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Add some description about how to failover between wired and wireless

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interface, and how to do it with rc.conf, which is quite useful for
laptop users.

Reported by:	jpaetzel
Sponsored by:	iXsystems, Inc
This commit is contained in:
Xin LI 2010-01-13 08:29:29 +00:00
parent fd00138359
commit 04e0947e28
Notes: svn2git 2020-12-08 03:00:23 +00:00 
svn path=/head/; revision=35179
1 changed files with 98 additions and 0 deletions

98
en_US.ISO8859-1/books/handbook/advanced-networking/chapter.sgml
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@ -2077,6 +2077,25 @@ freebsdap 00:11:95:c3:0d:ac 1 54M 22:1 100 EPS</screen>
</sect3> </sect3>
</sect2> </sect2>
<sect2>
<title>Using both wired and wireless connection</title>
<para>Wired connection provides better performance and reliability,
while wireless connection provides flexibility and mobility,
users of laptop computers usually want to combine these together
and roam seamlessly between the two.</para>
<para>On &os;, it is possible to combine two or even more network
interfaces together in a <quote>failover</quote> fashion, that
is, to use the most preferred and available connection from a
group of network interfaces, and have the operating system to
switch automatically when the link state changes.</para>
<para>We will cover link aggregation and failover in <xref linkend="network-aggregation">
where an example for using both wired and wireless connection
is also provided at <xref linkend="networking-lagg-wired-and-wireless">.</para>
</sect2>
<sect2> <sect2>
<title>Troubleshooting</title> <title>Troubleshooting</title>
@ -3401,6 +3420,85 @@ lagg0: flags=8843&lt;UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST&gt; metric 0 mtu 150
become the active link. If the link is restored on the master become the active link. If the link is restored on the master
interface then it will once again become the active link.</para> interface then it will once again become the active link.</para>
</example> </example>
<example id="networking-lagg-wired-and-wireless">
<title>Failover mode between wired and wireless interfaces</title>
<para>For laptop users, it is usually desirable to make wireless as a
secondary interface, which is to be used when the wired connection
is not available. With &man.lagg.4;, it is possible to use one
IP address, prefer the wired connection for both performance and
security reasons, while maintaining the ability to transfer data
over the wireless connection.</para>
<para>In this setup, we will need to override the underlying
wireless interface's <acronym>MAC</acronym> address to match the &man.lagg.4;'s,
which is inherited from the master interface being used, the
wired interface.</para>
<para>In this setup, we will treat the wired interface,
<replaceable>bge0</replaceable>, as the master, and the wireless
interface,
<replaceable>wlan0</replaceable>, as the failover interface. The
<replaceable>wlan0</replaceable> was created from
<replaceable>iwn0</replaceable> which we will set up with
the wired connection's <acronym>MAC</acronym> address. The first step would be
to obtain the <acronym>MAC</acronym> address from the wired interface:</para>
<screen>&prompt.root; <userinput>ifconfig <replaceable>bge0</replaceable></userinput>
bge0: flags=8843&lt;UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST&gt; metric 0 mtu 1500
options=19b&lt;RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4&gt;
ether 00:21:70:da:ae:37
inet6 fe80::221:70ff:feda:ae37%bge0 prefixlen 64 scopeid 0x2
nd6 options=29&lt;PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL&gt;
media: Ethernet autoselect (1000baseT &lt;full-duplex&gt;)
status: active</screen>
<para>You can replace the <replaceable>bge0</replaceable> to match
your reality, and will get a different <literal>ether</literal>
line which is the <acronym>MAC</acronym> address of your wired interface. Now,
we change the underlying wireless interface,
<replaceable>iwn0</replaceable>:</para>
<screen>&prompt.root; <userinput>ifconfig <replaceable>iwn0</replaceable> ether <replaceable>00:21:70:da:ae:37</replaceable></userinput></screen>
<para>Bring up the wireless interface but don't set up any IP
address on it:</para>
<screen>&prompt.root; <userinput>ifconfig create <replaceable>wlan0</replaceable> wlandev <replaceable>iwn0</replaceable> ssid <replaceable>my_router</replaceable> up</userinput></screen>
<para>Create the &man.lagg.4; interface with <replaceable>bge0</replaceable>
as master, and failover to <replaceable>wlan0</replaceable> if
necessary:</para>
<screen>&prompt.root; <userinput>ifconfig <replaceable>lagg0</replaceable> create</userinput>
&prompt.root; <userinput>ifconfig <replaceable>lagg0</replaceable> up laggproto failover laggport <replaceable>bge0</replaceable> laggport <replaceable>wlan0</replaceable></userinput></screen>
<para>The interface will look something like this, the major
differences will be the <acronym>MAC</acronym> address and the
device names:</para>
<screen>&prompt.root; <userinput>ifconfig <replaceable>lagg0</replaceable></userinput>
lagg0: flags=8843&lt;UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST&gt; metric 0 mtu 1500
options=8&lt;VLAN_MTU&gt;
ether 00:21:70:da:ae:37
media: Ethernet autoselect
status: active
laggproto failover
laggport: wlan0 flags=0&lt;&gt;
laggport: bge0 flags=5&lt;MASTER,ACTIVE&gt;</screen>
<para>To avoid having to do this after every reboot, one can add
something like the following lines to the
<filename>/etc/rc.conf</filename> file:</para>
<programlisting>ifconfig_bge0="up"
ifconfig_iwn0="ether 00:21:70:da:ae:37"
wlans_iwn0="wlan0"
ifconfig_wlan0="WPA"
cloned_interfaces="lagg0"
ifconfig_lagg0="laggproto failover laggport bge0 laggport wlan0 DHCP"
</programlisting>
</example>
</sect2> </sect2>
</sect1> </sect1>