doc/en/home-router-howto.xml

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/home-router-howto.xml,v 1.38 2005/12/12 04:36:21 vapier Exp $ -->

<guide link="/doc/en/home-router-howto.xml" lang="en">
<title>Home Router Guide</title>

<author title="Author">
  <mail link="vapier@gentoo.org">Mike Frysinger</mail>
</author>

<abstract>
This document details how to turn an old Gentoo machine into a router 
for connecting your home network to the internet.
</abstract>

<!-- The content of this document is released into the public domain -->
<license/>

<version>1.23</version>
<date>2005-12-11</date>

<chapter>
<title>Introduction</title>
<section>
<body>

<p>
Building your own router out of old spare parts has many advantages over buying
a pre-made canned router by say Linksys.  The biggest one by far is control
over the connection.  The other advantages are left up to your imagination;
just about anything can be done in this scenario, it's just a matter of needing
it.
</p>

<p>
This guide will show you how to setup Network Address Translation (NAT) on the
router (kernel and iptables), add and configure common services (Domain Name
System (DNS) via dnsmasq, dhcp via dhcpcd, ADSL via rp-pppoe), and conclude
with more elaborate and fun things that can be done (port forwarding, traffic
shaping, proxies/caching, etc...).
</p>

<p>
Before getting started, there's a few basic requirements you must meet.  First,
you'll need a computer that has at least 2 Network Interface Cards (NICs) in
it.  Next, you'll need the configuration settings for your internet connection
(may include things like IP/DNS/Gateway/username/password).  Finally, you'll
need a bit of spare time and some Gentoo loving.
</p>

<p>
The conventions used in this guide are:
</p>

<ul>
 <li>eth0 - NIC connected to the Local Area Network (LAN)</li>
 <li>eth1 - NIC connected to the Wide Area Network (WAN)</li>
 <li>LAN utilizes the private 192.168.0.xxx network</li>
 <li>router is hardcoded to the standard 192.168.0.1 IP</li>
 <li>router is running Linux 2.4 or 2.6; you're on your own with 2.0/2.2</li>
</ul>

<impo>
Due to security precautions, I would highly suggest you shut down any unneeded
services on the router until we have a chance to get the firewall up and
rolling.  To view the currently running services, just run <c>rc-status</c>.
</impo>

</body>
</section>
</chapter>

<chapter>
<title>Kernel setup (know thyself first)</title>
<section>
<body>

<p>
Your kernel needs to have the drivers running for both your NICs.  To see if
your cards are already setup, just run <c>ifconfig</c>.  Your output may differ
slightly from the following, that's fine.  What matters is that the interface
shows up at all.
</p>

<pre caption="Checking NICs">
# <i>ifconfig -a</i>
eth0      Link encap:Ethernet  HWaddr 00:60:F5:07:07:B8
          BROADCAST 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:1000 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
          Interrupt:11 Base address:0x9800 

eth1      Link encap:Ethernet  HWaddr 00:60:F5:07:07:B9
          BROADCAST 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:1000 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
          Interrupt:10 Base address:0x9400 
</pre>

<p>
If you do not see your two cards showing up and you're not sure what kind of
cards you have, try running <c>lspci</c>.  You can get that from <c>emerge
pciutils</c>.  Look for "Ethernet controller" in the output.  Once you have
this information, go into your kernel and add support for the correct drivers.
</p>

<p>
The next thing you'll need is support for iptables and NAT (and packet shaping
if you want).  The following list is split up into always required (*), 
required only for adsl via PPPoE (a), suggested for everyone (x), and only 
for shaper (s) features.  It does not matter whether you build the features 
into the kernel or as a module so long as when the feature is needed, the 
correct module(s) are loaded (module loading is left to the reader as a fun 
exercise however).
</p>

<pre caption="Network Options">
Networking options  ---&gt;
   [*] TCP/IP networking
      [*] IP: advanced router
   [*] Network packet filtering (replaces ipchains)
<comment>If you use 2.4.x, you have to enable the following for DHCP:</comment>
   [*] Socket Filtering

   IP: Netfilter Configuration  ---&gt;
      [*] Connection tracking (required for masq/NAT)
         [x] FTP protocol support
         [x] IRC protocol support
      [*] IP tables support (required for filtering/masq/NAT)
         [*] IP range match support
         [x] MAC address match support
         [*] Multiple port match support
         [*] Packet filtering
            [*] REJECT target support
            [x] REDIRECT target support
         [*] Full NAT
            [*] MASQUERADE target support
         [s] Packet mangling
            [s] MARK target support
         [x] LOG target support

