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1 <?xml version='1.0' encoding='UTF-8'?>
2 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/home-router-howto.xml,v 1.26 2005/05/25 16:37:15 swift Exp $ -->
3 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
4
5 <guide link="/doc/en/home-router-howto.xml">
6
7 <title>Home Router Guide</title>
8
9 <author title="Author">
10 <mail link="vapier@gentoo.org">Mike Frysinger</mail>
11 </author>
12
13 <abstract>
14 This document details how to turn an old Gentoo machine into a router
15 for connecting your home network to the internet.
16 </abstract>
17
18 <version>1.7</version>
19 <date>2005-06-16</date>
20
21 <chapter>
22 <title>Introduction</title>
23 <section>
24 <body>
25
26 <p>
27 Building your own router out of old spare parts has many advantages over buying
28 a pre-made canned router by say Linksys. The biggest one by far is control
29 over the connection. The other advantages are left up to your imagination;
30 just about anything can be done in this scenario, it's just a matter of needing
31 it.
32 </p>
33
34 <p>
35 This guide will show you how to setup Network Address Translation (NAT) on the
36 router (kernel and iptables), add and configure common services (Domain Name
37 System (DNS) via dnsmasq, dhcp via dhcpcd, ADSL via rp-pppoe), and conclude
38 with more elaborate and fun things that can be done (port forwarding, traffic
39 shaping, proxies/caching, etc...).
40 </p>
41
42 <p>
43 Before getting started, there's a few basic requirements you must meet. First,
44 you'll need a computer that has at least 2 Network Interface Cards (NICs) in
45 it. Next, you'll need the configuration settings for your internet connection
46 (may include things like IP/DNS/Gateway/username/password). Finally, you'll
47 need a bit of spare time and some Gentoo loving.
48 </p>
49
50 <p>
51 The conventions used in this guide are:
52 </p>
53
54 <ul>
55 <li>eth0 - NIC connected to the Local Area Network (LAN)</li>
56 <li>eth1 - NIC connected to the Wide Area Network (WAN)</li>
57 <li>LAN utilizes the private 192.168.0.xxx network</li>
58 <li>router is hardcoded to the standard 192.168.0.1 IP</li>
59 <li>router is running Linux 2.4 or 2.6; you're on your own with 2.0/2.2</li>
60 </ul>
61
62 <impo>
63 Due to security precautions, I would highly suggest you shut down any unneeded
64 services on the router until we have a chance to get the firewall up and
65 rolling. To view the currently running services, just run <c>rc-status</c>.
66 </impo>
67
68 </body>
69 </section>
70 </chapter>
71
72 <chapter>
73 <title>Kernel setup (know thyself first)</title>
74 <section>
75 <body>
76
77 <p>
78 Your kernel needs to have the drivers running for both your NICs. To see if
79 your cards are already setup, just run <c>ifconfig</c>. Your output may differ
80 slightly from the following, that's fine. What matters is that the interface
81 shows up at all.
82 </p>
83
84 <pre caption="Checking NICs">
85 # <i>ifconfig -a</i>
86 eth0 Link encap:Ethernet HWaddr 00:60:F5:07:07:B8
87 BROADCAST MULTICAST MTU:1500 Metric:1
88 RX packets:0 errors:0 dropped:0 overruns:0 frame:0
89 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
90 collisions:0 txqueuelen:1000
91 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
92 Interrupt:11 Base address:0x9800
93
94 eth1 Link encap:Ethernet HWaddr 00:60:F5:07:07:B9
95 BROADCAST MULTICAST MTU:1500 Metric:1
96 RX packets:0 errors:0 dropped:0 overruns:0 frame:0
97 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
98 collisions:0 txqueuelen:1000
99 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
100 Interrupt:10 Base address:0x9400
101 </pre>
102
103 <p>
104 If you do not see your two cards showing up and you're not sure what kind of
105 cards you have, try running <c>lspci</c>. You can get that from <c>emerge
106 pciutils</c>. Look for "Ethernet controller" in the output. Once you have
107 this information, go into your kernel and add support for the correct drivers.
