slip.html

FreeBSD操作系统的详细使用手册

<p>Otherwise, if you will use the ``proxy ARP'' method, you will need to assign your SLIP
client's IP addresses out of your SLIP server's Ethernet subnet, and you will also need
to adjust your <tt class="FILENAME">/etc/sliphome/slip.login</tt> and <tt
class="FILENAME">/etc/sliphome/slip.logout</tt> scripts to use <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=arp&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">arp</span>(8)</span></a> to manage the
proxy-ARP entries in the SLIP server's ARP table.</p>
</div>

<div class="SECT4">
<h4 class="SECT4"><a id="AEN31620" name="AEN31620">21.7.2.4.2 <tt
class="FILENAME">slip.login</tt> Configuration</a></h4>

<p>The typical <tt class="FILENAME">/etc/sliphome/slip.login</tt> file looks like
this:</p>

<pre class="PROGRAMLISTING">
#!/bin/sh -
#
#       @(#)slip.login  5.1 (Berkeley) 7/1/90

#
# generic login file for a slip line.  sliplogin invokes this with
# the parameters:
#      1        2         3        4          5         6     7-n
#   slipunit ttyspeed loginname local-addr remote-addr mask opt-args
#
/sbin/ifconfig sl$1 inet $4 $5 netmask $6
</pre>

<p>This <tt class="FILENAME">slip.login</tt> file merely runs <tt
class="COMMAND">ifconfig</tt> for the appropriate SLIP interface with the local and
remote addresses and network mask of the SLIP interface.</p>

<p>If you have decided to use the ``proxy ARP'' method (instead of using a separate
subnet for your SLIP clients), your <tt class="FILENAME">/etc/sliphome/slip.login</tt>
file will need to look something like this:</p>

<pre class="PROGRAMLISTING">
#!/bin/sh -
#
#       @(#)slip.login  5.1 (Berkeley) 7/1/90

#
# generic login file for a slip line.  sliplogin invokes this with
# the parameters:
#      1        2         3        4          5         6     7-n
#   slipunit ttyspeed loginname local-addr remote-addr mask opt-args
#
/sbin/ifconfig sl$1 inet $4 $5 netmask $6 
# Answer ARP requests for the SLIP client with our Ethernet addr
/usr/sbin/arp -s $5 00:11:22:33:44:55 pub
</pre>

<p>The additional line in this <tt class="FILENAME">slip.login</tt>, <tt
class="COMMAND">arp -s $5 00:11:22:33:44:55 pub</tt>, creates an ARP entry in the SLIP
server's ARP table. This ARP entry causes the SLIP server to respond with the SLIP
server's Ethernet MAC address whenever another IP node on the Ethernet asks to speak to
the SLIP client's IP address.</p>

<p>When using the example above, be sure to replace the Ethernet MAC address (<tt
class="HOSTID">00:11:22:33:44:55</tt>) with the MAC address of your system's Ethernet
card, or your ``proxy ARP'' will definitely not work! You can discover your SLIP server's
Ethernet MAC address by looking at the results of running <tt class="COMMAND">netstat
-i</tt>; the second line of the output should look something like:</p>

<pre class="SCREEN">
ed0   1500  &lt;Link&gt;0.2.c1.28.5f.4a         191923 0   129457     0   116
</pre>

<p>This indicates that this particular system's Ethernet MAC address is <tt
class="HOSTID">00:02:c1:28:5f:4a</tt> -- the periods in the Ethernet MAC address given by
<tt class="COMMAND">netstat -i</tt> must be changed to colons and leading zeros should be
added to each single-digit hexadecimal number to convert the address into the form that
<a href="http://www.FreeBSD.org/cgi/man.cgi?query=arp&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">arp</span>(8)</span></a> desires; see
the manual page on <a href="http://www.FreeBSD.org/cgi/man.cgi?query=arp&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">arp</span>(8)</span></a> for complete
information on usage.</p>