   QoS and/or fair queueing  ---&gt;
      [s] QoS and/or fair queueing
         [s] HTB packet scheduler
         [s] Ingress Qdisc

   [a] PPP (point-to-point protocol) support
      [a] PPP filtering
      [a] PPP support for async serial ports
      [a] PPP support for sync tty ports
      [a] PPP Deflate compression
      [a] PPP BSD-Compress compression
      [a] PPP over Ethernet
</pre>

<note>
Somethings may be slightly different in a 2.4 vs 2.6 kernel, but you should be
able to figure it out :).
</note>

</body>
</section>
</chapter>

<chapter>
<title>Hug the WAN (a.k.a. The Internet)</title>

<section>
<title>Intro</title>
<body>

<p>
There are many ways to connect to the internet so I'll just cover the ones I'm
familiar with.  That leaves us with ADSL (PPPoE) and cable modems
(static/dynamic).  If there are other methods out there, feel free to write up
a little blurb and e-mail me.  Feel free to skip any of the following sections
in this chapter that don't apply to you.  This chapter is just about getting
the router connected to the internet via eth1.
</p>

</body>
</section>
<section>
<title>ADSL and PPPoE</title>
<body>

<p>
All the fancy PPPoE software has been bundled up into one little nice package
nowadays called <uri link="http://www.roaringpenguin.com/">Roaring
Penguin</uri>.  Simply <c>emerge rp-pppoe</c> and you'll be on your way.
Remember how I said you'll need username/password information?  Well I wasn't
lying so I hope you have it now!  Load up <path>/etc/ppp/pppoe.conf</path> in
your favorite editor and set it up.
</p>

<note>
In order for the following net settings to work, you must have 
baselayout-1.11.14 or later installed on your system.
</note>

<pre caption="Setting up eth1">
<comment>(Replace 'vla9h924' with your username and 'password' with your password)</comment>

# <i>nano /etc/ppp/pap-secrets</i>
<comment># client    server  secret</comment>
"vla9h924" * "password"
# <i>nano /etc/conf.d/net</i>
<comment>Tell baselayout to use adsl for your eth1:</comment>
config_eth1=( "adsl" )
user_eth1=( "vla9h924" )
# <i>ln -s net.lo /etc/init.d/net.eth1</i>
# <i>rc-update add net.eth1 default</i>
# <i>/etc/init.d/net.eth1 start</i>
</pre>

<warn>
When the DSL interface comes up, it will create ppp0.  Although your NIC is 
called eth1, the IP is actually bound to ppp0.  From now on, when you see 
examples that utilize 'eth1', substitute with 'ppp0'.
</warn>

</body>
</section>

<section>
<title>Cable and/or dynamic/static IP</title>
<body>

<p>
If you have a static IP then you will need a few more details than if 
you have a dynamic IP.  For static users, you will need your IP, 
gateway, and DNS servers.
</p>

<pre caption="Setting up eth1">
<comment>Dynamic IP Users:</comment>
# <i>emerge dhcpcd</i>
# <i>nano /etc/conf.d/net</i>
<comment>You'll need an entry like so:</comment>
config_eth1=( "dhcp" )

<comment>Static IP Users:</comment>
# <i>nano /etc/conf.d/net</i>
<comment>You'll need entries like so:</comment>
ifconfig_eth1=( "66.92.78.102 broadcast 66.92.78.255 netmask 255.255.255.0" )
routes_eth1=( "default gw 66.92.78.1" )
# <i>nano /etc/resolv.conf</i>
<comment>Add one line per DNS server:</comment>
nameserver 123.123.123.123

<comment>Dynamic and Static Setup:</comment>
# <i>ln -s net.lo /etc/init.d/net.eth1</i>
# <i>rc-update add net.eth1 default</i>
# <i>/etc/init.d/net.eth1 start</i>
</pre>

<p>
You should be all set to go now.
</p>

</body>
</section>
</chapter>

<chapter>
<title>Hug the LAN (bring along some friends)</title>
<section>
<body>

<p>
This step is a breeze compared to the previous one.
</p>

<pre caption="Setting up eth0">
# <i>nano /etc/conf.d/net</i>
<comment>Add a line like the following:</comment>
ifconfig_eth0=( "192.168.0.1 broadcast 192.168.0.255 netmask 255.255.255.0" )
# <i>rc-update add net.eth0 default</i>
# <i>/etc/init.d/net.eth0 start</i>
</pre>

