91 lines
4.0 KiB
HTML
91 lines
4.0 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<!--Converted with LaTeX2HTML 96.1-c (Feb 29, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds -->
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<HTML>
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<HEAD>
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<TITLE>Running pppd</TITLE>
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</HEAD>
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<BODY LANG="EN">
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<A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node111.html">Using Options Files</A>
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<B>Up:</B> <A HREF="node107.html">The Point-to-Point Protocol</A>
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<B> Previous:</B> <A HREF="node109.html">PPP on </A>
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<BR> <P>
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<H1><A NAME="SECTION0010300000">Running pppd</A></H1>
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<A NAME="4116"></A>
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<A NAME="4542"></A>
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When you want to connect to the Internet through a PPP link, you have to
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set up basic networking capabilities such as the loopback device, and
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the resolver. Both have been covered in the previous chapters. There
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are some things to be said about using DNS over a serial link; please
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refer to the SLIP chapter for a discussion of this.
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<P>
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As an introductory example of how to establish a PPP connection with
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pppd, assume you are at vlager again. You have already
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dialed up the PPP server, c3po, and logged into the ppp
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account. c3po has already fired up its PPP driver. After
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exiting the communications program you used for dialing, you execute
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the following command:
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<pre>
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# pppd /dev/cua3 38400 crtscts defaultroute
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</pre>
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<A NAME="4125"></A>
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<A NAME="4126"></A>
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This will flip the serial line cua3 to PPP mode and establish
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an IP-link to c3po. The transfer speed used on the serial port
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will be 38400bps. The crtscts option turns on hardware
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handshake on the port, which is an absolute must at speeds above
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9600-bps.
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<P>
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The first thing pppd does after starting up is to negotiate
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several link characteristics with the remote end, using LCP. Usually,
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the default set of options pppd tries to negotiate will work,
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so we won't go into this here. We will return to LCP in more detail in
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some later section.
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<P>
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For the time being, we also assume that c3po doesn't require
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any authentication from us, so that the configuration phase is
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completed successfully.
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<P>
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<A NAME="4133"></A>
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<A NAME="4134"></A>
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<A NAME="4135"></A>
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pppd will then negotiate the IP parameters with its peer using
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IPCP, the IP control protocol. Since we didn't specify any particular
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IP-address to pppd above, it will try to use the address obtained
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by having the resolver look up the local hostname. Both will then
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announce their address to each other.
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<P>
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Usually, there's nothing wrong with these defaults. Even if your
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machine is on an Ethernet, you can use the same IP-address for both
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the Ethernet and the PPP interface. Nevertheless, pppd allows
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you to use a different address, or even to ask your peer to use some
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specific address. These options are discussed in a later section.
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<P>
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<A NAME="4139"></A>
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<A NAME="4140"></A>
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<A NAME="4141"></A>
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<A NAME="4142"></A>
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After going through the IPCP setup phase, pppd will prepare
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your host's networking layer to use the PPP link. It first configures
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the PPP network interface as a point-to-point link, using ppp0
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for the first PPP link that is active, ppp1 for the second, and
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so on. Next, it will set up a routing table entry that points to the
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host at the other end of the link. In the example shown above,
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pppd will make the default network route point to c3po,
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because we gave it the defaultroute option.<A HREF="footnode.html#4149"><IMG ALIGN=BOTTOM ALT="gif" SRC="foot_motif.gif"></A> This causes all datagrams to hosts not on your local network to be
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sent to c3po. There are a number of different routing schemes
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pppd supports, which we will cover in detail later in this
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chapter.
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<P>
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<HR><A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node111.html">Using Options Files</A>
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<B>Up:</B> <A HREF="node107.html">The Point-to-Point Protocol</A>
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<B> Previous:</B> <A HREF="node109.html">PPP on </A>
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<P><ADDRESS>
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<I>Andrew Anderson <BR>
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Thu Mar 7 23:22:06 EST 1996</I>
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</ADDRESS>
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</BODY>
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</HTML>
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