LDP/LDP/howto/docbook/Cable-Modem.sgml

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<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook V3.1//EN"> <article>
<!-- Header -->
<artheader>
<!-- title of HOWTO, include the word HOWTO -->
<title>The Cable Modem HOWTO</title>
<author><firstname>Howard</firstname><surname>Shane</surname>
<affiliation>
<address><email>hshane[AT]austin.rr.com</email></address>
</affiliation>
</author> <!--revision history--> <revhistory>
<revision>
<revnumber>0.9</revnumber>
<date>2004-07-30</date>
<authorinitials>jhs</authorinitials>
<revremark>Completed draft.</revremark>
</revision>
</revhistory> <!-- additional (*earlier*) revision histories go here, if any -->
<!--abstract-->
<abstract>
<indexterm> <primary>Modem</primary> <secondary>Cable</secondary> </indexterm>
<para> This document was written to assist the Linux user in configuring a cable modem
for internet access using a cable network. </para> </abstract>
</artheader>
<!-- Section1: intro -->
<sect1 id="intro"> <title>Introduction</title>
<indexterm><primary>>disk!introduction</primary></indexterm>
<para> This document was written to assist the Linux user in setting up their cable
modem, and includes information on configuring a DHCP client, enabling the device
with or without USB support and troubleshooting. I have successfully configured
Motorola and Toshiba brand cable modems with the methods herein, and others have
informed me that the configuration methods of other manufacturers' hardware is almost
identical. A mostly-complete laundry list of hardware specific tidbits is addressed
in <xref linkend="hardware">; if you have a model working that is not listing or have
some specific informtion that you think will be helpful, please send it along via the
address in <xref linkend="feedback"> </para>
<!-- Section2: copyright -->
<sect2 id="copyright"> <title>Copyright Information</title> <para> This document
is Copyright 2004 by Howard Shane. </para> <para> Permission is granted to copy,
distribute and/or modify this document under the terms of the GNU Free Documentation
License, Version 1.2 or any later version published by the Free Software Foundation
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of
the license can be found in <xref LinkEnd="appendix">. </para> </sect2>
<sect2 id="disclaimer"> <title>Disclaimer</title> <para> No liability for the
contents of this document can be accepted. Use the concepts, examples and other
content entirely at your own risk. As this is a new edition, there may be technical
or other inaccuracies that may result in the loss of irreplaceable data. In any case,
proceed with caution, and realize that although errors are highly unlikely, the author
can accept no responsibility for them. </para>
<para> All copyrights are held by their by their respective owners, unless specifically
noted otherwise. Use of a term in this document should not be regarded as affecting
the validity of any trademark or service mark. </para>
<para> Naming of particular products or brands should not be seen as endorsements.
</para>
</sect2>
<sect2 id="newversions"> <title>New Versions</title>
<indexterm> <primary>(your index root)!news on</primary> </indexterm>
<para> This is the initial release. </para>
<para> The latest version number of this document can be found <ulink
url="http://www.hshanemd.net/docs/HOWTOS/Cable-Modem/">here</ulink>.</para> </sect2>
<!-- Section2: credits -->
<sect2 id="credits"> <title>Credits</title> <para> I would like to thank Brad Hards, the
primary author of the Linux CDCEther kernel driver for graciously volunteering several
useful bits of information, as well as Rob McGee and Jess Portnoy for encouraging
me to morph this document into the new Cable-Modem HOWTO and contributing useful
suggestions.</para> <para> Also, I would like to thank Marla, who has stood by me
confidently even when the outlook was dimmest and others unforgiving. I'm yours forever.
</para> </sect2>
<sect2 id="feedback"> <title>Feedback</title> <para> Please send any additions
or comments pertaining to this document to the following email address:
<email>hshane[AT]austin.rr.com</email>. </para></sect2> <sect2 id="conventions">
<title>Conventions Used in this Document</title> <para> The following conventions are
used in this document and are outlined here for those who may not yet have a complete
understanding of how to access and control the underlying operating system in Linux,
which is almost always the bash shell.</para> <para> First, filenames are referenced in
a paragraph like so: <filename>/path/file</filename></para> <para> Commands in Linux are
executed (or 'called') at the command prompt, otherwise known as the 'command line.' If
you are in the non-graphical (text-based) environment you will usually be presented
the bash shell prompt which is a dollar sign: <screen>$</screen>...or the hash mark:
<screen>#</screen>...if you have logged in as root or have acquired root, or 'superuser'
privileges. You can also access the bash shell in the X window system, otherwise known
as X or X11, with an <ulink url="http://invisible-island.net/xterm/">xterm</ulink>
or similar X-terminal-emulator. Commands to be performed at the bash prompt, but
referenced in a paragraph of this document, usually look like this: <command>do this
now</command></para> <para> Commands and/or the resulting output of commands may also be
outlined with screen output in their own paragraph or heading:</para> <para> <screen>$
date Sun Jul 27 22:37:11 CDT 2003</screen></para> <para>When a command is written in
front of the bash prompt (e.g. <command>$ date</command> above), it is assumed the
[Return] or [Enter] key has been depressed after the command, possibly followed by
the output (e.g., the date).</para>
</sect2>
</sect1>
<!-- Section1: intro: END --> <!-- Section1 begins-->
<sect1 id="prerequisites"> <title>Prerequisites</title> <sect2 id="networking">
<title>Networking and Ethernet Support</title>
<para>Most, if not all, cable modems are easily configured for use with Linux.
