<HTML ><HEAD ><TITLE >Setting up the PPP options files</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.52"><LINK REL="HOME" TITLE="Linux PPP HOWTO" HREF="index.html"><LINK REL="UP" TITLE="Setting up a PPP server" HREF="ppp-server.html"><LINK REL="PREVIOUS" TITLE="Setting up standard (shell access) dialup." HREF="x1547.html"><LINK REL="NEXT" TITLE="Setting pppd up to allow users to (successfully) run it" HREF="x1569.html"></HEAD ><BODY CLASS="SECT1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" ><A HREF="http://www.linuxports.com/howto/ppp" TARGET="_top" >Linux PPP HOWTO</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="x1547.html" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 28. Setting up a PPP server</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="x1569.html" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="AEN1552" >28.5. Setting up the PPP options files</A ></H1 ><P >You will need to set up the overall <TT CLASS="LITERAL" >/etc/ppp/options</TT > with the common options for all dial up ports. The options we use are:-</P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><PRE CLASS="PROGRAMLISTING" >asyncmap 0 netmask 255.255.254.0 proxyarp lock crtscts modem</PRE ></TD ></TR ></TABLE > </P ><P >Note - we do NOT use any (obvious) routing - and in particular there is no defaultroute option. The reason for this is that all you (as a PPP server) are required to do is to route packets <I CLASS="EMPHASIS" >from</I > the ppp client out across your LAN/Internet and route packets <I CLASS="EMPHASIS" >to</I > the client from your LAN and beyond.</P ><P >All that is necessary for this is a host route to the client machine and the use of the 'proxyarp' option to pppd.</P ><P >The 'proxyarp' option sets up (surprise) a proxy ARP entry in the PPP server's ARP table that basically says 'send all packets destined for the PPP client to me'. This is the easiest way to set up routing to a single PPP client - but you cannot use this if you are routing between two LANs - you must add proper network routes which can't use proxy ARP.</P ><P >You will almost certainly wish to provide dynamic IP number allocation to your dial up users. You can accomplish this by allocating an IP number to each dial up port. Now, create a <TT CLASS="LITERAL" >/etc/ppp/options.ttyXX</TT > for each dial up port.</P ><P >In this, simply put the local (server) IP number and the IP number that is to be used for that port. For example</P ><P > <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><PRE CLASS="PROGRAMLISTING" >kepler:slip01</PRE ></TD ></TR ></TABLE > </P ><P >In particular, note that you can use valid host names in this file (I find that I only remember the IP numbers of critical machines and devices on my networks - names are more meaningful)!</P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="x1547.html" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="x1569.html" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Setting up standard (shell access) dialup.</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ppp-server.html" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Setting pppd up to allow users to (successfully) run it</TD ></TR ></TABLE ></DIV ></BODY ></HTML >