</body>
</section>
</chapter>

<chapter>
<title>LAN Services (because we're nice people)</title>

<section>
<title>DHCP Server</title>
<body>

<p>
I bet it'd be nice if everyone else in your house could just plug their
computers into the network and things would just work.  No need to remember
mind-numbing details or make them stare at confusing configuration screens!
Life would be grand eh?  Introducing the Dynamic Host Configuration Protocol
(DHCP) and why you should care.
</p>

<p>
DHCP is exactly what its name implies.  It's a protocol that allows you 
to dynamically configure other hosts automatically.  You run a DHCP server on
the router, give it all the information about your network (valid IPs,
DNS servers, gateways, etc...), and then when the other hosts start up, they
run a DHCP client to automatically configure themselves.  No fuss, no muss!
For more information about DHCP, you can always visit <uri
link="http://en.wikipedia.org/wiki/DHCP">Wikipedia</uri>.
</p>

<p>
We'll use a package called dnsmasq which provides both DHCP and DNS services.
For now lets just focus on the DHCP aspect.  Note that if you want to run a
different DHCP server, you can find another example in the Fun Things chapter.
Also, if you wish to tinker with the DHCP server settings, just read the 
comments in <path>/etc/dnsmasq.conf</path>.  All the defaults should work fine 
though.
</p>

<pre caption="Setting up a DHCP server">
# <i>emerge dnsmasq</i>
# <i>nano /etc/dnsmasq.conf</i>
<comment>You should need to just add this one line:</comment>
dhcp-range=192.168.0.100,192.168.0.250,72h

# <i>nano /etc/conf.d/dnsmasq</i>
<comment>Add "-i eth0" to DNSMASQ_OPTS</comment>
# <i>rc-update add dnsmasq default</i>
# <i>/etc/init.d/dnsmasq start</i>
</pre>

<p>
Now your little router is a bona-fide DHCP server!  Plugin those computers and
watch them work!  With Windows systems you should go into the TCP/IP Properties
and select the 'Obtain an IP address automatically' and 'Obtain DNS server
address automatically' options.  Sometimes the changes aren't instantaneous, so
you may have to open a command prompt and run <c>ipconfig /release</c> and
<c>ipconfig /renew</c>.  But enough about Windows, let's get back to our
favorite penguin.
</p>

</body>
</section>

<section>
<title>DNS Server</title>
<body>

<p>
When people want to visit a place on the internet, they remember names, not a
string of funky numbers.  After all, what's easier to remember, ebay.com or
66.135.192.87?  This is where the DNS steps in.  DNS servers run all over the
internet, and whenever someone wants to visit 'ebay.com', these servers turn
'ebay.com' (what we understand) into '66.135.192.87' (what our computers
understand).  For more information about DNS, you can always visit <uri
link="http://en.wikipedia.org/wiki/DNS">Wikipedia</uri>.
</p>

<p>
Since we're using dnsmasq for our DHCP server, and it includes a DNS server,
you've got nothing left to do here!  Your little router is already providing
DNS to its DHCP clients.  Bet you wish everything was this easy ;).
</p>

<p>
You're welcome to choose other DNS servers if you're more comfortable with 
them, but the reason dnsmasq is great is because it was designed to do exactly 
what we want and nothing more.  It's a little DNS caching/forwarding server for 
local networks.  We're not looking to provide DNS for our own domain here, just 
offer simple DNS services to everyone else on our LAN.
</p>

</body>
</section>

<section>
<title>NAT (a.k.a. IP-masquerading)</title>
<body>

<p>
At this point, people on your network can talk to each other and they can look
up hostnames via DNS, but they still can't actually connect to the internet.
While you may think that's great (more bandwidth for you!), I bet they're not
too happy just yet.
</p>

<p>
This is where Network Address Translation (NAT) steps in.  NAT is a way of 
connecting multiple computers in a private LAN to the internet when you have a 
smaller number of public IP addresses available to you.  Typically you are given 
1 IP by your ISP, but you want to let your whole house connect to the internet.
NAT is the magic that makes this possible.  For more information about NAT, you 
can always visit <uri link="http://en.wikipedia.org/wiki/NAT">Wikipedia</uri>.
</p>

<note>
Before we get started, make sure you have iptables on your system.  Although it
is automatically installed on most systems, you may not have it.  If you don't,
just run <c>emerge iptables</c>.
</note>

<pre caption="Setting up iptables">
<comment>First we flush our current rules</comment>
# <i>iptables -F</i>
# <i>iptables -t nat -F</i>

<comment>Setup default policies to handle unmatched traffic</comment>
# <i>iptables -P INPUT ACCEPT</i>
# <i>iptables -P OUTPUT ACCEPT</i>
# <i>iptables -P FORWARD DROP</i>