Most cable modems have two possible interfaces for connection to your computer:
Ethernet or USB. If your version of Linux is like most, there is very little you will need to do to get your cable modem
working with an Ethernet interface as long as you have support for networking and the driver for your specific networking hardware installed.
</para>
</sect2>
<sect2 id="nic">
<title>Ethernet Support</title>
<para>
An open Ethernet interface is the most likely means that a cable provider will use or recommend when
setting up your cable internet service. Your ISP may even deliver and/or install a new NIC card to access the modem if you have no open Ethernet cards available.The cable connects to the modem, which then connects to your NIC using ordinary 10BaseT/100BaseT Ethernet cable. If you are uncertain about any of the above, and your modem and/or NIC are not already physically installed for you, read the <ulink url="http://www.tldp.org/HOWTO/Ethernet-HOWTO.html">Ethernet HOWTO</ulink> and your
cable modem's instruction manual before proceeding any further.</para> <warning><para>Do not try to install an NIC by yourself unless you are already familiar with the process or are assisted by someone who is.</para></warning>
<para>
For software support, most base installs of Linux distributions come enabled for TCP/IP networking and common Ethernet
hardware drivers 'out of the box,' so if you are using a preconfigured
kernel from a boxed or downloaded version of a Linux distribution you can probably skip to <xref
linkend="modem">. If you don't know what a kernel is and/or are curious about it, see
the <ulink url="http://www.tldp.org/HOWTO/Kernel-HOWTO.html">Kernel HOWTO</ulink>
for more information.</para>
<para>
The (Linux kernel) networking support requirements for use of a cable modem include the following, and which you will need to select
using whatever kernel configuration front-end application (whether <command>make config</command>, <command>make menuconfig</command> or <command>make
xconfig</command>) prior to compiling a custom kernel. For 2.4.x and earlier kernels under the heading 'Networking options' you will require 'TCP/IP Networking' along with 'Network Device Support,' go to 'Ethernet (10 or 100Mbit) Support' and enable your specific NIC driver. If you use the 2.6.x series, the heading 'Drivers' has a sub-heading 'Networking Support,' where you should enable 'Network Device Support' and 'Ethernet Connection Support/Ethernet (10 or 100Mbit), as well as your specific NIC hardware driver.</para>
<para>If you are interested in how to configure the USB interface go to <xref linkend="usbconfig">; otherwise you can go to <xref linkend="modem">.</para>
</sect2>
<sect2 id="usbconfig"><title>USB Interface Support</title>
<para>
There seems to be no reliable data regarding testing bandwidth or performance of an Ethernet connection vs. the USB port of cable modems. In theory they should be equivalent, though some believe there is poorer performance (at least in Linux) using USB. Unless you have no way to use an Ethernet interface, have no ability to add a cheap NIC, or are just plain determined, there is probably no advantage to using USB. If so, you will need the following, in addition to Networking support outlined above: 1) USB Subsystem support 2) your host controller driver (UHCI, OHCI or EHCI) and one of the following:
</para>
<para>
Kernel Version 2.4.x
</para>
<itemizedlist>
<listitem><para>
CDC Ethernet Support</para></listitem>
</itemizedlist>
<para>
For kernel 2.6.x you will need
</para>
<itemizedlist>
<listitem><para>
Multi-purpose USB Networking Framework (CONFIG_USB_USBNET) with</para></listitem>
<listitem><para>CDC Ethernet support (CONFIG_USB_CDCETHER)</para></listitem>
</itemizedlist>
<para>
See <xref linkend="usb"> for instructions on how to load modules when time to test the modem.</para>
</sect2>
<sect2 id="modem"> <title>The Modem Device</title> <para> First, plug in and turn on
the cable modem. Connect your Ethernet card to the modem with 10BaseT/100BaseT cable
into the non-USB interface if this was not already done for you. Be sure the modem
isn't on standby mode or turned off; this should be obvious looking at the LEDs. The
standby button is on the top of the device on most models. Note that your cable internet
provider should be able to tell remotely whether your modem is connected and functioning
properly, which is helpful to differentiate hardware from configuration problems on
your end. They will also need the MAC (Media Access Control) hardware address of your
modem to allow the device access to their network. If at any time you substitute one
modem for another you will need to inform them so the MAC address can be updated and
your access to the cable network restored. </para> <para> Your modem will be assigned
an IP address once connected for the first time that may remain the same or may change
periodically depending on the IP address turnover of your ISP's DHCP server and how
long you remain offline if you disconnect. </para> </sect2>
<sect2 id="DHCP"> <title>The DHCP Client</title> <sect3 id="DHCP-deb">