108 </p>
109
110 <p>
111 The next thing you'll need is support for iptables and NAT (and packet shaping
112 if you want). The following list is split up into required (*), suggested (x),
113 and shaper (s) features. It does not matter whether you build the features
114 into the kernel or as a module so long as when the feature is needed, the
115 correct module(s) are loaded (module loading is left to the reader as a fun
116 exercise however).
117 </p>
118
119 <pre caption="Network Options">
120 Networking options ---&gt;
121 [*] TCP/IP networking
122 [*] IP: advanced router
123 [*] Network packet filtering (replaces ipchains)
124 <comment>If you use 2.4.x, you have to enable the following for DHCP:</comment>
125 [*] Socket Filtering
126
127 IP: Netfilter Configuration ---&gt;
128 [*] Connection tracking (required for masq/NAT)
129 [x] FTP protocol support
130 [x] IRC protocol support
131 [*] IP tables support (required for filtering/masq/NAT)
132 [*] IP range match support
133 [x] MAC address match support
134 [*] Multiple port match support
135 [*] Packet filtering
136 [*] REJECT target support
137 [x] REDIRECT target support
138 [*] Full NAT
139 [*] MASQUERADE target support
140 [s] Packet mangling
141 [s] MARK target support
142 [x] LOG target support
143
144 QoS and/or fair queueing ---&gt;
145 [s] QoS and/or fair queueing
146 [s] HTB packet scheduler
147 [s] Ingress Qdisc
148 </pre>
149
150 <note>
151 Somethings may be slightly different in a 2.4 vs 2.6 kernel, but you should be
152 able to figure it out :).
153 </note>
154
155 </body>
156 </section>
157 </chapter>
158
159 <chapter>
160 <title>Hug the WAN (a.k.a. The Internet)</title>
161
162 <section>
163 <title>Intro</title>
164 <body>
165
166 <p>
167 There are many ways to connect to the internet so I'll just cover the ones I'm
168 familiar with. That leaves us with ADSL (PPPoE) and cable modems
169 (static/dynamic). If there are other methods out there, feel free to write up
170 a little blurb and e-mail me. Feel free to skip any of the following sections
171 in this chapter that don't apply to you. This chapter is just about getting
172 the router connected to the internet via eth1.
173 </p>
174
175 </body>
176 </section>
177 <section>
178 <title>ADSL and PPPoE</title>
179 <body>
180
181 <p>
182 All the fancy PPPoE software has been bundled up into one little nice package
183 nowadays called <uri link="http://www.roaringpenguin.com/">Roaring
184 Penguin</uri>. Simply <c>emerge rp-pppoe</c> and you'll be on your way.
185 Remember how I said you'll need username/password information? Well I wasn't
186 lying so I hope you have it now! Load up <path>/etc/ppp/pppoe.conf</path> in
187 your favorite editor and set it up.
188 </p>
189
190 <note>
191 In order for the following net.eth1 settings to work, you must have
192 baselayout-1.10.1 or later installed on your system.
193 </note>
194
195 <pre caption="Setting up eth1">
196 <comment>(Replace 'vla9h924' with your username and 'password' with your password)</comment>
197
198 # <i>nano /etc/ppp/pppoe.conf</i>
199 <comment># Ethernet card connected to ADSL modem</comment>
200 ETH=eth1
201 <comment># ADSL user name.</comment>
202 USER=vla9h924
203 # <i>nano /etc/ppp/pap-secrets</i>
204 <comment># client server secret</comment>
205 "vla9h924" * "password"
206 # <i>nano /etc/conf.d/net</i>
207 <comment>Add an entry for config_eth1 and set it to adsl:</comment>
208 config_eth1=( "adsl" )
209 # <i>ln -s net.eth0 /etc/init.d/net.eth1</i>
210 # <i>rc-update add net.eth1 default</i>
211 # <i>/etc/init.d/net.eth1 start</i>
212 </pre>
213
214 <warn>
215 When the DSL interface comes up, it will create ppp0. Although your NIC
216 is called eth1, the IP is actually bound to ppp0. From now on, when you
217 see examples that utilize 'eth1', substitute with 'ppp0'.
218 </warn>
219
220 </body>
221 </section>
222
223 <section>
224 <title>Cable and/or dynamic/static IP</title>
225 <body>
226
227 <p>
228 If you have a static IP then you will need a few more details than if
229 you have a dynamic IP. For static users, you will need your IP,
230 gateway, and DNS servers.
