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Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.mira.net.au!news.netspace.net.au!serval.net.wsu.edu!netnews.nwnet.net!oracle.pnl.gov!osi-east2.es.net!lll-winken.llnl.gov!sol.ctr.columbia.edu!startide.ctr.columbia.edu!wpaul From: wpaul@ctr.columbia.edu (Bill Paul) Newsgroups: comp.os.386bsd.questions Subject: Re: Point to Point over Ethernet? Date: 15 Jan 1995 04:45:19 GMT Organization: Columbia University Center for Telecommunications Research Lines: 101 Message-ID: <3fa98v$9v8@sol.ctr.columbia.edu> References: <3f4f6r$gq0@nntp.Stanford.EDU> <3f6fmv$74l@sol.ctr.columbia.edu> <3f6u99$5n1@nntp.Stanford.EDU> NNTP-Posting-Host: startide.ctr.columbia.edu X-Newsreader: TIN [version 1.2 PL2] Daring to challenge the will of the almighty Leviam00se, Terry Lee (yoda@rescomp.Stanford.EDU) had the courage to say: : 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." I think this is saying that if your system has an ethernet interface already in it, and you decide to add a PPP interface, then you can give the local side of the PPP interface the same address as the ethernet interface. This strikes me as somewhat bogus; I *think* it is possible to ifconfig two interfaces (say ppp0 and ed0) with the same IP address, but I've never found a circumstance where doing that would be beneficial. And it won't do *any* good in terms of actually using both interfaces at the same time: you must have seperates addresses for each interface so that the routers on your network can route traffic accordingly. And this has nothing to do with your original question. : 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. I haven't tried this either... in many cases your PPP server will know what your PPP interface's address is, and it will tell your PPP client when the connection is first established. But you certainly are allowed to specify the address on the command line if you want. This doesn't change the fact that you still need two IP addresses if you want to have both ethernet and PPP interfaces on your machine. And it also doesn't change the fact that this still has nothing to do with your original question. : >: 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. It isn't what you think it is; but you're on the right track with TIA. Assuming you had enough serial ports, you could in fact connect a bunch of TIA clients to your BSD box and use Netscape, Mosaic or whatever through its PPP connection to the Internet. Unfortunately, you're limited by the number of available serial ports, and I don't think TIA works over ethernet (unless there's some trick I don't know about, or unless somebody decides to modify TIA to do this). If it *did* work over ethernet, then you could create a local network (with dummy IP addresses that you could assign yourself) and use your BSD machine as a gateway to the Internet. There's still a limit inherent in this though, since there's a fixed number of TCP ports available on each host (65536, of which 1024 are privileged), but you'd probably end up saturating your PPP link before you ever came close to using them all. (As an aside, if your client machines used Linux of *BSD, then you could use 'term' instead of TIA, and then you *could* use ethernet.) While this is technically possible, there might be some legal problems involved too: I happen to know that some Internet service providers take a very dime view of people doings things like this; usually when you purchase SLIP/PPP service for one system, they don't expect you to use it to link a whole slew of machines to the Internet with it. (They generally want you to buy a decidated line for this sort of thing.) Be especially careful if you're paying for 'personal' service: you'll be violating your agreement with your provider if you have several people using your supposedly 'personal' connection at the same time. -Bill -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~T~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Bill Paul (212) 854-6020 | System Manager Work: wpaul@ctr.columbia.edu | Center for Telecommunications Research Home: wpaul@skynet.ctr.columbia.edu | Columbia University, New York City ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The Møøse Illuminati: ignore it and be confused, or join it and be confusing! ~~~~~~~~ FreeBSD 2.1.0-Development #0: Fri Jan 13 22:04:07 EST 1995 ~~~~~~~~~