<title>Installation on a Debian System</title> <para> Debian requires you have a DHCP
client package installed and running. As of this writing there are two user-space
programs for this. In Woody (stable), there is the dhcp-client package, automatically
installed as a part of the base packages as <filename>/sbin/dhclient</filename>. For
Sarge (testing) and up, this has been replaced by the dhcpcd package. The latter
has its configuration files under <filename>/etc/dhcpc</filename>, but nothing really
needs to be modified if you have only one Ethernet card you will be using for the cable
internet service. The dhcpcd daemon is easily installed for those using testing branch
as root with <command>apt-get install dhcpcd </command>. </para> </sect3>
<sect3 id="DHCP-rpm"> <title>Installing on .rpm- or .tgz-Based Systems</title>
<para> For .rpm- or .tgz-based distributions, I offer the following
link that walks you through the setup of a DHCP client, in the <ulink
url="http://www.tldp.org/HOWTO/mini/DHCP/x74.html">DHCP mini-HOWTO</ulink>. </para>
<para> Just run <command> /sbin/dhclient </command> or whichever client you use to
get a dynamic IP address. </para> </sect3> </sect2> </sect1>
<sect1 id="configuration"> <title>Configuration</title> <sect2 id="eth">
<title>Ready to Start With an Ethernet-Modem connection</title> <para> Once you
are plugged into the system, your modem is on and your dhcp server is running as
outlined in <xref linkend="dhcp">, you should be provided your own IP address that
doesn't change unless you drop the lease (i.e. are offline) for a while. To confirm
that the DHCP client is working and you have a new IP address, execute (as root)
<command>ifconfig</command> without any other arguments, and you should see the
following: </para> <para> <screen>eth0 Link encap:Ethernet HWaddr 00:D0:09:DE:D4:6F
inet addr:66.190.XXX.XXX Bcast:255.255.255.255 Mask:255.255.255.0 UP BROADCAST
RUNNING MULTICAST MTU:1500 Metric:1 RX packets:2591777 errors:0 dropped:0
overruns:0 frame:0 TX packets:5589 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100 RX bytes:168673636 (160.8 MiB) TX bytes:1752872
(1.6 MiB) Interrupt:12 Base address:0xc400
</screen> </para> <para> <screen>lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0 UP LOOPBACK RUNNING MTU:16436 Metric:1 RX
packets:5168 errors:0 dropped:0 overruns:0 frame:0 TX packets:5168 errors:0
dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:1695104
(1.6 MiB) TX bytes:1695104 (1.6 MiB)
</screen></para> <para> ...which shows the system loopback device,
<emphasis>lo</emphasis>, and also <emphasis>eth0</emphasis>, the cable modem having
successfully acquired an IP address (the 'inet addr') provided by our cable internet
service provider.</para> <para> A simple Ethernet-based configuration should be complete
at this step. If you have more than one Ethernet interface available and want to select
a specific one for the cable service, go on to <xref linkend="device-iface">. </para>
</sect2>
<sect2 id="device-iface"> <title>Grabbing A Specific Interface</title> <para> Let's say
we want to select a specific Ethernet interface (<emphasis>ethX</emphasis>) to be the
recipient of the DHCP cable internet service. If you run <command>ifconfig</command>
as root you get a list of open devices: </para> <para><screen>eth0 Link encap:Ethernet
HWaddr 00:D0:09:DE:D4:6F
inet addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0 BROADCAST RUNNING
MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) Interrupt:12 Base address:0xc400
</screen></para> <para><screen>lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0 UP LOOPBACK RUNNING MTU:16436 Metric:1 RX
packets:5168 errors:0 dropped:0 overruns:0 frame:0 TX packets:5168 errors:0
dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:1695104
(1.6 MiB) TX bytes:1695104 (1.6 MiB)
</screen></para> <para>...where eth0 is a standard NIC that we have preconfigured to
the IP address 192.168.1.1.</para>
<para> Note the HWaddr field, or hardware address, on the first line. This is the same
as the MAC, or Media Access Control address, and is how we will specify the interface
for each action. </para>
<sect3 id="manual"> <title>Manually Assigning MAC to Interface Name</title> <para>
Whatever distribution you use, you can always use the command line to designate an
Ethernet device (via the MAC) to be interface '<emphasis>ethX</emphasis>' with or without
a particular IP address. This may be necessary when you change your settings, swap out
hardware or for just plain testing. Use ifconfig: </para>
<para> <screen># ifconfig ethX hw ether 00:D0:09:DE:D4:6F up
</screen></para> <para>You can check if it worked by calling
<command>ifconfig</command> without options after your next reboot. See <command>man
ifconfig</command> for more options.</para>
</sect3>
<sect3 id="autoconfig"> <title>Automatic Configuration of Devices</title> <para> The
method for automatically assigning a particular interface name <emphasis>ethX</emphasis>,
to a specific hardware interface (Media Access Control address) differs by distribution.