<div class="NOTE">
<blockquote class="NOTE">
<p><b>Note:</b> When you create <tt class="FILENAME">/etc/sliphome/slip.login</tt> and
<tt class="FILENAME">/etc/sliphome/slip.logout</tt>, the ``execute'' bit (<tt
class="COMMAND">chmod 755 /etc/sliphome/slip.login /etc/sliphome/slip.logout</tt>) must
be set, or <tt class="COMMAND">sliplogin</tt> will be unable to execute it.</p>
</blockquote>
</div>
</div>

<div class="SECT4">
<h4 class="SECT4"><a id="AEN31660" name="AEN31660">21.7.2.4.3 <tt
class="FILENAME">slip.logout</tt> Configuration</a></h4>

<p><tt class="FILENAME">/etc/sliphome/slip.logout</tt> is not strictly needed (unless you
are implementing ``proxy ARP''), but if you decide to create it, this is an example of a
basic <tt class="FILENAME">slip.logout</tt> script:</p>

<pre class="PROGRAMLISTING">
#!/bin/sh -
#
#       slip.logout

#
# logout file for a slip line.  sliplogin invokes this with
# the parameters:
#      1        2         3        4          5         6     7-n
#   slipunit ttyspeed loginname local-addr remote-addr mask opt-args
#
/sbin/ifconfig sl$1 down
</pre>

<p>If you are using ``proxy ARP'', you will want to have <tt
class="FILENAME">/etc/sliphome/slip.logout</tt> remove the ARP entry for the SLIP
client:</p>

<pre class="PROGRAMLISTING">
#!/bin/sh -
#
#       @(#)slip.logout

#
# logout file for a slip line.  sliplogin invokes this with
# the parameters:
#      1        2         3        4          5         6     7-n
#   slipunit ttyspeed loginname local-addr remote-addr mask opt-args
#
/sbin/ifconfig sl$1 down
# Quit answering ARP requests for the SLIP client
/usr/sbin/arp -d $5
</pre>

<p>The <tt class="COMMAND">arp -d $5</tt> removes the ARP entry that the ``proxy ARP''
<tt class="FILENAME">slip.login</tt> added when the SLIP client logged in.</p>

<p>It bears repeating: make sure <tt class="FILENAME">/etc/sliphome/slip.logout</tt> has
the execute bit set after you create it (ie, <tt class="COMMAND">chmod 755
/etc/sliphome/slip.logout</tt>).</p>
</div>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="AEN31679" name="AEN31679">21.7.2.5 Routing
Considerations</a></h3>

<p>If you are not using the ``proxy ARP'' method for routing packets between your SLIP
clients and the rest of your network (and perhaps the Internet), you will probably have
to add static routes to your closest default router(s) to route your SLIP client subnet
via your SLIP server.</p>

<div class="SECT4">
<h4 class="SECT4"><a id="AEN31686" name="AEN31686">21.7.2.5.1 Static Routes</a></h4>

<p>Adding static routes to your nearest default routers can be troublesome (or impossible
if you do not have authority to do so...). If you have a multiple-router network in your
organization, some routers, such as those made by Cisco and Proteon, may not only need to
be configured with the static route to the SLIP subnet, but also need to be told which
static routes to tell other routers about, so some expertise and troubleshooting/tweaking
may be necessary to get static-route-based routing to work.</p>
</div>

<div class="SECT4">
<h4 class="SECT4"><a id="AEN31691" name="AEN31691">21.7.2.5.2 Running <b
class="APPLICATION"><span class="TRADEMARK">GateD</span>&reg;</b></a></h4>

<div class="NOTE">
<blockquote class="NOTE">
<p><b>Note:</b> <b class="APPLICATION"><span class="TRADEMARK">GateD</span>&reg;</b> is
proprietary software now and will not be available as source code to the public anymore
(more info on the <a href="http://www.gated.org/" target="_top"><span
class="TRADEMARK">GateD</span></a> website). This section only exists to ensure backwards
compatibility for those that are still using an older version.</p>
</blockquote>
</div>

<p>An alternative to the headaches of static routes is to install <b
class="APPLICATION"><span class="TRADEMARK">GateD</span></b> on your FreeBSD SLIP server
and configure it to use the appropriate routing protocols (RIP/OSPF/BGP/EGP) to tell
other routers about your SLIP subnet. You'll need to write a <tt
class="FILENAME">/etc/gated.conf</tt> file to configure your gated; here is a sample,
similar to what the author used on a FreeBSD SLIP server:</p>

