config-network-setup.html

这是很好的学习嵌入式LINUX的文章

<li>
<p>The physical media selection is on autoselection mode (<var class="LITERAL">media:
Ethernet autoselect (100baseTX &lt;full-duplex&gt;)</var>). We see that <tt
class="DEVICENAME">dc1</tt> was configured to run with <var
class="LITERAL">10baseT/UTP</var> media. For more information on available media types
for a driver, please refer to its manual page.</p>
</li>

<li>
<p>The status of the link (<var class="LITERAL">status</var>) is <var
class="LITERAL">active</var>, i.e. the carrier is detected. For <tt
class="DEVICENAME">dc1</tt>, we see <var class="LITERAL">status: no carrier</var>. This
is normal when an Ethernet cable is not plugged into the card.</p>
</li>
</ol>

<p>If the <a href="http://www.FreeBSD.org/cgi/man.cgi?query=ifconfig&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">ifconfig</span>(8)</span></a> output had
shown something similar to:</p>

<pre class="SCREEN">
dc0: flags=8843&lt;BROADCAST,SIMPLEX,MULTICAST&gt; mtu 1500
            ether 00:a0:cc:da:da:da
</pre>

<p>it would indicate the card has not been configured.</p>

<p>To configure your card, you need <tt class="USERNAME">root</tt> privileges. The
network card configuration can be done from the command line with <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=ifconfig&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">ifconfig</span>(8)</span></a> but you
would have to do it after each reboot of the system. The file <tt
class="FILENAME">/etc/rc.conf</tt> is where to add the network card's configuration.</p>

<p>Open <tt class="FILENAME">/etc/rc.conf</tt> in your favorite editor. You need to add a
line for each network card present on the system, for example in our case, we added these
lines:</p>

<pre class="PROGRAMLISTING">
ifconfig_dc0="inet 192.168.1.3 netmask 255.255.255.0"
ifconfig_dc1="inet 10.0.0.1 netmask 255.255.255.0 media 10baseT/UTP"
</pre>

<p>You have to replace <tt class="DEVICENAME">dc0</tt>, <tt class="DEVICENAME">dc1</tt>,
and so on, with the correct device for your cards, and the addresses with the proper
ones. You should read the card driver and <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=ifconfig&sektion=8"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">ifconfig</span>(8)</span></a> manual
pages for more details about the allowed options and also <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=rc.conf&sektion=5"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">rc.conf</span>(5)</span></a> manual page
for more information on the syntax of <tt class="FILENAME">/etc/rc.conf</tt>.</p>

<p>If you configured the network during installation, some lines about the network
card(s) may be already present. Double check <tt class="FILENAME">/etc/rc.conf</tt>
before adding any lines.</p>

<p>You will also have to edit the file <tt class="FILENAME">/etc/hosts</tt> to add the
names and the IP addresses of various machines of the LAN, if they are not already there.
For more information please refer to <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=hosts&sektion=5"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">hosts</span>(5)</span></a> and to <tt
class="FILENAME">/usr/share/examples/etc/hosts</tt>.</p>
</div>

<div class="SECT2">
<h2 class="SECT2"><a id="AEN16216" name="AEN16216">11.8.3 Testing and
Troubleshooting</a></h2>

<p>Once you have made the necessary changes in <tt class="FILENAME">/etc/rc.conf</tt>,
you should reboot your system. This will allow the change(s) to the interface(s) to be
applied, and verify that the system restarts without any configuration errors.</p>

<p>Once the system has been rebooted, you should test the network interfaces.</p>

<div class="SECT3">
<h3 class="SECT3"><a id="AEN16221" name="AEN16221">11.8.3.1 Testing the Ethernet
Card</a></h3>

<p>To verify that an Ethernet card is configured correctly, you have to try two things.
First, ping the interface itself, and then ping another machine on the LAN.</p>