</para>
<sect4 id="deb"> <title>Debian</title> <para> If you are running a Debian system,
you can alter the <filename>/etc/network/interfaces</filename> file to look like
this:</para> <para><screen>
# /etc/network/interfaces -- configuration file for ifup(8), ifdown(8) # The
loopback interface auto lo iface lo inet loopback auto eth0 iface eth0 inet
static address 192.168.1.1 netmask 255.255.255.0 network 192.168.1.0 hwaddress
ether 00:D0:09:DE:D4:6F
auto eth1 iface eth1 inet dhcp hwaddress ether 00:04:BD:DE:42:0B
</screen></para> <para> The <command>auto eth0</command> and <command>auto eth1</command>
are required to have the interfaces configured at boot-up. Note that some versions
of dhcp clients by default always grab eth0 for the dhcpc interface. So even
after doing all the above, unless you specifically run <command>/sbin/dhcpcd-bin
eth1</command> it won't work. The easy way to do this at boot up is to make an init
script to load the dhcp address to the correct interface, which should be placed in
<filename>/etc/init.d</filename>. Then run <command>update-rc.d</command> as root with
the correct arguments (see <command>man update-rc.d</command>). </para>
</sect4>
<sect4 id="rh"> <title>Red Hat</title> <para> The file to
edit will of the form <filename>ifcfg-ethX</filename>, located in
<filename>/etc/sysconfig/network-scripts/</filename>. The contents are typically of
the form:</para>
<para> <screen> DEVICE=eth1
# Device name. This is the interface your cable modem will use.
ONBOOT=yes
# load at boot BOOTPROTO=dhcp
# sets the device to receive an IP address from a DHCP server
HWADDR=00:04:BD:DE:42:0B
# the hardware MAC </screen> </para>
<para> Edit the relevant sections with your
favorite text editor program as root to reflect your interface name and MAC and
save it. If the file doesn't exist for the interface you need you can create it,
for example <filename>ifcfg-eth1</filename>. You can then use <command>ifconfig eth1
up</command> from the command line to use it immediately. Upon reboot the correct
hardware settings should be loaded automatically.</para>
</sect4>
<sect4 id="slackware">
<title>Slackware</title>
<para> Slackware has a configuration utility named 'netconfig' that you can use at the command line as root to modify your network settings and configure interfaces by static IP addresses or dhcp. You can rerun it at any time to reconfigure things once you have installed your modem. </para>
</sect4>
<sect4 id="others">
<title>Other Distributions</title>
<para> Feel free to contribute if you have
distribution-specific information to add; see <xref linkend="feedback">. Consult your
distribution documentation where appropriate.</para>
</sect4>
</sect3>
</sect2>
<sect2 id="usb"> <title>Using the USB interface instead of an Ethernet card</title>
<sect3 id="cdce"> <title>USB CDCEther</title>
<para> If you wish to use the USB
interface to accept data you will need USB subsystem support in your kernel as
discussed in <xref linkend="networking">, whether USB-ohci, USB-ehci, or whatever
USB host controller driver required by your system. For a more in-depth discussion
of this, I direct you to the <ulink url="http://www.linux-usb.org/">Linux-USB project
site</ulink>. </para>
<para>In addition the CDCEther (Communications Device Class Ethernet) protocol common to cable modems.</para>
<para>
There are two ways your kernel may support a device driver: either by being statically (always on) compiled within that kernel or loaded (at boot time or later by a script or manually) as a module. You can find out if a driver is statically compiled in the kernel by checking the log of messages at boot up using <command>dmesg | less</command> on the command line. Experienced users may want to take an easier route and check the configuration file for the currently running kernel in <filename>/boot</filename>, usually of the form <filename>config-2.X.x</filename>, which is a text file that can be grepped. On the command line, try <command>grep -e</command> followed by <command>CONFIG_USB_CDCETHER</command> in 2.4.x kernels or <command>CONFIG_USB_ETH</command> in 2.6.x kernels followed by the filename; you should see a '<emphasis>=y</emphasis> or <emphasis>=m</emphasis> at the end of this string for static or modular status, respectively.</para>
<para>The output of <command>dmesg | less</command> should reveal something similar to the following</para>
<para><screen> Mar 2 11:00:52 K7 kernel: CDCEther.c:
0.98.6 7 Jan 2002 Brad Hards and another
Mar 2 11:00:52 K7 kernel: usb.c: registered new driver CDCEther </screen> </para>
<para>in the case of a statically compiled driver or a module loaded at boot.</para>
<para>If you don't see it, to find out if your kernel has already loaded the CDCEther (Communications Device Class Ethernet) driver as a module, on
the command line issue <command>lsmod</command> as root. You should see the module <filename>CDCEther</filename> listed for 2.4.x kernels, or alternatively <filename>usbnet</filename> for 2.6.x kernels.</para>
<para>If you don't see it listed with <command>lsmod</command> try loading the module directly as root;
for kernel 2.4.x this would be of the form <screen> # modprobe CDCEther </screen>
whereas for 2.6.x the command would be <screen> # modprobe usbnet</screen> </para>
<para>If all goes well you should see something like the following at the end of your system log
files (<filename>/var/log/messages</filename> or <filename>/var/log/syslog</filename>, you may need to be root to view these)
or at the end of <command>dmesg | less</command> from the command line:
</para>
<para><screen> Mar 2 11:00:52 K7 kernel: CDCEther.c:
0.98.6 7 Jan 2002 Brad Hards and another
Mar 2 11:00:52 K7 kernel: usb.c: registered new driver CDCEther </screen> </para>
<para> If all goes well you should see something like the following in your system log
files or at the end of <command>dmesg</command>:</para>
<para><screen> Mar 2 11:00:52 K7 kernel: CDCEther.c:
0.98.6 7 Jan 2002 Brad Hards and another
Mar 2 11:00:52 K7 kernel: usb.c: registered new driver CDCEther </screen> </para>
<para> If you are unsuccessful with any of the above, and are determined to
use the USB conduit of this device, you will need to recompile your kernel to support
it. You will need the 2.4.3 kernel or later. For detailed instructions on recompiling
your kernel, I direct you to <ulink url="http://www.tldp.org/HOWTO/Kernel-HOWTO.html">the
Kernel-HOWTO</ulink>. The options required to get USB interface support working on this
device have been addressed in <xref linkend="networking">.