<pre class="PROGRAMLISTING">
#
# gated configuration file for dc.dsu.edu; for gated version 3.5alpha5
# Only broadcast RIP information for xxx.xxx.yy out the ed Ethernet interface
#
#
# tracing options
#
traceoptions "/var/tmp/gated.output" replace size 100k files 2 general ;

rip yes {
  interface sl noripout noripin ;
  interface ed ripin ripout version 1 ;
  traceoptions route ;
} ;

#
# Turn on a bunch of tracing info for the interface to the kernel:
kernel {
  traceoptions remnants request routes info interface ;
} ;

#
# Propagate the route to xxx.xxx.yy out the Ethernet interface via RIP
#

export proto rip interface ed {
  proto direct {
      <var
class="REPLACEABLE">xxx.xxx.yy</var> mask 255.255.252.0 metric 1; # SLIP connections
  } ;
} ;

#
# Accept routes from RIP via ed Ethernet interfaces
          
import proto rip interface ed {
  all ;
} ;
</pre>

<p>The above sample <tt class="FILENAME">gated.conf</tt> file broadcasts routing
information regarding the SLIP subnet <var class="REPLACEABLE">xxx.xxx.yy</var> via RIP
onto the Ethernet; if you are using a different Ethernet driver than the <tt
class="DEVICENAME">ed</tt> driver, you will need to change the references to the <tt
class="DEVICENAME">ed</tt> interface appropriately. This sample file also sets up tracing
to <tt class="FILENAME">/var/tmp/gated.output</tt> for debugging <b
class="APPLICATION"><span class="TRADEMARK">GateD</span></b>'s activity; you can
certainly turn off the tracing options if <b class="APPLICATION"><span
class="TRADEMARK">GateD</span></b> works OK for you. You will need to change the <var
class="REPLACEABLE">xxx.xxx.yy</var>'s into the network address of your own SLIP subnet
(be sure to change the net mask in the <var class="LITERAL">proto direct</var> clause as
well).</p>

<p>Once you have installed and configured <b class="APPLICATION"><span
class="TRADEMARK">GateD</span></b> on your system, you will need to tell the FreeBSD
startup scripts to run <b class="APPLICATION"><span class="TRADEMARK">GateD</span></b> in
place of <b class="APPLICATION">routed</b>. The easiest way to accomplish this is to set
the <var class="VARNAME">router</var> and <var class="VARNAME">router_flags</var>
variables in <tt class="FILENAME">/etc/rc.conf</tt>. Please see the manual page for <b
class="APPLICATION"><span class="TRADEMARK">GateD</span></b> for information on
command-line parameters.</p>
</div>
</div>
</div>
</div>

<div class="NAVFOOTER">
<hr align="LEFT" width="100%" />
<table summary="Footer navigation table" width="100%" border="0" cellpadding="0"
cellspacing="0">
<tr>
<td width="33%" align="left" valign="top"><a href="pppoa.html"
accesskey="P">Prev</a></td>
<td width="34%" align="center" valign="top"><a href="index.html"
accesskey="H">Home</a></td>
<td width="33%" align="right" valign="top"><a href="mail.html"
accesskey="N">Next</a></td>
</tr>

<tr>
<td width="33%" align="left" valign="top">Using <b class="APPLICATION">PPP</b> over ATM
(PPPoA)</td>
<td width="34%" align="center" valign="top"><a href="ppp-and-slip.html"
accesskey="U">Up</a></td>
<td width="33%" align="right" valign="top">Electronic Mail</td>
</tr>
</table>
</div>

<p align="center"><small>This, and other documents, can be downloaded from <a
href="ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/">ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/</a>.</small></p>

<p align="center"><small>For questions about FreeBSD, read the <a
href="http://www.FreeBSD.org/docs.html">documentation</a> before contacting &#60;<a
href="mailto:[e-mail]">[e-mail]</a>&#62;.<br />
For questions about this documentation, e-mail &#60;<a
href="mailto:[e-mail]">[e-mail]</a>&#62;.</small></p>
</body>
</html>