<sect1 id="connectivity-ppp-server">

    <title>The Server Computer</title>

    <para>

        When you are configuring the server computer, you need to

        install and configure both <application>mgetty</application>

        and <application>pppd</application> programs.  The

        <application>mgetty</application> program lets you attend

        incoming calls and must be configured to run through

        <systemitem class="daemon">init</systemitem> daemon in order

        to take control over the Modem device. By default, inside

        &TC;; (release 5.5), <application>mgetty</application> isn't

        configured to start with 

        class="daemon">init</systemitem> daemon so you need to do it

        yourself (see 

        linkend="connectivity-ppp-server-mgetty-inittab" />).

        Later, for attending connection requests, you need to

        configure <application>mgetty</application> to use the

        <application>pppd</application> program, so the Point-to-Point

        Protocol (PPP) can be talked and IP packages can be exchange

        between the client computer and the server computer. Later,

        you need to configure <application>pppd</application> to

        adjust it to your needs (see 

        linkend="connectivity-ppp-server-pppd-options" />). Once

        you've configured both <application>mgetty</application> and

        <application>pppd</application> programs, the server computer

        should be ready to attend incoming calls.

    </para>

    <sect2 id="connectivity-ppp-server-mgetty">

    <title><package>mgetty</package></title>

    <para>

        Taken from <command>mgetty</command> man page: — Mgetty

        is a <quote>smart</quote> getty replacement, designed to be

        used with hayes compatible data and data/fax modems. Mgetty

        knows about modem initialization, manual modem answering (so

        your modem doesn’t answer if the machine isn’t ready), UUCP

        locking (so you can use the same device for dial-in and

        dial-out).  Mgetty provides very extensive logging facilities

        —.

    </para>

    <para>

        Before using the configuration provided here, it would be

        useful for you to read the documentation provided in the

        <package>mgetty</package> and <package>SysVinit</package>

        packages.  This will let you to understand what you are

        configuring.

    </para>

    <sect3 id="connectivity-ppp-server-mgetty-inittab">

    <title><filename>/etc/inittab</filename></title>

<screen>

# Run mgetty to control a Multi-Tech (MT5634ZBA-USB) modem attached to

# `/dev/ttyAMC0' device. Incoming calls will be attended without fax

# initalization.

ACM0:2345:respawn:/sbin/mgetty -D ttyACM0

</screen>

    </sect3>

    <sect3 id="connectivity-ppp-server-mgetty-login">

    <title><filename>/etc/mgetty+sendfax/login.config</filename></title>

<screen>

# Automatic PPP startup on receipt of LCP configure request (AutoPPP).

# mgetty has to be compiled with "-DAUTO_PPP" for this to work.

# Warning: Case is significant, AUTOPPP or autoppp won't work!

# Consult the "pppd" man page to find pppd options that work for you.

#

#  NOTE: for *some* users, the "-detach" option has been necessary,

#  for others, not at all. If your pppd doesn't die after hangup, try

#  it.

#

#  NOTE2: "debug" creates lots of debugging info.  LOOK AT IT if

#  things do not work out of the box, most likely it's a ppp problem!

#

#  NOTE3: "man pppd" is your friend!

#

#  NOTE4: max. 9 arguments allowed.

#

#/AutoPPP/ -    a_ppp   /usr/sbin/pppd auth -chap +pap login debug

/AutoPPP/ -     a_ppp   /usr/sbin/pppd 192.168.1.1:192.168.1.2

</screen>

    <para>

        In this configuration, we set both local and remote IP

        addresses to fix the IP information used by computers once the

        PPP connection has been established.  All other options are

        taken from the <filename>options</filename> file (see 

        linkend="connectivity-ppp-server-pppd-options" />). If we

        don't specify both local and remote IP addresses when pppd is

        initialized, pppd will try to take such information from the

        first Modem device you configured (e.g., ppp0) and will expect

        the remote peer to provide its IP address. This situation can

        introduce some contraditions (e.g., the local and remote

        address may be on a different network.) that would make the

        connection to fail.

    </para>

    <para>

        Another issue we might face out would be the netmask

        specification of the poin-to-point network established between

        the two computers. Inside the pppd-2.4.4 man page there is no

        reference to the <option>netmask</option> option, however,

        there is a mention to it on the sample files installed with it

        which is quiet confussing. It seems to be required that one of

        the two computers establishing connection defines the netmask

        information of the network they are creating. So, to do it on

        the server computer (the one receiving calls), it is needed to

        set the netmask definition in the Modem device configuration

        file of it (

        />) along with the local IP address. Otherwise, even local and

        remote IP addresses be specified through the pppd, the

        connection will end up having the 255.255.255.255 netmask

        which would let you ping the computer on the other end but

        that will not last too long before it fails and iptables seems

        to get very confused about it.

    </para>

    <para>

        Since we are already using 

        class="daemon">pppd</systemitem> to attend login requests,

        there is no need to invoke the

        <application>login</application> program. So, comment the

        related line as described below.

    </para>

<screen>

#*      -       -       /bin/login @

</screen>

    </sect3>

    <sect3 id="connectivity-ppp-server-mgetty-dialin">

    <title><filename>/etc/mgetty+sendfax/dialin.config</filename></title>

    <para>

        I didn't touch this file, but you might need to.