</para>
</sect3> </sect2> </sect1>
<sect1 id="hardware"> <title>Notes on Specific Hardware</title>
<para>Thanks to Jess Portnoy and others for much of the information below. Also, there are some notes specifically pertaining to
configuring a cable modem and cable internet service providers in Israel on <ulink url="http://www.freewebs.com/linuxnet/CableUSBLinuxEn.html">Jess' webpage</ulink> for those that live there. I have personally subscribed to two large cable ISPs in the U.S. without any trouble using the instructions outlined above. The previous incarnation of this document had a large catalogue of ISPs listed by geography, but as a rule the identity of the upstream provider should not affect configuration. If your cable ISP claims not to support linux, it is not because of any technical difficulties related to the operating system. Just don't expect them to configure if for you on your end like they do for most other users (that's why you're reading this document, right?).</para>
<sect2 id="ambit"><title>Ambit Modems</title><para>Supported by Ethernet and CDCEther.</para>
</sect2>
<sect2 id="broadcom"><title>Broadcom Cable Modems</title><para>Supported by Ethernet and CDCEther.</para>
</sect2>
<sect2 id="ericson"><title>Ericson PipeRider Modems</title><para>Supported by Ethernet and CDCEther.</para>
</sect2>
<sect2 id="motorola"> <title>Motorola SurfBoard Modems</title> <para>This model has enjoyed widespread use by cable providers. There is a separate <ulink
url="http://tldp.org/HOWTO/Motorola-Surfboard-Modem/index.html">HOWTO,</ulink>
written by your humble author. Supported by both Ethernet and USB CDCEther. Refer to that document for any hardware
specific questions. The generic instructions above generally work.</para>
</sect2>
<sect2 id="RCA"><title>RCA (Tompson) Modems</title><para>Supported with Ethernet, CDCEther untested.</para>
</sect2>
<sect2 id="terayon"><title>Terayon Modems</title><para>At minimum the tj715 is known to be supported using Ethernet and CDCEther.</para>
</sect2>
<sect2 id="toshiba"> <title>Toshiba PCX-XXXX Cable Modems</title> <para>The four X's in the name indicate model number. Works with Ethernet, CDCEther untested.
'out-of-the-box' with the above instructions. </para>
</sect2>
<sect2 id="WebStar"><title>Webstar Modems</title><para>Supported with Ethernet, CDCEther untested.</para>
</sect2>
</sect1>
<sect1 id="troubleshooting"> <title>Troubleshooting</title> <para> Q: I get kicked
offline about once every 4 days, for no apparent reason, and get the following error,
or something similar, in the kernel log:
<screen> Feb 20 10:05:12 K7 kernel: CDCEther.c: rx status -110 Feb 20 10:05:12 K7 kernel:
CDCEther.c: no repsonse in BULK IN Feb 20 10:05:12 K7 kernel: CDCEther.c: rx status -110
Feb 20 10:05:12 K7 kernel: CDCEther.c: no repsonse in BULK IN Feb 20 10:05:12 K7 kernel:
CDCEther.c: rx status -110 Feb 20 10:05:12 K7 kernel: CDCEther.c: no repsonse in BULK
IN Feb 20 10:05:12 K7 kernel: CDCEther.c: rx status -110 </screen> </para> <para> A:
There are a number of reasons this may be happening, and future updates to the CDCEther
driver may solve some of them. At least one user on the Linux-USB-user mailing list
noticed that on at least one occasion data sent to the modem from upstream by the
cable provider has triggered it. Also, the modem itself is very sensitive to power
interruptions and can lose the connection if this occurs. The fix is to run <command>
ifdown ethX</command>, where <emphasis>ethX</emphasis> is the Ethernet interface (eth0,
eth1 etc.) to clear out any remaining settings that are hung, then remove the module with
<command> rmmod CDCEther</command>, reinsert the CDCEther module and then <command>ifup
ethX </command>. A reboot may be necessary if this doesn't fix the problem. If none
of these work you probably have a real service interruption.</para> <para> Q: I get
the following messages on boot-up; are they errors? </para><para><screen> Can't use
SetEthernetMulticastFilters request Mar 2 11:00:52 K7 kernel: CDCEther.c: Ethernet
information found at device configuration. Trying to use it anyway. Mar 2 11:00:52
K7 kernel: CDCEther.c: Imperfect filtering support - need sw hashing </screen> </para>
<para> A: No. The multicast message is pertaining to Multicast support in the kernel,
which is optional and not necessary for the proper functioning of this modem. The message
about 'Ethernet Information' is a design bug in the modem and can be ignored. As for the
'Imperfect filtering support, to quote Brad Hards: </para> <para><quote>This is a bit
difficult to explain - I assume that you know what multicasting is - when you join a
multicast group, this can be handled by the networking device so that other multicast
traffic doesn't cause interrupts. That is called 'perfect filtering.' However sometimes
the number of multicast addresses exceeds the number of filters that you have. This
leads to 'imperfect filtering,' which can cut down the number of interrupts, but you
still need to do some work in the networking stack. Then you get to the typical cable
modem implementation, and there is not filtering at all. Every multicast packet goes
to the host to be filtered. This doesn't normally matter though, because the cable
modem is a point to point link.</quote> </para> </sect1>
<appendix id="appendix"> <title>Gnu Free Documentation License</title> <para>
