linux-ppp.html

Linus guide, Linus guide, Linus guide,

where you should then type <B><TT>pppd</TT></B>. Typing <B>pppd</B> is
<B>critical</B> to establishing the connection.</P>

<A NAME="routing"></A>
<H4><A NAME="7">Possible Routing Problems</A></H4>

<P>If your ISP uses a gateway (a computer that connects you to the rest of
the Internet) that's a different machine than the one you connect to for
dialing in, here's what you should do. You need to change the routing
configuration on your machine so that you can actually be recognized as a
machine on the Internet. The way to tell if you need to change the routing
is if you type <TT>ifconfig</TT> as root, and it shows that you have an IP
address through your modem, but it still doesn't work. The output of
<TT>ifconfig</TT> looks something like this:</P>

<PRE>
eth0      Link encap:Ethernet  HWaddr 00:40:05:48:2E:83
          inet addr:192.168.0.1  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2907 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3343 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          Interrupt:10 Base address:0x300

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:3924  Metric:1
          RX packets:4364 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4364 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0

ppp0      Link encap:Point-to-Point Protocol
          inet addr:207.142.2.34  P-t-P:206.53.129.11  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:576  Metric:1
          RX packets:97 errors:0 dropped:0 overruns:0 frame:0
          TX packets:88 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:10
</PRE>

<P>If it shows the <TT>ppp0</TT> interface, but you can't get
<TT>ping</TT> responses from any hosts, then there might be something
wrong with your routing. The way to fix it? First, type <TT>route</TT> and
it will display something like this:</P>

<PRE>
Kernel IP routing table
Destination     Gateway   Genmask      Flags Metric Ref    Use Iface
127.0.0.0       *         255.0.0.0    U     0      0        3 lo
205.226.158.252 *         0.0.0.0      U     0      0        7 ppp0
</PRE>

<P>As you might expect, most of the IP addresses will probably be
different on your setup. The bottom route is incorrect on my system, so to
change it, I type <TT><B>route del 205.226.158.252 ppp0</B></TT> to delete
it. Then I type <TT><B>route add default ppp0</B></TT> to set the new
route. Or, if you don't want to delete the old route, you can just set the
new route, and it will work just as well. Not deleting the old route is
probably safer.</P>

<P>Those are the only things I had to do. For some reason unknown to me,
that pointed the gateway to the correct address and I successfully
received <TT><B>ping</B></TT> responses.</P>

<A NAME="otherhelp"></A>
<H4><A NAME="8">Other Sources of Help</A></H4>

<P>That should get your dialup connection up and running. If not, keep
trying, or ask for help through any of the *linux* newsgroups or the
#Linux* channels on IRC. (I'd recommend <A
HREF="http://linuxhelp.kennesaw.edu/">#LinuxHelp on the Undernet</A>.)</P>

<P>As usual, I support my work fully, so e-mail me at <A
HREF="mailto:[e-mail]">[e-mail]</A>. Please keep it
short and simple, while providing the necessary information.</P>

<A NAME="chatscript"></A>
<H3><A NAME="9">Using a Chatscript</A></H3>

<P>This is a very convenient way to connect to the Internet. Once you get
this set up, you can connect with a single command. However, there
are things you should know first. Here are things to write down:</P>

<UL>
<LI>What does your login prompt look like? For some ISPs it's <B>login:</B>; for others, it's <B>username:</B>. If you use PAP or CHAP, there will be none.</LI>
<LI>What does your password prompt look like? Usually it's <B>password:</B> but fill whatever your ISP prompts you for if you want this to work. PAP and CHAP users don't get a password prompt.</LI>
<LI>How many lines are in between, say, CONNECT 38400 and the first prompt? This is how many <B>\n</B>'s you will use.</LI>
<LI>Are there any other prompts that are presented to you when you first log in?</LI>
</UL>

<P>The best thing to have done before this is to have made sure that you
could dial in with minicom and use pppd to establish a connection. That
would have ensured that it was possible for you to get connected. This
method is a permanent solution so you won't have to go through the tedious
process of typing several keystrokes and waiting to enter the next
command.</P>

<P>Now, go on to making the actual script. As root, create a file to use
as the actual chatscript (the text file tells the <TT>chat</TT> program
how to communicate with your modem). I suggest giving it a name with the
.chat file extension; for the sake of simplicity, let's just say that
we'll use <TT>yourispname.chat</TT> as the filename. To edit the file,
type <TT><B>pico yourispname.chat</B></TT>.</P>

