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Revision 1.33 - (show annotations) (download) (as text)
Sat Sep 17 07:40:13 2005 UTC (9 years ago) by vapier
Branch: MAIN
Changes since 1.32: +90 -55 lines
File MIME type: application/xml
replace the dhcp section with the dhcp server from dnsmasq as suggested by many peeps, move the old dhcp section to the Fun section, touchup grammer in a few sections, and add an example iptables rule for edonkey

1 <?xml version='1.0' encoding='UTF-8'?>
2 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/home-router-howto.xml,v 1.32 2005/09/06 03:03:19 vapier 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>1.20</version>
19 <date>2005-09-17</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.lo /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.lo /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, 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 <p>
310 We'll use a package called dnsmasq which provides both DHCP and DNS services.
311 For now lets just focus on the DHCP aspect. Note that if you want to run a
312 different DHCP server, you can find another example in the Fun Things chapter.
313 Also, if you wish to tinker with the DHCP server settings, just read the
314 comments in <path>/etc/dnsmasq.conf</path>. All the defaults should work fine
315 though.
316 </p>
317
318 <pre caption="Setting up a DHCP server">
319 # <i>emerge dnsmasq</i>
320 # <i>nano /etc/dnsmasq.conf</i>
321 <comment>You should need to just add this one line:</comment>
322 dhcp-range=192.168.0.100,192.168.0.250,72h
323
324 # <i>nano /etc/conf.d/dnsmasq</i>
325 <comment>Add "-i eth0" to DNSMASQ_OPTS</comment>
326 # <i>rc-update add dnsmasq default</i>
327 # <i>/etc/init.d/dnsmasq 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 open 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 funky 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 Since we're using dnsmasq for our DHCP server, and it includes a DNS server,
359 you've got nothing left to do here! Your little router is already providing
360 DNS to its DHCP clients. Bet you wish everything was this easy ;).
361 </p>
362
363 <p>
364 You're welcome to choose other DNS servers if you're more comfortable with
365 them, but the reason dnsmasq is great is because it was designed to do exactly
366 what we want and nothing more. It's a little DNS caching/forwarding server for
367 local networks. We're not looking to provide DNS for our own domain here, just
368 offer simple DNS services to everyone else on our LAN.
369 </p>
370
371 </body>
372 </section>
373
374 <section>
375 <title>NAT (a.k.a. IP-masquerading)</title>
376 <body>
377
378 <p>
379 At this point, people on your network can talk to each other and they can look
380 up hostnames via DNS, but they still can't actually connect to the internet.
381 While you may think that's great (more bandwidth for you!), I bet they're not
382 too happy just yet.
383 </p>
384
385 <p>
386 This is where Network Address Translation (NAT) steps in. NAT is a way of
387 connecting multiple computers in a private LAN to the internet when you have a
388 smaller number of public IP addresses available to you. Typically you are given
389 1 IP by your ISP, but you want to let your whole house connect to the internet.
390 NAT is the magic that makes this possible. For more information about NAT, you
391 can always visit <uri link="http://en.wikipedia.org/wiki/NAT">Wikipedia</uri>.
392 </p>
393
394 <note>
395 Before we get started, make sure you have iptables on your system. Although it
396 is automatically installed on most systems, you may not have it. If you don't,
397 just run <c>emerge iptables</c>.
398 </note>
399
400 <pre caption="Setting up iptables">
401 <comment>First we flush our current rules</comment>
402 # <i>iptables -F</i>
403 # <i>iptables -t nat -F</i>
404
405 <comment>Setup default policies to handle unmatched traffic</comment>
406 # <i>iptables -P INPUT ACCEPT</i>
407 # <i>iptables -P OUTPUT ACCEPT</i>
408 # <i>iptables -P FORWARD DROP</i>
409
410 <comment>Copy and paste these examples ...</comment>
411 # <i>export LAN=eth0</i>
412 # <i>export WAN=eth1</i>
413
414 <comment>Then we lock our services so they only work from the LAN</comment>
415 # <i>iptables -I INPUT 1 -i ${LAN} -j ACCEPT</i>
416 # <i>iptables -I INPUT 1 -i lo -j ACCEPT</i>
417 # <i>iptables -A INPUT -p UDP --dport bootps -i ! ${LAN} -j REJECT</i>