231 </p>
232
233 <pre caption="Setting up eth1">
234 <comment>Dynamic IP Users:</comment>
235 # <i>emerge dhcpcd</i>
236 # <i>nano /etc/conf.d/net</i>
237 <comment>You'll need an entry like so:</comment>
238 config_eth1=( "dhcp" )
239
240 <comment>Static IP Users:</comment>
241 # <i>nano /etc/conf.d/net</i>
242 <comment>You'll need entries like so:</comment>
243 ifconfig_eth1=( "66.92.78.102 broadcast 66.92.78.255 netmask 255.255.255.0" )
244 routes_eth1=( "default gw 66.92.78.1" )
245 # <i>nano /etc/resolv.conf</i>
246 <comment>Add one line per DNS server:</comment>
247 nameserver 123.123.123.123
248
249 <comment>Dynamic and Static Setup:</comment>
250 # <i>ln -s net.eth0 /etc/init.d/net.eth1</i>
251 # <i>rc-update add net.eth1 default</i>
252 # <i>/etc/init.d/net.eth1 start</i>
253 </pre>
254
255 <p>
256 You should be all set to go now.
257 </p>
258
259 </body>
260 </section>
261 </chapter>
262
263 <chapter>
264 <title>Hug the LAN (bring along some friends)</title>
265 <section>
266 <body>
267
268 <p>
269 This step is a breeze compared to the previous one.
270 </p>
271
272 <pre caption="Setting up eth0">
273 # <i>nano /etc/conf.d/net</i>
274 <comment>Add a line like the following:</comment>
275 ifconfig_eth0=( "192.168.0.1 broadcast 192.168.0.255 netmask 255.255.255.0" )
276 # <i>rc-update add net.eth0 default</i>
277 # <i>/etc/init.d/net.eth0 start</i>
278 </pre>
279
280 </body>
281 </section>
282 </chapter>
283
284 <chapter>
285 <title>LAN Services (because we're nice people)</title>
286
287 <section>
288 <title>DHCP Server</title>
289 <body>
290
291 <p>
292 I bet it'd be nice if everyone else in your house could just plug their
293 computers into the network and things would just work. No need to remember
294 mind-numbing details or make them stare at confusing configuration screens!
295 Life would be grand eh? Introducing the Dynamic Host Configuration Protocol
296 (DHCP) and why you should care.
297 </p>
298
299 <p>
300 DHCP is exactly what its name implies. It's a protocol that allows you
301 to dynamically configure other hosts automatically. You run a DHCP server on
302 the router (dhcpd), give it all the information about your network (valid IPs,
303 DNS servers, gateways, etc...), and then when the other hosts start up, they
304 run a DHCP client to automatically configure themselves. No fuss, no muss!
305 For more information about DHCP, you can always visit <uri
306 link="http://en.wikipedia.org/wiki/DHCP">Wikipedia</uri>.
307 </p>
308
309 <pre caption="Setting up dhcpd">
310 # <i>emerge dhcp</i>
311 # <i>nano /etc/dhcp/dhcpd.conf</i>
312 <comment>(Here is a sample configuration file:)</comment>
313 authoritative;
314 ddns-update-style interim;
315 subnet 192.168.0.0 netmask 255.255.255.0 {
316 range 192.168.0.100 192.168.0.250;
317 default-lease-time 259200;
318 max-lease-time 518400;
319 option subnet-mask 255.255.255.0;
320 option broadcast-address 192.168.0.255;
321 option routers 192.168.0.1;
322 option domain-name-servers 192.168.0.1;
323 }
324 # <i>nano /etc/conf.d/dhcp</i>
325 <comment>(Set IFACE="eth0")</comment>
326 # <i>rc-update add dhcp default</i>
327 # <i>/etc/init.d/dhcp start</i>
328 </pre>
329
330 <p>
331 Now your little router is a bona-fide DHCP server! Plugin those computers and
332 watch them work! With Windows systems you should go into the TCP/IP Properties
333 and select the 'Obtain an IP address automatically' and 'Obtain DNS server
334 address automatically' options. Sometimes the changes aren't instantaneous, so
335 you may have to run a command prompt and run <c>ipconfig /release</c> and
336 <c>ipconfig /renew</c>. But enough about Windows, let's get back to our
337 favorite penguin.