Version 1.2, November 2002 </para> <para> Copyright (C) 2000,2001,2002 Free Software
Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Everyone
is permitted to copy and distribute verbatim copies of this license document, but
changing it is not allowed. </para> <para> 0. PREAMBLE </para> <para> The purpose of
this License is to make a manual, textbook, or other functional and useful document
"free" in the sense of freedom: to assure everyone the effective freedom to copy and
redistribute it, with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way to get credit
for their work, while not being considered responsible for modifications made by others.
</para> <para> This License is a kind of "copyleft", which means that derivative works
of the document must themselves be free in the same sense. It complements the GNU
General Public License, which is a copyleft
cense designed for free software. </para> <para> We have designed this License
in order to use it for manuals for free software, because free software needs free
documentation: a free program should come with manuals providing the same freedoms
that the software does. But this License is not limited to software manuals; it can
be used for any textual work, regardless of subject matter or whether it is published
as a printed book. We recommend this License principally for works whose purpose is
instruction or reference. </para> <para>
1. APPLICABILITY AND DEFINITIONS </para> <para> This License applies to any manual
or other work, in any medium, that contains a notice placed by the copyright holder
saying it can be distributed under the terms of this License. Such a notice grants
a world-wide, royalty-free license, unlimited in duration, to use that work under the
conditions stated herein. The "Document", below, refers to any such manual or work.
Any member of the public is a licensee, and is addressed as "you". You accept the
license if you copy, modify or distribute the work in a way requiring permission under
copyright law. </para> <para> A "Modified Version" of the Document means any work
containing the Document or a portion of it, either copied verbatim, or with modifications
and/or translated into another language. </para> <para> A "Secondary Section" is a
named appendix or a front-matter section of the Document that deals exclusively with
the relationship of the publishers or authors of the Document to the Document's overall
subject (or to related matters) and contains nothing that could fall directly within
that overall subject. (Thus, if the Document is in part a textbook of mathematics,
a Secondary Section may not explain any mathematics.) The relationship could be a
matter of historical connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding them. </para> <para>
The "Invariant Sections" are certain Secondary Sections whose titles are designated, as
being those of Invariant Sections, in the notice that says that the Document is released
under this License. If a section does not fit the above definition of Secondary then it
is not allowed to be designated as Invariant. The Document may contain zero Invariant
Sections. If the Document does not identify any Invariant Sections then there are none.
</para> <para> The "Cover Texts" are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is
released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover
Text may be at most 25 words. </para> <para> A "Transparent" copy of the Document means
a machine-readable copy, represented in a format whose specification is available to
the general public, that is suitable for revising the document straightforwardly with
generic text editors or (for images composed of pixels) generic paint programs or
(for drawings) some widely available drawing editor, and that is suitable for input
to text formatters or for automatic translation to a variety of formats suitable for
input to text formatters. A copy made in an otherwise Transparent file format whose
markup, or absence of markup, has been arranged to thwart or discourage subsequent
modification by readers is not Transparent. An image format is not Transparent if
used for any substantial amount of text. A copy that is not "Transparent" is called
"Opaque". </para> <para> Examples of suitable formats for Transparent copies include
plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML
using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF
designed for human modification. Examples of transparent image formats include PNG,
XCF and JPG. Opaque formats include proprietary formats that can be read and edited
only by proprietary word processors, SGML or XML for which the DTD and/or processing
tools are not generally available, and the machine-generated HTML, PostScript or
PDF produced by some word processors for output purposes only. </para> <para> The
"Title Page" means, for a printed book, the title page itself, plus such following
pages as are needed to hold, legibly, the material this License requires to appear
in the title page. For works in formats which do not have any title page as such,
"Title Page" means the text near the most prominent appearance of the work's title,
preceding the beginning of the body of the text. </para> <para> A section "Entitled
XYZ" means a named subunit of the Document whose title either is precisely XYZ or
contains XYZ in parentheses following text that translates XYZ in another language.