<comment>Copy and paste these examples ...</comment>
# <i>export LAN=eth0</i>
# <i>export WAN=eth1</i>

<comment>Then we lock our services so they only work from the LAN</comment>
# <i>iptables -I INPUT 1 -i ${LAN} -j ACCEPT</i>
# <i>iptables -I INPUT 1 -i lo -j ACCEPT</i>
# <i>iptables -A INPUT -p UDP --dport bootps -i ! ${LAN} -j REJECT</i>
# <i>iptables -A INPUT -p UDP --dport domain -i ! ${LAN} -j REJECT</i>

<comment>(Optional) Allow access to our ssh server from the WAN</comment>
# <i>iptables -A INPUT -p TCP --dport ssh -i ${WAN} -j ACCEPT</i>

<comment>Drop TCP / UDP packets to privileged ports</comment>
# <i>iptables -A INPUT -p TCP -i ! ${LAN} -d 0/0 --dport 0:1023 -j DROP</i>
# <i>iptables -A INPUT -p UDP -i ! ${LAN} -d 0/0 --dport 0:1023 -j DROP</i>

<comment>Finally we add the rules for NAT</comment>
# <i>iptables -I FORWARD -i ${LAN} -d 192.168.0.0/255.255.0.0 -j DROP</i>
# <i>iptables -A FORWARD -i ${LAN} -s 192.168.0.0/255.255.0.0 -j ACCEPT</i>
# <i>iptables -A FORWARD -i ${WAN} -d 192.168.0.0/255.255.0.0 -j ACCEPT</i>
# <i>iptables -t nat -A POSTROUTING -o ${WAN} -j MASQUERADE</i>
<comment>Tell the kernel that ip forwarding is OK</comment>
# <i>echo 1 > /proc/sys/net/ipv4/ip_forward</i>
# <i>for f in /proc/sys/net/ipv4/conf/*/rp_filter ; do echo 1 > $f ; done</i>

<comment>This is so when we boot we don't have to run the rules by hand</comment>
# <i>/etc/init.d/iptables save</i>
# <i>rc-update add iptables default</i>
# <i>nano /etc/sysctl.conf</i>
<comment>Add/Uncomment the following lines:
net.ipv4.ip_forward = 1
net.ipv4.conf.default.rp_filter = 1</comment>
</pre>

<p>
Once you've typed out all of that, the rest of your network should now be able
to use the internet as if they were directly connected themselves.  
</p>

</body>
</section>
</chapter>

<chapter>
<title>Fun Things (for a rainy day)</title>

<section>
<title>Intro</title>
<body>

<p>
Believe it or not, you're done :).  From here on out, I'll cover a bunch of
common topics that may interest you.  Everything in this chapter is completely
optional.
</p>

</body>
</section>

<section>
<title>Port Forwarding</title>
<body>

<p>
Sometimes you would like to be able to host services on a computer behind the
router, or just to make your life easier when connecting remotely.  Perhaps you
want to run a FTP, HTTP, SSH, or VNC server on one or more machines behind your
router and be able to connect to them all.  The only caveat is that you can
only have one service/machine combo per port.  For example, there is no
practical way to setup three FTP servers behind your router and then try to
connect to them all through port 21; only one can be on port 21 while the
others would have to be on say port 123 and port 567.
</p>

<p>
All the port forwarding rules are of the form <c>iptables -t nat -A PREROUTING
[-p protocol] --dport [external port on router] -i ${WAN} -j DNAT --to [ip/port
to forward to]</c>.  Unfortunately, iptables does not accept hostnames when port
forwarding.  If you are forwarding an external port to the same port on the 
internal machine, you can omit the destination port.  See the iptables(8) man 
page for more information.
</p>

<pre caption="Running the iptables commands">
<comment>Copy and paste these examples ...</comment>
# <i>export LAN=eth0</i>
# <i>export WAN=eth1</i>

<comment>Forward port 2 to ssh on an internal host</comment>
# <i>iptables -t nat -A PREROUTING -p tcp --dport 2 -i ${WAN} -j DNAT --to 192.168.0.2:22</i>

<comment>FTP forwarding to an internal host</comment>
# <i>iptables -t nat -A PREROUTING -p tcp --dport 21 -i ${WAN} -j DNAT --to 192.168.0.56</i>

<comment>HTTP forwarding to an internal host</comment>
# <i>iptables -t nat -A PREROUTING -p tcp --dport 80 -i ${WAN} -j DNAT --to 192.168.0.56</i>