338 </p>
339
340 </body>
341 </section>
342
343 <section>
344 <title>DNS Server</title>
345 <body>
346
347 <p>
348 When people want to visit a place on the internet, they remember names, not a
349 string of useless numbers. After all, what's easier to remember, ebay.com or
350 66.135.192.87? This is where the DNS steps in. DNS servers run all over the
351 internet, and whenever someone wants to visit 'ebay.com', these servers turn
352 'ebay.com' (what we understand) into '66.135.192.87' (what our computers
353 understand). For more information about DNS, you can always visit <uri
354 link="http://en.wikipedia.org/wiki/DNS">Wikipedia</uri>.
355 </p>
356
357 <p>
358 You may have noticed in the previous section that we told the DHCP clients we
359 have a DNS server at 192.168.0.1. You may also remember that 192.168.0.1 is
360 our little router that we're making. I don't remember setting up a DNS server
361 ... so let's do so now!
362 </p>
363
364 <pre caption="Setting up dnsmasq">
365 # <i>emerge dnsmasq</i>
366 # <i>nano /etc/conf.d/dnsmasq</i>
367 <comment>Add "-i eth0" to DNSMASQ_OPTS</comment>
368 # <i>rc-update add dnsmasq default</i>
369 # <i>/etc/init.d/dnsmasq start</i>
370 </pre>
371
372 <p>
373 Well that was quick, but what did we do? The great thing is, we didn't have to
374 do very much! You're welcome to choose other DNS servers if you're more
375 comfortable with them, but the reason dnsmasq is great is because it was
376 designed to do exactly what we want and nothing more. It's a little DNS
377 caching/forwarding server for local networks. We're not looking to provide DNS
378 for our own domain here, just offer simple DNS services to everyone else on our
379 LAN.
380 </p>
381
382 </body>
383 </section>
384
385 <section>
386 <title>NAT (a.k.a. IP-masquerading)</title>
387 <body>
388
389 <p>
390 At this point, people on your network can talk to each other and they can look
391 up hostnames via DNS, but they still can't actually connect to the internet.
392 While you may think that's great (more bandwidth for you!), I bet they're not
393 too happy just yet.
394 </p>
395
396 <p>
397 This is where NAT steps in. NAT is a way of connecting multiple computers in a
398 private LAN to the internet when you only have a smaller number of IP addresses
399 availabe to you. Typically you were given 1 IP by your ISP, but you want to
400 let your whole house connect to the internet. NAT is the magic that makes this
401 possible. For more information about NAT, you can always visit <uri
402 link="http://en.wikipedia.org/wiki/NAT">Wikipedia</uri>.
403 </p>
404
405 <note>
406 Before we get started, make sure you have iptables on your system. Although it
407 is automatically installed on most systems, you may not have it. If you don't,
408 just run <c>emerge iptables</c>.