(Here XYZ stands for a specific section name mentioned below, such as "Acknowledgements",
"Dedications", "Endorsements", or "History".) To "Preserve the Title" of such a section
when you modify the Document means that it remains a section "Entitled XYZ" according
to this definition. </para> <para> The Document may include Warranty Disclaimers next
to the notice which states that this License applies to the Document. These Warranty
Disclaimers are considered to be included by reference in this License, but only as
regards disclaiming warranties: any other implication that these Warranty Disclaimers
may have is void and has no effect on the meaning of this License. </para> <para>
2. VERBATIM COPYING </para> <para> You may copy and distribute the Document in
any medium, either commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies to the Document
are reproduced in all copies, and that you add no other conditions whatsoever to
those of this License. You may not use technical measures to obstruct or control
the reading or further copying of the copies you make or distribute. However, you
may accept compensation in exchange for copies. If you distribute a large enough
number of copies you must also follow the conditions in section 3. </para> <para>
You may also lend copies, under the same conditions stated above, and you may publicly
display copies. </para> <para>
3. COPYING IN QUANTITY </para> <para> If you publish printed copies (or copies in
media that commonly have printed covers) of the Document, numbering more than 100,
and the Document's license notice requires Cover Texts, you must enclose the copies
in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts
on the front cover, and Back-Cover Texts on the back cover. Both covers must also
clearly and legibly identify you as the publisher of these copies. The front cover
must present the full title with all words of the title equally prominent and visible.
You may add other material on the covers in addition. Copying with changes limited
to the covers, as long as they preserve the title of the Document and satisfy these
conditions, can be treated as verbatim copying in other respects. </para> <para> If
the required texts for either cover are too voluminous to fit legibly, you should put
the first ones listed (as many as fit reasonably) on the actual cover, and continue the
rest onto adjacent pages. </para> <para> If you publish or distribute Opaque copies
of the Document numbering more than 100, you must either include a machine-readable
Transparent copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using public has access
to download using public-standard network protocols a complete Transparent copy of
the Document, free of added material. If you use the latter option, you must take
reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to
ensure that this Transparent copy will remain thus accessible at the stated location
until at least one year after the last time you distribute an Opaque copy (directly
or through your agents or retailers) of that edition to the public. </para> <para>
It is requested, but not required, that you contact the authors of the Document well
before redistributing any large number of copies, to give them a chance to provide
you with an updated version of the Document. </para> <para>
4. MODIFICATIONS </para> <para> You may copy and distribute a Modified Version of the
Document under the conditions of sections 2 and 3 above, provided that you release the
Modified Version under precisely this License, with the Modified Version filling the role
of the Document, thus licensing distribution and modification of the Modified Version to
whoever possesses a copy of it. In addition, you must do these things in the Modified
Version: </para> <para> A. Use in the Title Page (and on the covers, if any) a title
distinct from that of the Document, and from those of previous versions (which should, if
there were any, be listed in the History section of the Document). You may use the same
title as a previous version if the original publisher of that version gives permission.
</para> <para> B. List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified Version, together with
at least five of the principal authors of the Document (all of its principal authors,
if it has fewer than five), unless they release you from this requirement. </para>
<para> C. State on the Title page the name of the publisher of the Modified Version,
as the publisher. </para> <para> D. Preserve all the copyright notices of the Document.
</para> <para> E. Add an appropriate copyright notice for your modifications adjacent to
the other copyright notices. </para> <para> F. Include, immediately after the copyright
notices, a license notice giving the public permission to use the Modified Version
under the terms of this License, in the form shown in the Addendum below. </para>
<para> G. Preserve in that license notice the full lists of Invariant Sections and
required Cover Texts given in the Document's license notice. </para> <para> H. Include
an unaltered copy of this License. </para> <para> I. Preserve the section Entitled
"History", Preserve its Title, and add to it an item stating at least the title, year,
new authors, and publisher of the Modified Version as given on the Title Page. If there
is no section Entitled "History" in the Document, create one stating the title, year,
authors, and publisher of the Document as given on its Title Page, then add an item
describing the Modified Version as stated in the previous sentence. </para> <para>
J. Preserve the network location, if any, given in the Document for public access to
a Transparent copy of the Document, and likewise the network locations given in the
Document for previous versions it was based on. These may be placed in the "History"
section. You may omit a network location for a work that was published at least four
years before the Document itself, or if the original publisher of the version it refers
to gives permission. </para> <para> K. For any section Entitled "Acknowledgements"
or "Dedications", Preserve the Title of the section, and preserve in the section all
the substance and tone of each of the contributor acknowledgements and/or dedications
given therein. </para> <para> L. Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers or the equivalent are
not considered part of the section titles. </para> <para> M. Delete any section
Entitled "Endorsements". Such a section may not be included in the Modified Version.
</para> <para> N. Do not retitle any existing section to be Entitled "Endorsements"
or to conflict in title with any Invariant Section. </para> <para> O. Preserve any
Warranty Disclaimers. If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material copied from the
Document, you may at your option designate some or all of these sections as invariant.
