telnet into the BSD machine first)
>
>then you need to have the BSD machine set up as a router and each of the
>other systems needs its own IP address. You also have to ask your Internet
>service provider to set up their router (or their PPP server, or whatever)
>to forward traffic for all your machines through your BSD system. You
>may not necessarily need a whole class C subnet to do this (I'm pretty
>sure you can do it with some properly configured static routes) unless
>there are a large number of machines involved. Odds are you'll have to
>arrange for your service provider to provide DNS too.
>
>: The real question: Is there any way to accomplish this (sharing one IP
>: address accross a small lan) using ethernet as the medium instead of
>: serial lines in a star-lan configuration? Ideally, a central BSD system
>: hooked up to the internet, and Windows and Macs on ethernet accessing the
>: internet via the central server sharing the same IP address.
>
>: Possible?
>
>The "sharing one IP address" idea won't work, as I've already explained,
>but yes, you can connect all your Macs and Windows boxes to your BSD
>system via ethernet. All you need to do is plug an ethernet adapter into
>your BSD box (if it doesn't have one already). Note, however, that the
>BSD machine's ethernet interface will need yet another IP address; you'll
>have one address for ppp0 and another for ed0.
>
>If you have just the one IP address (via PPP), then this arrangement will
>let the Windows machines and Macs all talk to each other normally, plus
>they'll be able to talk to the BSD machine normally. *BUT*, in order to
>to access the Internet for things like telnet and FTP, you'll have to
>log in to the BSD machine first. The only neat thing you can do with this
>configuration is set up the BSD machine as a POP mail server. You can then
>install Eudora and/or WinEudora on the other systems. All of this assumes
>that your service provider allows you to keep your PPP line up 24 hours
>a day.
>
>Once again, if you want to connect and entire LAN to the Internet through
>a single machine with a PPP link to a service provider, you need:
>
>- valid IP addresses for all machines on your LAN
>
>- two IP addresses for the BSD machine (one for ed0 and one for ppp0)
>
>- a BSD kernel compiled with 'options GATEWAY' to enable IP packet forwarding
>
>- your Internet service provider to set up their router to forward
> packets for your LAN through your BSD machine
>
>- a nameserver -- could be yours, or you could have your ISP do name service
> for you (if you have many machines you might want your own domain, otherwise
> you can mooch of someone else's)
>
>- several large bags of cash to pay your service provider for the
> aforementioned services
>
>- a brain