409 </note>
410
411 <pre caption="Setting up iptables">
412 <comment>First we flush our current rules</comment>
413 # <i>iptables -F</i>
414 # <i>iptables -t nat -F</i>
415
416 <comment>Then we lock our services so they only work from the LAN</comment>
417 # <i>iptables -I INPUT 1 -i eth0 -j ACCEPT</i>
418 # <i>iptables -I INPUT 1 -i lo -j ACCEPT</i>
419 # <i>iptables -A INPUT -p UDP --dport bootps -i ! eth0 -j REJECT</i>
420 # <i>iptables -A INPUT -p UDP --dport domain -i ! eth0 -j REJECT</i>
421
422 <comment>(Optional) Allow access to our ssh server from the WAN</comment>
423 # <i>iptables -A INPUT -p TCP --dport ssh -i eth1 -j ACCEPT</i>
424
425 <comment>Drop TCP / UDP packets to privileged ports</comment>
426 # <i>iptables -A INPUT -p TCP -i ! eth0 -d 0/0 --dport 0:1023 -j DROP</i>
427 # <i>iptables -A INPUT -p UDP -i ! eth0 -d 0/0 --dport 0:1023 -j DROP</i>
428
429 <comment>Finally we add the rules for NAT</comment>
430 # <i>iptables -I FORWARD -i eth0 -d 192.168.0.0/255.255.0.0 -j DROP</i>
431 # <i>iptables -A FORWARD -i eth0 -s 192.168.0.0/255.255.0.0 -j ACCEPT</i>
432 # <i>iptables -A FORWARD -i eth1 -d 192.168.0.0/255.255.0.0 -j ACCEPT</i>
433 # <i>iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE</i>
434 <comment>Tell the kernel that ip forwarding is OK</comment>
435 # <i>echo 1 > /proc/sys/net/ipv4/ip_forward</i>
436 # <i>for f in /proc/sys/net/ipv4/conf/*/rp_filter ; do echo 1 > $f ; done</i>
437
438 <comment>This is so when we boot we don't have to run the rules by hand</comment>
439 # <i>/etc/init.d/iptables save</i>
440 # <i>rc-update add iptables default</i>
441 # <i>nano /etc/sysctl.conf</i>
442 <comment>Add/Uncomment the following lines:
443 net.ipv4.ip_forward = 1
444 net.ipv4.conf.default.rp_filter = 1</comment>
445 </pre>
446
447 <p>
448 Once you've typed out all of that, the rest of your network should now be able
449 to use the internet as if they were directly connected themselves.
450 </p>
451
452 </body>
453 </section>
454 </chapter>
455
456 <chapter>
457 <title>Fun Things (for a rainy day)</title>
458
459 <section>
460 <title>Intro</title>
461 <body>
462
463 <p>
464 Believe it or not, you're done :). From here on out, I'll cover a bunch of
465 common topics that may interest you. Everything in this chapter is completely
466 optional.
467 </p>
468
469 </body>
470 </section>
471
472 <section>
473 <title>Port Forwarding</title>
474 <body>
475
476 <p>
477 Sometimes you would like to be able to host services on a computer behind the
478 router, or just to make your life easier when connecting remotely. Perhaps you
479 want to run a FTP, HTTP, SSH, or VNC server on one or more machines behind your
480 router and be able to connect to them all. The only caveat is that you can
481 only have one service/machine combo per port. For example, there is no
482 practical way to setup three FTP servers behind your router and then try to
483 connect to them all through port 21; only one can be on port 21 while the
484 others would have to be on say port 123 and port 567.
485 </p>
486
487 <p>
488 All the port forwarding rules are of the form <c>iptables -t nat -A PREROUTING
489 [-p protocol] --dport [external port on router] -i eth1 -j DNAT --to [ip/port
490 to forward to]</c>. iptables does not accept hostnames when port forwarding.
491 If you are forwarding an external port to the same port on the internal
492 machine, you can omit the destination port. See the iptables(8) page for more
493 information.
494 </p>
495
496 <pre>
497 <comment>Forward port 2 to ssh on an internal host</comment>
498 # <i>iptables -t nat -A PREROUTING -p tcp --dport 2 -i eth1 -j DNAT --to 192.168.0.2:22</i>
499
500 <comment>FTP forwarding to an internal host</comment>
501 # <i>iptables -t nat -A PREROUTING -p tcp --dport 21 -i eth1 -j DNAT --to 192.168.0.56</i>
502
503 <comment>HTTP forwarding to an internal host</comment>
504 # <i>iptables -t nat -A PREROUTING -p tcp --dport 80 -i eth1 -j DNAT --to 192.168.0.56</i>
505
506 <comment>VNC forwarding for internal hosts</comment>
507 # <i>iptables -t nat -I PREROUTING -p tcp --dport 5900 -i eth1 -j DNAT --to 192.168.0.2</i>
508 # <i>iptables -t nat -I PREROUTING -p tcp --dport 5901 -i eth1 -j DNAT --to 192.168.0.3:5900</i>
509 <comment>If you want to VNC in to 192.168.0.3, then just add ':1' to the router's hostname</comment>
510
511 <comment>Bittorrent forwarding</comment>
512 # <i>iptables -t nat -A PREROUTING -p tcp --dport 6881:6889 -i eth1 -j DNAT --to 192.168.0.2</i>
513
514 <comment>Game Cube Warp Pipe support</comment>
515 # <i>iptables -t nat -A PREROUTING -p udp --dport 4000 -i eth1 -j DNAT --to 192.168.0.56</i>
516
517 <comment>Playstation2 Online support</comment>
518 # <i>iptables -t nat -A PREROUTING -p tcp --dport 10070:10080 -i eth1 -j DNAT --to 192.168.0.11</i>
519 # <i>iptables -t nat -A PREROUTING -p udp --dport 10070:10080 -i eth1 -j DNAT --to 192.168.0.11</i>
520 </pre>
521
522 <note>
523 If you have other common / cool examples, please <uri
524 link="mailto:vapier@gentoo.org">e-mail me</uri>.