<comment>VNC forwarding for internal hosts</comment>
# <i>iptables -t nat -I PREROUTING -p tcp --dport 5900 -i ${WAN} -j DNAT --to 192.168.0.2</i>
# <i>iptables -t nat -I PREROUTING -p tcp --dport 5901 -i ${WAN} -j DNAT --to 192.168.0.3:5900</i>
<comment>If you want to VNC in to 192.168.0.3, then just add ':1' to the router's hostname</comment>

<comment>Bittorrent forwarding</comment>
# <i>iptables -t nat -A PREROUTING -p tcp --dport 6881:6889 -i ${WAN} -j DNAT --to 192.168.0.2</i>

<comment>eDonkey/eMule forwarding</comment>
# <i>iptables -t nat -A PREROUTING -p tcp --dport 4662 -i ${WAN} -j DNAT --to 192.168.0.55</i>

<comment>Game Cube Warp Pipe support</comment>
# <i>iptables -t nat -A PREROUTING -p udp --dport 4000 -i ${WAN} -j DNAT --to 192.168.0.56</i>

<comment>Playstation 2 Online support</comment>
# <i>iptables -t nat -A PREROUTING -p tcp --dport 10070:10080 -i ${WAN} -j DNAT --to 192.168.0.11</i>
# <i>iptables -t nat -A PREROUTING -p udp --dport 10070:10080 -i ${WAN} -j DNAT --to 192.168.0.11</i>

<comment>Xbox Live</comment>
# <i>iptables -t nat -A PREROUTING -p tcp --dport 3074 -i ${WAN} -j DNAT --to 192.168.0.69</i>
# <i>iptables -t nat -A PREROUTING -p udp --dport 3074 -i ${WAN} -j DNAT --to 192.168.0.69</i>
# <i>iptables -t nat -A PREROUTING -p udp --dport 88 -i ${WAN} -j DNAT --to 192.168.0.69</i>
</pre>

<note>
If you have other common / cool examples, please <mail
link="vapier@gentoo.org">e-mail me</mail>.
</note>

</body>
</section>

<section>
<title>Identd (for IRC)</title>
<body>

<p>
Internet Relay Chat utilizes the ident service pretty heavily.  Now that the
IRC clients are behind the router, we need a way to host ident for both the
router and the clients.  One such server has been created called
<c>midentd</c>.
</p>

<pre caption="Setting up ident">
# <i>emerge midentd</i>
# <i>rc-update add midentd default</i>
# <i>/etc/init.d/midentd start</i>
</pre>

<p>
There are a few other ident servers in portage.  Depending on your needs, I
would recommend checking out <c>oidentd</c> and <c>fakeidentd</c>.
</p>

</body>
</section>

<!--
<section>
<title>Traffic Shaping</title>
<body>
<p>
This is an attempt to simply and Gentooify the <uri link="http://www.tldp.org/HOWTO/ADSL-Bandwidth-Management-HOWTO/">ADSL Bandwidth Management HOWTO</uri> 
found over at the TLDP.  Feel free to refer to the original document 
for more details.
</p>

<p>
Here we will be setting up what some people refer to as a "Packet Shaper", 
<uri link="http://en.wikipedia.org/wiki/Traffic_shaping">"Traffic Shaping"</uri>, 
or <uri link="http://en.wikipedia.org/wiki/QoS">"Quality of Service"</uri>.  
Simply put, we want to setup rules on our router that will slow down 
certain activities (like sending large e-mails or downloading from P2P 
networks) while keeping other activities (like browsing the web or playing 
online video games) reasonably fast.  A 30 second difference in a video 
game is a lot worse than a 30 second difference in downloading large 
files :).
</p>

<p>
The first thing is to make sure your kernel has all the features added to 
it.  See the chapter on <uri link="#doc_chap2">Kernel setup</uri> for more 
information.  Next, you will need to <c>emerge iptables iputils</c> so that 
you will have access to the <c>iptables</c>, <c>ip</c>, and <c>tc</c> 
commands.
</p>

<p>
Before we jump into the commands, let's cover a little of the theory.  The 
way this whole system works is to classify common network streams and then 
to prioritize them.  You use iptables to classify network streams, iputils 
to define the different priority levels, and the kernel to adjust speeds.  
Just remember that although you can control outbound traffic pretty tightly 
(from the LAN to the WAN), your ability to control inbound traffic (from 
the WAN to the LAN) is somewhat limited.  Just remember that the following 
examples are to get your feet wet; if you want more then I'd suggest 
reading up on the subject.  In this example, we will be using the 
<uri link="http://luxik.cdi.cz/~devik/qos/htb/">Hierarchical Token Buckets (HTB)</uri> 
packet scheduling algorithm.  Still with me?  Great, let's start shaping :).
</p>