    </para>

    </sect3>

    <sect3 id="connectivity-ppp-server-mgetty-config">

    <title><filename>/etc/mgetty+sendfax/mgetty.config</filename></title>

    <para>

        I didn't touch this file, but you might need to.

    </para>

    </sect3>

    </sect2>

    <sect2 id="connectivity-ppp-server-pppd">

    <title><package>pppd</package></title>

    <para>

        Taken from pppd man page: — PPP is the protocol used for

        establishing internet links over dial-up modems, DSL

        connections, and many other types of point-to-point links.

        The pppd daemon works together with the kernel PPP driver to

        establish and maintain a PPP link with another system (called

        the peer) and to negotiate Internet Protocol (IP) addresses

        for each end of the link. Pppd can also authenticate the peer

        and/or supply authentication information to the peer.  PPP can

        be used with other network protocols besides IP, but such use

        is becoming increasingly rare —.

    </para>

    <para>

        Before using the configuration provided here, it would be

        useful for you to read the documentation provided in the

        <package>ppp</package> package.  This will let you to

        understand what you are configuring.

    </para>

    <sect3 id="connectivity-ppp-server-pppd-options">

    <title><filename>/etc/pppd/options</filename></title>

<screen>

# Enables connection debugging facilities.  If this option is given,

# pppd will log the contents of all control packets sent or received

# in a readable form.  The packets are logged through syslog with

# facility daemon and level debug.  This information can be directed

# to a file by setting up /etc/syslog.conf appropriately (see

# syslog.conf(5)).

debug

# Require the peer to authenticate itself before allowing network

# packets to be sent or received. This option is the default if the

# system has a default route.  If neither this option nor the noauth

# option is specified, pppd will only allow the peer to use IP

# addresses to which the system does not already have a route.

auth

# Specifies that pppd should create a UUCP-style lock file for the

# serial device to ensure exclusive access to the device.  By default,

# pppd will not create a lock file.

lock

# Specify which DNS Servers the incoming Win95 or WinNT Connection

# should use Two Servers can be remotely configured.

ms-dns 192.168.1.1

# If this option is given, pppd will send an LCP echo-request frame to

# the peer every n seconds. Under Linux, the echo-request is sent when

# no packets have been received from the peer for n seconds. Normally

# the peer should respond to the echo-request by sending an

# echo-reply.  This option can be used with the lcp-echo-failure

# option to detect that the peer is no longer connected.

lcp-echo-interval 30

# If this option is given, pppd will presume the peer to be dead if n

# LCP echo-requests are sent without receiving a valid LCP echo-reply.

# If this happens, pppd will terminate the connection.  Use of this

# option requires a non-zero value for the lcp-echo-interval

# parameter.  This option can be used to enable pppd to terminate

# after the physical connection has been broken (e.g., the modem has

# hung up) in situations where no hardware modem control lines are

# available.

lcp-echo-failure 4

# Specifies that pppd should disconnect if the link is idle for n

# seconds.

idle 60

# Specifies that pppd should disconnect if the link have been active

# for n seconds.

maxconnect 900

# Disable the IPXCP and IPX protocols.

noipx

</screen>

    </sect3>

    <sect3 id="connectivity-ppp-server-pppd-cha">

    <title><filename>/etc/pppd/cha-secrets</filename></title>

<screen>

# Secrets for authentication using CHAP

# client        server  secret                  IP addresses

# Specify the client configuration. This is when this manchine calls

# someone's else machine and tries to establish a point-to-point

# connection. Most of this configuration is handled by the

# `system-config-network' utility.

#

####### redhat-config-network will overwrite this part!!! (begin) ##########

####### redhat-config-network will overwrite this part!!! (end) ############

# Specify the server configuration. This is when someone's else

# machine calls this machine trying to establish a point-to-point

# connection.  This part of the configuration isn't handled by

# `system-config-network' utility. By default, there is one line to

# verify client's identity with authenticating it and one line to let

# the server computer to authenticate itself with the client computer

# in case the client computer requires so. All client computers will

# be authenticated through the `faith' user.  However, it is possible

# to provide anonymous authentication to client computers by using an

# empty client identity (as explained in pppd's man page) in order to

# restrict the IP address they can use.

#

"faith"         "projects"      "mail4u.2k10"   "192.168.1.2"

#""             "projects"      ""              "192.168.1.2"

"projects"      *               "mail4u.2k10"

</screen>

    <para>

        Assuming the hostname of the server computer is

        <quote>projects</quote>, when a client computer uses the faith

        username to login on it, the 

        class="ipaddress">192.168.1.2</systemitem> IP address will be

        assigned to that client computer after a successful

        authentication.  This configuration is just for one Modem

        device attached to the server computer.  In case you have more

        than one Modem device attached to the server computer, it

        would be necessary to add one username for each Modem device

        you have, in order to permit the client computers to connect

        simultaneously. It is not possible to have two or more

        computers with the same IP address in the same network.

    </para>

    </sect3>

    <sect3 id="connectivity-ppp-server-pppd-pap">

    <title><filename>/etc/pppd/pap-secrets</filename></title>

    <para>

        This file contains the same information of

        <filename>cha-secrets</filename> file does. See 

        linkend="connectivity-ppp-server-pppd-cha" />. 

    </para>

    </sect3>

    </sect2>

</sect1>