525 </note>
526
527 </body>
528 </section>
529
530 <section>
531 <title>Identd (for IRC)</title>
532 <body>
533
534 <p>
535 Internet Relay Chat utilizes the ident service pretty heavily. Now that the
536 IRC clients are behind the router, we need a way to host ident for both the
537 router and the clients. One such server has been created called
538 <c>midentd</c>.
539 </p>
540
541 <pre caption="Setting up ident">
542 # <i>emerge midentd</i>
543 # <i>rc-update add midentd default</i>
544 # <i>/etc/init.d/midentd start</i>
545 </pre>
546
547 <p>
548 There are a few other ident servers in portage. Depending on your needs, I
549 would recommend checking out <c>oidentd</c> and <c>fakeidentd</c>.
550 </p>
551
552 </body>
553 </section>
554
555 <!--
556 <section>
557 <title>Traffic Shaping</title>
558 <body>
559 <p>
560 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>
561 found over at the TLDP. Feel free to refer to the original document
562 for more details.
563 </p>
564
565 <p>
566 Here we will be setting up what some people refer to as a "Packet Shaper",
567 <uri link="http://en.wikipedia.org/wiki/Traffic_shaping">"Traffic Shaping"</uri>,
568 or <uri link="http://en.wikipedia.org/wiki/QoS">"Quality of Service"</uri>.
569 Simply put, we want to setup rules on our router that will slow down
570 certain activities (like sending large e-mails or downloading from P2P
571 networks) while keeping other activities (like browsing the web or playing
572 online video games) reasonably fast. A 30 second difference in a video
573 game is a lot worse than a 30 second difference in downloading large
574 files :).
575 </p>
576
577 <p>
578 The first thing is to make sure your kernel has all the features added to
579 it. See the chapter on <uri link="#doc_chap2">Kernel setup</uri> for more
580 information. Next, you will need to <c>emerge iptables iputils</c> so that
581 you will have access to the <c>iptables</c>, <c>ip</c>, and <c>tc</c>
582 commands.
583 </p>
584
585 <p>
586 Before we jump into the commands, let's cover a little of the theory. The
587 way this whole system works is to classify common network streams and then
588 to prioritize them. You use iptables to classify network streams, iputils
589 to define the different priority levels, and the kernel to adjust speeds.
590 Just remember that although you can control outbound traffic pretty tightly
591 (from the LAN to the WAN), your ability to control inbound traffic (from
592 the WAN to the LAN) is somewhat limited. Just remember that the following
593 examples are to get your feet wet; if you want more then I'd suggest
594 reading up on the subject. In this example, we will be using the
595 <uri link="http://luxik.cdi.cz/~devik/qos/htb/">Hierarchical Token Buckets (HTB)</uri>
596 packet scheduling algorithm. Still with me? Great, let's start shaping :).
597 </p>
598
599 <pre caption="Setup">
600 DEV=eth1 <comment>NIC connected to WAN</comment>
601 RATE_OUT=100 <comment>Available outbound bandwidth (in kilobits [kb])</comment>
602 RATE_IN=1400 <comment>Available inbound bandwidth (in kb)</comment>
603
604 <comment>Here we initialize the priority system. The 45 is used to set the default classification level.</comment>
605 ip link set dev ${DEV} qlen 30
606 tc qdisc add dev ${DEV} root handle 1: htb default 45
607 tc class add dev ${DEV} parent 1: classid 1:1 htb rate ${RATE_OUT}kbit
608 </pre>
609
610 <p>
611 Here we initialized the system which will be used to prioritize all of
612 our network traffic. We created our queue, told it to use the HTB
613 algorithm, and set the default classification level to '45'. The
614 default is completely arbitrary, as are the levels we choose from
615 here on out. The only thing that matters is how the levels compare
616 relatively; a level '10' packet will be given preference over a
617 level '45' packet. Let's move on to declaring different levels.