<pre caption="Setup">
DEV=eth1 <comment>NIC connected to WAN</comment>
RATE_OUT=100 <comment>Available outbound bandwidth (in kilobits [kb])</comment>
RATE_IN=1400 <comment>Available inbound bandwidth (in kb)</comment>

<comment>Here we initialize the priority system.  The 45 is used to set the default classification level.</comment>
ip link set dev ${DEV} qlen 30
tc qdisc add dev ${DEV} root handle 1: htb default 45
tc class add dev ${DEV} parent 1: classid 1:1 htb rate ${RATE_OUT}kbit
</pre>

<p>
Here we initialized the system which will be used to prioritize all of 
our network traffic.  We created our queue, told it to use the HTB 
algorithm, and set the default classification level to '45'.  The 
default is completely arbitrary, as are the levels we choose from 
here on out.  The only thing that matters is how the levels compare 
relatively; a level '10' packet will be given preference over a 
level '45' packet.  Let's move on to declaring different levels.
</p>

<pre caption="Declaring levels">
tc class add dev $DEV parent 1:1 classid 1:10 htb rate $rkbit ceil $tkbit prio $p
tc qdisc add dev $DEV parent 1:10 handle 10: sfq
</pre>
</body>
</section>
-->

<section>
<title>Time Server</title>
<body>

<p>
Keeping your system time correct is essential in maintaining a healthy system.
One of the most common ways of accomplishing this is with the Network Time
Protocol (NTP) and the ntp package (which provides implementations for both
server and client).
</p>

<p>
Many people run ntp clients on their computers.  Obviously, the more clients in
the world, the larger the load the ntp servers need to shoulder.  In
environments like home networks though, we can help keep the load down on
public servers while still providing the proper time to all our computers.  As
an added bonus, our private updates will be a lot faster for the clients too!
All we have to do is run a ntp server on our router that synchronizes itself
with the public internet servers while providing the time to the rest of the
computers in the network.  To get started, simply <c>emerge ntp</c> on the
router.
</p>

<pre caption="Setting up the NTP server">
# <i>nano /etc/conf.d/ntp-client</i>
<comment>Customize if you wish but the defaults should be fine</comment>
# <i>rc-update add ntp-client default</i>

# <i>nano /etc/ntp.conf</i>
<comment>Add the follwing lines:</comment>
restrict default ignore
restrict 192.168.0.0 mask 255.255.255.0 notrust nomodify notrap
<comment>These will allow only ntp clients with an IP
address in the 192.168.0.xxx range to use your ntp server</comment>
# <i>nano /etc/conf.d/ntpd</i>
<comment>Customize if you wish but the defaults should be fine</comment>
# <i>rc-update add ntpd default</i>

# <i>/etc/init.d/ntp-client start</i>
# <i>/etc/init.d/ntpd start</i>
</pre>

<note>
You should make sure that you allow inbound and outbound communication on the
ntp port (123/udp) when setting up the server.  The client just needs outbound
access on port 123 over udp.
</note>

<p>
Now, on your clients, have them <c>emerge ntp</c> also.  However, we will just
run the ntp client so setup is a lot simpler.
</p>

<pre caption="Setting up a NTP client">
# <i>nano /etc/conf.d/ntp-client</i>
<comment>Change the 'pool.ntp.org' server in the NTPCLIENT_OPTS variable to '192.168.0.1'</comment>
# <i>rc-update add ntp-client default</i>
# <i>/etc/init.d/ntp-client start</i>
</pre>

</body>
</section>

<section>
<title>Rsync Server</title>
<body>

<p>
For those who run multiple Gentoo boxes on the same lan, you often want to 
keep from having every machine running <c>emerge sync</c> with remote 
servers.  By setting up a local rsync, you save on both your bandwidth and 
the Gentoo rsync servers' bandwidth.  It's pretty simple to do.
</p>
<note>
For a much more in-depth rsync guide, please see the official <uri 
link="/doc/en/rsync.xml#doc_chap4">rsync guide</uri>
</note>

<p>
Since every Gentoo machine requires rsync, theres no need to emerge it.  Edit 
the default <path>/etc/rsyncd.conf</path> config file, uncomment the 
<c>[gentoo-portage]</c> section, and make sure you add an <c>address</c> 
option.  All the other defaults should be fine.
</p>

<pre caption="Rsync server config">
pid file = /var/run/rsyncd.pid
use chroot = yes
read only = yes
address = 192.168.0.1