<p>First test the local interface:</p>

<pre class="SCREEN">
<samp class="PROMPT">%</samp> <kbd class="USERINPUT">ping -c5 192.168.1.3</kbd>
PING 192.168.1.3 (192.168.1.3): 56 data bytes
64 bytes from 192.168.1.3: icmp_seq=0 ttl=64 time=0.082 ms
64 bytes from 192.168.1.3: icmp_seq=1 ttl=64 time=0.074 ms
64 bytes from 192.168.1.3: icmp_seq=2 ttl=64 time=0.076 ms
64 bytes from 192.168.1.3: icmp_seq=3 ttl=64 time=0.108 ms
64 bytes from 192.168.1.3: icmp_seq=4 ttl=64 time=0.076 ms

--- 192.168.1.3 ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.074/0.083/0.108/0.013 ms
</pre>

<p>Now we have to ping another machine on the LAN:</p>

<pre class="SCREEN">
<samp class="PROMPT">%</samp> <kbd class="USERINPUT">ping -c5 192.168.1.2</kbd>
PING 192.168.1.2 (192.168.1.2): 56 data bytes
64 bytes from 192.168.1.2: icmp_seq=0 ttl=64 time=0.726 ms
64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=0.766 ms
64 bytes from 192.168.1.2: icmp_seq=2 ttl=64 time=0.700 ms
64 bytes from 192.168.1.2: icmp_seq=3 ttl=64 time=0.747 ms
64 bytes from 192.168.1.2: icmp_seq=4 ttl=64 time=0.704 ms

--- 192.168.1.2 ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.700/0.729/0.766/0.025 ms
</pre>

<p>You could also use the machine name instead of <tt class="HOSTID">192.168.1.2</tt> if
you have set up the <tt class="FILENAME">/etc/hosts</tt> file.</p>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="AEN16238" name="AEN16238">11.8.3.2 Troubleshooting</a></h3>

<p>Troubleshooting hardware and software configurations is always a pain, and a pain
which can be alleviated by checking the simple things first. Is your network cable
plugged in? Have you properly configured the network services? Did you configure the
firewall correctly? Is the card you are using supported by FreeBSD? Always check the
hardware notes before sending off a bug report. Update your version of FreeBSD to the
latest STABLE version. Check the mailing list archives, or perhaps search the
Internet.</p>

<p>If the card works, yet performance is poor, it would be worthwhile to read over the <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=tuning&sektion=7"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">tuning</span>(7)</span></a> manual page.
You can also check the network configuration as incorrect network settings can cause slow
connections.</p>

<p>Some users experience one or two ``<tt class="ERRORNAME">device timeout</tt>''
messages, which is normal for some cards. If they continue, or are bothersome, you may
wish to be sure the device is not conflicting with another device. Double check the cable
connections. Perhaps you may just need to get another card.</p>

<p>At times, users see a few ``<tt class="ERRORNAME">watchdog timeout</tt>'' errors. The
first thing to do here is to check your network cable. Many cards require a PCI slot
which supports Bus Mastering. On some old motherboards, only one PCI slot allows it
(usually slot 0). Check the network card and the motherboard documentation to determine
if that may be the problem.</p>

<p>``<tt class="ERRORNAME">No route to host</tt>'' messages occur if the system is unable
to route a packet to the destination host. This can happen if no default route is
specified, or if a cable is unplugged. Check the output of <tt class="COMMAND">netstat
-rn</tt> and make sure there is a valid route to the host you are trying to reach. If
there is not, read on to <a href="advanced-networking.html">Chapter 24</a>.</p>

<p>``<tt class="ERRORNAME">ping: sendto: Permission denied</tt>'' error messages are
often caused by a misconfigured firewall. If <tt class="COMMAND">ipfw</tt> is enabled in
the kernel but no rules have been defined, then the default policy is to deny all
traffic, even ping requests! Read on to <a href="firewalls.html">Section 14.9</a> for
more information.</p>

<p>Sometimes performance of the card is poor, or below average. In these cases it is best
to set the media selection mode from <var class="LITERAL">autoselect</var> to the correct
media selection. While this usually works for most hardware, it may not resolve this
issue for everyone. Again, check all the network settings, and read over the <a
href="http://www.FreeBSD.org/cgi/man.cgi?query=tuning&sektion=7"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">tuning</span>(7)</span></a> manual
page.</p>
</div>
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