618 </p>
619
620 <pre caption="Declaring levels">
621 tc class add dev $DEV parent 1:1 classid 1:10 htb rate $rkbit ceil $tkbit prio $p
622 tc qdisc add dev $DEV parent 1:10 handle 10: sfq
623 </pre>
624 </body>
625 </section>
626 -->
627
628 <section>
629 <title>Time Server</title>
630 <body>
631
632 <p>
633 Keeping your system time correct is essential in maintaining a healthy system.
634 One of the most common ways of accomplishing this is with the Network Time
635 Protocol (NTP) and the ntp package (which provides implementations for both
636 server and client).
637 </p>
638
639 <p>
640 Many people run ntp clients on their computers. Obviously, the more clients in
641 the world, the larger the load the ntp servers need to shoulder. In
642 environments like home networks though, we can help keep the load down on
643 public servers while still providing the proper time to all our computers. As
644 an added bonus, our private updates will be a lot faster for the clients too!
645 All we have to do is run a ntp server on our router that synchronizes itself
646 with the public internet servers while providing the time to the rest of the
647 computers in the network. To get started, simply <c>emerge ntp</c> on the
648 router.
649 </p>
650
651 <pre caption="Setting up the NTP server">
652 # <i>nano /etc/conf.d/ntp-client</i>
653 <comment>Customize if you wish but the defaults should be fine</comment>
654 # <i>rc-update add ntp-client default</i>
655
656 # <i>nano /etc/ntp.conf</i>
657 <comment>Add the follwing lines:</comment>
658 restrict default ignore
659 restrict 192.168.0.0 mask 255.255.255.0 notrust nomodify notrap
660 <comment>These will allow only ntp clients with an IP
661 address in the 192.168.0.xxx range to use your ntp server</comment>
662 # <i>nano /etc/conf.d/ntpd</i>
663 <comment>Customize if you wish but the defaults should be fine</comment>
664 # <i>rc-update add ntpd default</i>
665
666 # <i>/etc/init.d/ntp-client start</i>
667 # <i>/etc/init.d/ntpd start</i>
668 </pre>
669
670 <note>
671 You should make sure that you allow inbound and outbound communication on the
672 ntp port (123/udp) when setting up the server. The client just needs outbound
673 access on port 123 over udp.
674 </note>
675
676 <p>
677 Now, on your clients, have them <c>emerge ntp</c> also. However, we will just
678 run the ntp client so setup is a lot simpler.
679 </p>
680
681 <pre caption="Setting up a NTP client">
682 # <i>nano /etc/conf.d/ntp-client</i>
683 <comment>Change the 'pool.ntp.org' server in the NTPCLIENT_OPTS variable to '192.168.0.1'</comment>
684 # <i>rc-update add ntp-client default</i>
685 # <i>/etc/init.d/ntp-client start</i>
686 </pre>
687
688 </body>
689 </section>
690
691 <section>
692 <title>Mail Server</title>
693 <body>
694
695 <p>
696 Sometimes it's nice to run your own Simple Mail Transfer Protocol (SMTP) server
697 on the router. You may have your own reason for wanting to do so, but I run it
698 so that the users see mail as being sent instantly and the work of
699 retrying/routing is left up to the mail server. Some ISPs also don't allow for
700 mail relaying for accounts that aren't part of their network (like Verizon).
701 Also, you can easily throttle the delivery of mail so that large attachments
702 won't seriously lag your connection for half an hour.