[gentoo-portage]
        path = /mnt/space/portage
        comment = Gentoo Linux Portage tree
        exclude = /distfiles /packages
</pre>

<p>
Then you need to start the service (again, the defaults are OK).
</p>

<pre caption="Starting the rsync server">
# <i>/etc/init.d/rsyncd start</i>
# <i>rc-update add rsyncd default</i>
</pre>

<p>
Only thing left is to set tell your clients to sync against the router.
</p>

<pre caption="Client SYNC settings in make.conf">
SYNC="rsync://192.168.0.1/gentoo-portage"
</pre>

</body>
</section>

<section>
<title>Mail Server</title>
<body>

<p>
Sometimes it's nice to run your own Simple Mail Transfer Protocol (SMTP) server
on the router.  You may have your own reason for wanting to do so, but I run it
so that the users see mail as being sent instantly and the work of
retrying/routing is left up to the mail server.  Some ISPs also don't allow for
mail relaying for accounts that aren't part of their network (like Verizon).
Also, you can easily throttle the delivery of mail so that large attachments
won't seriously lag your connection for half an hour.
</p>

<pre caption="Setting up SMTP">
# <i>emerge qmail</i>
<comment>make sure the output of `hostname` is correct</comment>
# <i>ebuild /var/db/pkg/*-*/qmail-1.03-r*/*.ebuild config</i>
# <i>iptables -I INPUT -p tcp --dport smtp -i ! ${LAN} -j REJECT</i>
# <i>ln -s /var/qmail/supervise/qmail-send /service/qmail-send</i>
# <i>ln -s /var/qmail/supervise/qmail-smtpd /service/qmail-smtpd</i>
<!--
# <i>cd /etc/tcprules.d</i>
# <i>nano tcp.qmail-smtp</i>
-->
# <i>cd /etc</i>
# <i>nano tcp.smtp</i>
<comment>Add an entry like so to the allow section:</comment>
192.168.0.:allow,RELAYCLIENT=""
<!--
# <i>tcprules tcp.qmail-qmtp.cdb rules.tmp &lt; tcp.qmail-smtp</i>
-->
# <i>tcprules tcp.smtp.cdb rules.tmp &lt; tcp.smtp</i>
# <i>rc-update add svscan default</i>
# <i>/etc/init.d/svscan start</i>
</pre>

<p>
I'm a huge fan of qmail, but you're free to use a different mta :).  When you
setup e-mail on the hosts in your network, tell them that their SMTP server is
192.168.0.1 and everything should be peachy.  You might want to visit the <uri
link="http://qmail.org/">qmail homepage</uri> for more documentation.
</p>

</body>
</section>

<!--
<section>
<title>E-mail Virus Scanning</title>
<body>
<p>
If you'd like to provide e-mail virus scanning for your users, but 
don't want to have to install a virus scanner on every single machine, 
then <c>pop3vscan</c> may just be the thing for you; a transparent 
Post Office Protocol (POP) scanner.
</p>

<pre caption="Setting up pop3vscan">
TODO
</pre>

</body>
</section>
-->

<section>
<title>Full DHCP Server</title>
<body>

<p>
Earlier we used dnsmasq to provide DHCP service to all our clients.  For most
people with a simple small LAN, this is perfect.  But you may need something 
with more features.  Thus we turn to a full-featured DHCP server as provided 
by the <uri link="http://www.isc.org/products/DHCP">ISC</uri> folks.
</p>

<pre caption="Setting up dhcpd">
# <i>emerge dhcp</i>
# <i>nano /etc/dhcp/dhcpd.conf</i>
<comment>(Here is a sample configuration file:)</comment>
authoritative;
ddns-update-style interim;
subnet 192.168.0.0 netmask 255.255.255.0 {
    range 192.168.0.100 192.168.0.250;
    default-lease-time 259200;
    max-lease-time 518400;
    option subnet-mask 255.255.255.0;
    option broadcast-address 192.168.0.255;
    option routers 192.168.0.1;
    option domain-name-servers 192.168.0.1;
}
# <i>nano /etc/conf.d/dhcp</i>
<comment>(Set IFACE="eth0")</comment>
# <i>rc-update add dhcp default</i>
# <i>/etc/init.d/dhcp start</i>
</pre>

<p>
This is the minimal setup required to replace the dnsmasq DHCP functionality 
that we used earlier.  Speaking of which, you did remember to disable the DHCP 
features in dnsmasq didn't you?  If not, you should do so now (just comment 
out the <c>dhcp-range</c> setting in <path>/etc/dnsmasq.conf</path> and restart
the service).
</p>