<P>Now put in the following lines into yourispname.chat:</P>

<PRE>
""AT&amp;D2
OK ATDT#phone#
38400 \n
ogin: foobar
word: altm.415
</PRE>

<P>In place of AT&amp;D2 you can plug in the initialization string that
you use. In place of #phone# you should put in the number that you want
your modem to call, so for me it would look like <TT>ATDT4755868</TT>. The
'38400' represents the speed you want to connect at and '\n' is telling
<TT>chat</TT> to expect a new line. The part saying 'ogin: foobar' is
telling <TT>chat</TT> to expect the text 'ogin:' to appear somewhere and
respond to it by sending the word 'foobar'. The same applies to the next
line. Don't put in the last two lines if you're using PAP or CHAP because
the passwords aren't authenticated with plain text like that.</P>

<P>Basically you type in any prompts that are presented to you, and then
type in what to send back. What is presented and what is sent back can be
separated by a space in between.</P>

<P>If you dial in, watch for the number of lines between your baud rate
(like 38400) and the <B>login:</B> prompt; if there's one line in between,
use one \n character; if there are two, use two \n characters, and so on.
Be sure to watch out for this.</P>

<P>To prevent users other than root from reading from the file and finding
out your password for logging in to your provider, you should change the
permissions on the chatscript so that only root can read from it. I would
do this by typing <B><TT>chmod go-rwx yourispname.chat</TT></B>.</P>

<P>Now, you should make another script -- a normal (shell) script. Move to
<TT>/usr/sbin</TT> as root and create the script. Let's call it
<TT>yourispname</TT>. Now we proceed to edit the file by typing <TT>pico
yourispname</TT> in <TT>/usr/sbin</TT>. Keep in mind that you can change
the filenames to whatever you want.</P>

<P>Put the following lines into the normal (shell) script,
yourispname:</P>

<PRE>
pppd connect 'chat -f /root/yourispname.chat' /dev/modem 38400 \
0.0.0.0: asyncmap 0 crtscts defaultroute
</PRE>

<P>You might want to change the path to <TT>yourispname.chat</TT>, having
it correspond to the directory that you placed <TT>yourispname.chat</TT>. 
After you put in this line, make the file executable and only to be
accessed by root (the head honcho on the system) by typing <TT>chmod 700
yourispname.chat</TT>.</P>

<P>To connect, all you have to do is type the name of the file that you
created. All this should be done as root.</P>

<A NAME="disconnect"></A>
<H3><A NAME="10">Disconnecting</A></H3>

<P>The way I disconnect is I type <TT>killall pppd</TT>, which kills the
pppd program from running and therefore shuts down communication between
your modem and your ISP.</P>

<P><A HREF="mailto:[e-mail]">Jas</A> has suggested this
shellscript:</P>

<PRE>
#!/bin/sh
kill -TERM `cat /var/run/ppp0.pid`
</PRE>

<P>That means you'd put that in a file using a text editor such as
<B>pico</B> or <B>vim</B>, and save it as whatever filename you want
(<B>ppp-down.sh</B> for Jas' example). Then when you're back at the
prompt, type <B><TT>chmod +x ppp-down.sh</TT></B> so that it can be run
(executed). I guess I should try this when I disconnect...</P>

<A NAME="modemtrouble"></A>
<H3><A NAME="11">Modem Trouble</A></H3>

<P>There might be all sorts of problems you encounter that are related to
your modem, and that is a major obstacle for a lot of people.</P>

<A NAME="winmodem"></A>
<H4><A NAME="12">PnP and Winmodem</A></H4>

<P>Linux users who have plug n' play (PnP) modems or the notorius WinModem
from US Robotics might have a lot of trouble in getting Linux to recognize
that their modem is present. The best solution is to use another modem,
make sure that it doesn't say &quot;WinModem&quot;, &quot;Plug n'
Play&quot;, &quot;PnP&quot;, &quot;Exclusively for Windows&quot;, or
anything similar.</P>

<P>Two ways you can try to get Linux to recognize PnP devices are messing
with your BIOS (set the &quot;PnP OS Installed&quot; option to
&quot;off&quot;) and/or loading Windows 95 first, then using a DOS program
called Loadlin to boot a copy of your Linux kernel, usually found as the
file called <B><TT>vmlinuz</TT></B> in your <TT>/boot/</TT> directory. The
file, <B>LOADLIN.EXE</B>, is usually available from your Linux
distribution media, be it FTP or CD-ROM.</P>

<A NAME="irqconflict"></A>
<H4><A NAME="13">IRQ Conflict</A></H4>

<P>Your modem might try to be sharing the same means of communicating with
the system with another device that has the same interrupt request, or
IRQ. Symptoms of this include an abnormally slow connection, an error
about timeouts sending config-requests, and a disconnect soon
afterwards.</P>