703 </p>
704
705 <pre caption="Setting up SMTP">
706 # <i>emerge qmail</i>
707 <comment>make sure the output of `hostname` is correct</comment>
708 # <i>ebuild /var/db/pkg/*-*/qmail-1.03-r*/*.ebuild config</i>
709 # <i>iptables -I INPUT -p tcp --dport smtp -i ! eth0 -j REJECT</i>
710 # <i>ln -s /var/qmail/supervise/qmail-send /service/qmail-send</i>
711 # <i>ln -s /var/qmail/supervise/qmail-smtpd /service/qmail-smtpd</i>
712 <!--
713 # <i>cd /etc/tcprules.d</i>
714 # <i>nano tcp.qmail-smtp</i>
715 -->
716 # <i>cd /etc</i>
717 # <i>nano tcp.smtp</i>
718 <comment>Add an entry like so to the allow section:</comment>
719 192.168.0.:allow,RELAYCLIENT=""
720 <!--
721 # <i>tcprules tcp.qmail-qmtp.cdb rules.tmp &lt; tcp.qmail-smtp</i>
722 -->
723 # <i>tcprules tcp.smtp.cdb rules.tmp &lt; tcp.smtp</i>
724 # <i>rc-update add svscan default</i>
725 # <i>/etc/init.d/svscan start</i>
726 </pre>
727
728 <p>
729 I'm a huge fan of qmail, but you're free to use a different mta :). When you
730 setup e-mail on the hosts in your network, tell them that their SMTP server is
731 192.168.0.1 and everything should be peachy. You might want to visit the <uri
732 link="http://qmail.org/">qmail homepage</uri> for more documentation.
733 </p>
734
735 </body>
736 </section>
737
738 <!--
739 <section>
740 <title>E-mail Virus Scanning</title>
741 <body>
742 <p>
743 If you'd like to provide e-mail virus scanning for your users, but
744 don't want to have to install a virus scanner on every single machine,
745 then <c>pop3vscan</c> may just be the thing for you; a transparent
746 Post Office Protocol (POP) scanner.
747 </p>
748
749 <pre caption="Setting up pop3vscan">
750 TODO
751 </pre>
752
753 </body>
754 </section>
755 -->
756
757 </chapter>
758
759 <chapter>
760 <title>Debugging</title>
761
762 <section>
763 <title>Useful Tools</title>
764 <body>
765
766 <p>
767 If you're having trouble getting your computers to communicate, you may way to
768 try out the following tools (they can all be found in the <c>net-analyzer</c>
769 portage category):
770 </p>
771
772 <table>
773 <tr>
774 <th>Utility</th>
775 <th>Description</th>
776 </tr>
777 <tr>
778 <ti>ethereal</ti>
779 <ti>GUI tool to view all raw network data according to filters</ti>
780 </tr>
781 <tr>
782 <ti>tcpdump</ti>
783 <ti>Console tool to dump all raw network data according to filters</ti>
784 </tr>
785 <tr>
786 <ti>iptraf</ti>
787 <ti>ncurses based IP LAN monitor</ti>
788 </tr>
789 <tr>
790 <ti>ettercap</ti>
791 <ti>ncurses based network monitor/control</ti>
792 </tr>
793 </table>
794
795 </body>
796 </section>
797
798 <section>
799 <title>Incorrect MTU Value</title>
800 <body>
801
802 <p>
803 If you experience odd errors (such as not being some webpages while others
804 load fine), you may be having Path MTU Discovery trouble. The quick way to
805 test is to run this iptables command:
806 </p>
807
808 <pre caption="Circumvent MTU issues">
809 # <i>iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu</i>
810 </pre>
811
812 <p>
813 This will affect all new connections, so just refresh the website you're
814 having problems with in order to test. In case it helps, the standard MTU
815 value for 100mbit ethernet connections is <c>1500</c> while for PPPoE
816 connections it is <c>1492</c>. For more info, you should read Chapter 15
817 of the <uri link="http://lartc.org/howto/">Linux Advanced Routing &amp;
818 Traffic Control HOWTO</uri>.
819 </p>
820
821 </body>
822 </section>
823
824 </chapter>
825
826 <chapter>
827 <title>Final Notes</title>
828 <section>
829 <body>
830
831 <p>
832 I have no final notes other than if you experience any troubles with the guide,
833 please contact <mail link="vapier@gentoo.org">me</mail> or file a bug with <uri
834 link="http://bugs.gentoo.org/">Gentoo's Bugtracking Website</uri>. If you have
835 some interesting bits you think would enhance this guide, by all means send it
836 my way for inclusion.
837 </p>
838
839 </body>
840 </section>
841 </chapter>
842 </guide>

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