</body>
</section>

<section>
<title>Connect Another LAN (or two or three or ...)</title>
<body>

<p>
Sometimes you have need of connecting the router to another LAN.  Maybe you 
want to hook up a group of friends temporarily, or you're a neat freak and 
want to section off different groups of computers, or you're just really 
really bored.  Whatever the reasons, extending the router to other LAN 
networks should be pretty straightforward.  In the following examples, I will 
assume that this new network is connected via a third ethernet card, namely 
<c>eth2</c>.
</p>

<p>
First you need to configure the interface.  Just take the instructions in the 
<uri link="#doc_chap4_pre1">4.1 code listing</uri> and replace <c>eth0</c> 
with <c>eth2</c> and <c>192.168.0</c> with <c>192.168.1</c>.
</p>

<p>
Then you need to tweak dnsmasq to service the new interface.  Just edit the 
<path>/etc/conf.d/dnsmasq</path> file again and append <c>-i eth2</c> to 
DNSMASQ_OPTS; using -i multiple times is OK.  Then edit 
<path>/etc/dnsmasq.conf</path> and add another line like the dhcp-range line 
in the <uri link="#doc_chap5_pre1">5.1 code listing</uri>, replacing 
<c>192.168.0</c> with <c>192.168.1</c>.  Having multiple dhcp-range lines is 
OK too.
</p>

<p>
Finally, see the rules in the <uri link="#doc_chap5_pre2">5.2 code 
listing</uri> and duplicate the rules that have <c>-i ${LAN}</c> in them.  You 
may want to create another variable, say <c>LAN2</c>, to make things easier.
</p>

</body>
</section>

</chapter>

<chapter>
<title>Troubleshooting</title>

<section>
<title>Useful Tools</title>
<body>

<p>
If you're having trouble getting your computers to communicate, you may way to 
try out the following tools (they can all be found in the <c>net-analyzer</c> 
portage category):
</p>

<table>
<tr>
  <th>Utility</th>
  <th>Description</th>
</tr>
<tr>
  <ti>ethereal</ti>
  <ti>GUI tool to view all raw network data according to filters</ti>
</tr>
<tr>
  <ti>tcpdump</ti>
  <ti>Console tool to dump all raw network data according to filters</ti>
</tr>
<tr>
  <ti>iptraf</ti>
  <ti>ncurses based IP LAN monitor</ti>
</tr>
<tr>
  <ti>ettercap</ti>
  <ti>ncurses based network monitor/control</ti>
</tr>
</table>

</body>
</section>

<section>
<title>DHCP Fails To Start</title>
<body>

<p>
When starting the dhcp init.d script for the first time, it may fail to load 
but neglect to give you any useful info.
</p>

<pre caption="DHCP Failing Example">
# <i>/etc/init.d/dhcp start</i>
 * Setting ownership on dhcp.leases ...          [ ok ]
 * Starting dhcpd ...                            [ !! ]
</pre>

<p>
The trick is to know where dhcpd is sending its output.  Simply browse to 
/var/log and read the log files.  Since the exact log file depends on the 
package you are using as a syslog, try running <c>grep -Rl dhcpd /var/log</c> 
to narrow down the possibilities.  Chances are you made a typo in your config 
file.  You could also try running <c>dhcpd -d -f</c> (short for debug / 
foreground) and debug the error based upon the output.
</p>

</body>
</section>

<section>
<title>Incorrect MTU Value</title>
<body>

<p>
If you experience odd errors (such as not being some webpages while others 
load fine), you may be having Path MTU Discovery trouble.  The quick way to 
test is to run this iptables command:
</p>

<pre caption="Circumvent MTU issues">
# <i>iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu</i>
</pre>

<p>
This will affect all new connections, so just refresh the website you're 
having problems with in order to test.  In case it helps, the standard MTU 
value for 100mbit ethernet connections is <c>1500</c> while for PPPoE 
connections it is <c>1492</c>.  For more info, you should read Chapter 15 
of the <uri link="http://lartc.org/howto/">Linux Advanced Routing &amp; 
Traffic Control HOWTO</uri>.
</p>

</body>
</section>

</chapter>

<chapter>
<title>Final Notes</title>
<section>
<body>

<p>
I have no final notes other than if you experience any troubles with the guide,
please contact <mail link="vapier@gentoo.org">me</mail> or file a bug with <uri
link="http://bugs.gentoo.org/">Gentoo's Bugtracking Website</uri>.  If you have
some interesting bits you think would enhance this guide, by all means send it
my way for inclusion.
</p>

</body>
</section>
</chapter>
</guide>