<P>HydroFlow from <A HREF="http://linuxhelp.kennesaw.edu/"
TARGET="_top">IRC on the Undernet</A> told me that all he had to do was
type <B><TT>setserial /dev/modem irq 10</TT></B> to get it working. Of
course, that's his system, so change the IRQ to fit your own system
settings. Then the instructions seemed to have worked.</P>

<P>You can check for what devices have which IRQ settings by typing <B>cat
/proc/interrupts</B>.</P>

<A NAME="initstrings"></A>
<H4><A NAME="14">Finding Exact Init Strings</A></H4>

<P>Since some of you might be wondering about how to find exact
initialization strings for your modem, <A
HREF="mailto:[e-mail]">FusionGyro</A> wrote:</P>

<P><I>I would like to offer a tip for you to possibly include in your FAQ
file.  For people coming to Linux from Windows 9x, there is a
&quot;simple&quot; way to find all of the exact complicated modem strings.  
First, make sure you have logged on to your ISP since you booted.  Then
just fire up the control panel, open &quot;Modems&quot;, highlight the
correct modem, press &quot;Properties&quot;, hit the
&quot;Connection&quot; tab, press &quot;Advanced&quot;, and then hit
&quot;View Log&quot;.  (Gee, that wasn't so easy, was it ;).  You should
be staring at a text file.  This file will contain everything that was
sent and recieved until a PPP connection was made.</I> Here's a cutout from the
example he gave:</P>

<PRE>
12-13-1998 02:56:07.36 - Cirrus Logic 33600 bps PnP V34 in use.
12-13-1998 02:56:07.36 - Modem type: Cirrus Logic 33600 bps PnP V34
12-13-1998 02:56:07.36 - Modem inf path: MDMTI.INF
12-13-1998 02:56:07.36 - Modem inf section: Modem4
12-13-1998 02:56:07.61 - 115200,N,8,1
12-13-1998 02:56:07.62 - 115200,N,8,1
12-13-1998 02:56:07.62 - Initializing modem.
12-13-1998 02:56:07.75 - Recv: &lt;cr&gt;
12-13-1998 02:56:08.22 - Interpreted response: Ok
12-13-1998 02:56:08.22 - Send: ATS7=60\T0L1M1\N3-J1%C1&quot;H3\Q3B0N1X4&lt;cr&gt;
12-13-1998 02:56:27.67 - Recv: COMPRESSION:V42B
12-13-1998 02:56:27.67 - Interpreted response: Informative
12-13-1998 02:56:27.67 - Recv: &lt;cr&gt;
12-13-1998 02:56:27.67 - Interpreted response: Informative
12-13-1998 02:56:27.67 - Recv: &lt;lf&gt;
12-13-1998 02:56:27.67 - Error-control on.
12-13-1998 02:56:27.67 - Data compression on.
</PRE>

<P><I>While much of it is useless, it does contain the important stuff: AT
&amp;F E0 V1 W4 &amp;D2 &amp;C1 S0=0 -C1, etc.</I></P>

<!-- This paragraph added on Tue Mar 2 16:26:50 PST 1999 -->

<P><A HREF="mailto:[e-mail]">Poul Petersen</A> wrote in
about a site where you can look up information about your modem,
including the init string. It's at <A
HREF="http://www.spy.net/~dustin/modem/">http://www.spy.net/~dustin/modem/</A>.</P>

<A NAME="notes"></A>
<H3><A NAME="15">Author's Notes</A></H3>

<P>When you're upgrading from, say, a generic 14.4 to a 33.6, and both
are external, the only settings you need to change in minicom (or the
chatscript) are the baud rates and the initialization string. The
standard dial string (ATDT) should work for old modems as well as new
ones.</P>

<A NAME="nopico"></A>
<H4><A NAME="16">No Pico?</A></H4>

<P>If you don't have <B><TT>pico</TT></B> installed, try some other text
editor (<TT>emacs</TT>, <TT>vi</TT>, <TT>joe</TT>, or <TT>jed</TT>) that
you might be able to use to edit that file. Use that instead of
&quot;pico&quot; wherever &quot;pico&quot; appears as a command. It
doesn't matter what text editor you use.</P>

<HR>

<P><B><FONT SIZE="-1">Copyright &copy; 1997-1999 <A
HREF="mailto:[e-mail]">Joshua Go
([e-mail])</A>. All rights reserved. Permission to use,
distribute, and copy this document is hereby granted. You may modify
this document as long as credit to me is given.</FONT></B></P>

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