To do this, add their titles to the list of Invariant Sections in the Modified Version's
license notice. These titles must be distinct from any other section titles. You may
add a section Entitled "Endorsements", provided it contains nothing but endorsements
of your Modified Version by various parties--for example, statements of peer review or
that the text has been approved by an organization as the authoritative definition of
a standard. </para> <para> You may add a passage of up to five words as a Front-Cover
Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one
of Back-Cover Text may be added by (or through arrangements made by) any one entity.
If the Document already includes a cover text for the same cover, previously added by
you or by arrangement made by the same entity you are acting on behalf of, you may not
add another; but you may replace the old one, on explicit permission from the previous
publisher that added the old one. </para> <para> The author(s) and publisher(s) of the
Document do not by this License give permission to use their names for publicity for or
to assert or imply endorsement of any Modified Version. </para> <para> 5. COMBINING
DOCUMENTS </para> <para> You may combine the Document with other documents released
under this License, under the terms defined in section 4 above for modified versions,
provided that you include in the combination all of the Invariant Sections of all of the
original documents, unmodified, and list them all as Invariant Sections of your combined
work in its license notice, and that you preserve all their Warranty Disclaimers.
</para> <para> The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single copy. If there
are multiple Invariant Sections with the same name but different contents, make the
title of each such section unique by adding at the end of it, in parentheses, the name
of the original author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of Invariant Sections in the
license notice of the combined work. </para> <para> In the combination, you must combine
any sections Entitled "History" in the various original documents, forming one section
Entitled "History"; likewise combine any sections Entitled "Acknowledgements", and any
sections Entitled "Dedications". You must delete all sections Entitled "Endorsements".
</para> <para> 6. COLLECTIONS OF DOCUMENTS </para> <para> You may make a collection
consisting of the Document and other documents released under this License, and replace
the individual copies of this License in the various documents with a single copy that
is included in the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects. </para> <para> You
may extract a single document from such a collection, and distribute it individually
under this License, provided you insert a copy of this License into the extracted
document, and follow this License in all other respects regarding verbatim copying of
that document. </para> <para> 7. AGGREGATION WITH INDEPENDENT WORKS </para> <para>
A compilation of the Document or its derivatives with other separate and independent
documents or works, in or on a volume of a storage or distribution medium, is called
an "aggregate" if the copyright resulting from the compilation is not used to limit
the legal rights of the compilation's users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not apply to the
other works in the aggregate which are not themselves derivative works of the Document.
</para> <para> If the Cover Text requirement of section 3 is applicable to these copies
of the Document, then if the Document is less than one half of the entire aggregate,
the Document's Cover Texts may be placed on covers that bracket the Document within the
aggregate, or the electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole aggregate. </para>
<para> 8. TRANSLATION </para> <para> Translation is considered a kind of modification, so
you may distribute translations of the Document under the terms of section 4. Replacing
Invariant Sections with translations requires special permission from their copyright
holders, but you may include translations of some or all Invariant Sections in addition
to the original versions of these Invariant Sections. You may include a translation of
this License, and all the license notices in the Document, and any Warranty Disclaimers,
provided that you also include the original English version of this License and the
original versions of those notices and disclaimers. In case of a disagreement between
the translation and the original version of this License or a notice or disclaimer,
the original version will prevail. </para> <para> If a section in the Document is
Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4)
to Preserve its Title (section 1) will typically require changing the actual title.
</para> <para> 9. TERMINATION </para> <para> You may not copy, modify, sublicense,
or distribute the Document except as expressly provided for under this License.
Any other attempt to copy, modify, sublicense or distribute the Document is void,
and will automatically terminate your rights under this License. However, parties
who have received copies, or rights, from you under this License will not have their
licenses terminated so long as such parties remain in full compliance. </para> <para>
10. FUTURE REVISIONS OF THIS LICENSE </para> <para> The Free Software Foundation may
publish new, revised versions of the GNU Free Documentation License from time to time.
Such new versions will be similar in spirit to the present version, but may differ
in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.
</para> <para> Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this License "or any
later version" applies to it, you have the option of following the terms and conditions
either of that specified version or of any later version that has been published (not as
a draft) by the Free Software Foundation. If the Document does not specify a version
number of this License, you may choose any version ever published (not as a draft)
by the Free Software Foundation. </para> <para> ADDENDUM: How to use this License
for your documents </para> <para> To use this License in a document you have written,
include a copy of the License in the document and put the following copyright and
license notices just after the title page: </para> <para> Copyright (c) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document under the terms
of the GNU Free Documentation License, Version 1.2 or any later version published
by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts,
and no Back-Cover Texts. A copy of the license is included in the section entitled
"GNU Free Documentation License". </para> <para> If you have Invariant Sections,
Front-Cover Texts and Back-Cover Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being
LIST, and with the Back-Cover Texts being LIST. If you have Invariant Sections without
Cover Texts, or some other combination of the three, merge those two alternatives to
suit the situation. </para> <para> If your document contains nontrivial examples of
program code, we recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License, to permit their use in
free software. </para> </appendix> <!-- Section1: examples: END -->
</article>
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