418 # <i>iptables -A INPUT -p UDP --dport domain -i ! ${LAN} -j REJECT</i>
419
420 <comment>(Optional) Allow access to our ssh server from the WAN</comment>
421 # <i>iptables -A INPUT -p TCP --dport ssh -i ${WAN} -j ACCEPT</i>
422
423 <comment>Drop TCP / UDP packets to privileged ports</comment>
424 # <i>iptables -A INPUT -p TCP -i ! ${LAN} -d 0/0 --dport 0:1023 -j DROP</i>
425 # <i>iptables -A INPUT -p UDP -i ! ${LAN} -d 0/0 --dport 0:1023 -j DROP</i>
426
427 <comment>Finally we add the rules for NAT</comment>
428 # <i>iptables -I FORWARD -i ${LAN} -d 192.168.0.0/255.255.0.0 -j DROP</i>
429 # <i>iptables -A FORWARD -i ${LAN} -s 192.168.0.0/255.255.0.0 -j ACCEPT</i>
430 # <i>iptables -A FORWARD -i ${WAN} -d 192.168.0.0/255.255.0.0 -j ACCEPT</i>
431 # <i>iptables -t nat -A POSTROUTING -o ${WAN} -j MASQUERADE</i>
432 <comment>Tell the kernel that ip forwarding is OK</comment>
433 # <i>echo 1 > /proc/sys/net/ipv4/ip_forward</i>
434 # <i>for f in /proc/sys/net/ipv4/conf/*/rp_filter ; do echo 1 > $f ; done</i>
435
436 <comment>This is so when we boot we don't have to run the rules by hand</comment>
437 # <i>/etc/init.d/iptables save</i>
438 # <i>rc-update add iptables default</i>
439 # <i>nano /etc/sysctl.conf</i>
440 <comment>Add/Uncomment the following lines:
441 net.ipv4.ip_forward = 1
442 net.ipv4.conf.default.rp_filter = 1</comment>
443 </pre>
444
445 <p>
446 Once you've typed out all of that, the rest of your network should now be able
447 to use the internet as if they were directly connected themselves.
448 </p>
449
450 </body>
451 </section>
452 </chapter>
453
454 <chapter>
455 <title>Fun Things (for a rainy day)</title>
456
457 <section>
458 <title>Intro</title>
459 <body>
460
461 <p>
462 Believe it or not, you're done :). From here on out, I'll cover a bunch of
463 common topics that may interest you. Everything in this chapter is completely
464 optional.
465 </p>
466
467 </body>
468 </section>
469
470 <section>
471 <title>Port Forwarding</title>
472 <body>
473
474 <p>
475 Sometimes you would like to be able to host services on a computer behind the
476 router, or just to make your life easier when connecting remotely. Perhaps you
477 want to run a FTP, HTTP, SSH, or VNC server on one or more machines behind your
478 router and be able to connect to them all. The only caveat is that you can
479 only have one service/machine combo per port. For example, there is no
480 practical way to setup three FTP servers behind your router and then try to
481 connect to them all through port 21; only one can be on port 21 while the
482 others would have to be on say port 123 and port 567.
483 </p>
484
485 <p>
486 All the port forwarding rules are of the form <c>iptables -t nat -A PREROUTING
487 [-p protocol] --dport [external port on router] -i ${WAN} -j DNAT --to [ip/port
488 to forward to]</c>. Unfortunately, iptables does not accept hostnames when port
489 forwarding. If you are forwarding an external port to the same port on the
490 internal machine, you can omit the destination port. See the iptables(8) man
491 page for more information.
492 </p>
493
494 <pre caption="Running the iptables commands">
495 <comment>Copy and paste these examples ...</comment>
496 # <i>export LAN=eth0</i>
497 # <i>export WAN=eth1</i>
498
499 <comment>Forward port 2 to ssh on an internal host</comment>
500 # <i>iptables -t nat -A PREROUTING -p tcp --dport 2 -i ${WAN} -j DNAT --to 192.168.0.2:22</i>
501
502 <comment>FTP forwarding to an internal host</comment>
503 # <i>iptables -t nat -A PREROUTING -p tcp --dport 21 -i ${WAN} -j DNAT --to 192.168.0.56</i>
504
505 <comment>HTTP forwarding to an internal host</comment>
506 # <i>iptables -t nat -A PREROUTING -p tcp --dport 80 -i ${WAN} -j DNAT --to 192.168.0.56</i>
507
508 <comment>VNC forwarding for internal hosts</comment>
509 # <i>iptables -t nat -I PREROUTING -p tcp --dport 5900 -i ${WAN} -j DNAT --to 192.168.0.2</i>
510 # <i>iptables -t nat -I PREROUTING -p tcp --dport 5901 -i ${WAN} -j DNAT --to 192.168.0.3:5900</i>
511 <comment>If you want to VNC in to 192.168.0.3, then just add ':1' to the router's hostname</comment>
512
513 <comment>Bittorrent forwarding</comment>
514 # <i>iptables -t nat -A PREROUTING -p tcp --dport 6881:6889 -i ${WAN} -j DNAT --to 192.168.0.2</i>
515
516 <comment>eDonkey/eMule forwarding</comment>
517 # <i>iptables -t nat -A PREROUTING -p tcp --dport 4662 -i ${WAN} -j DNAT --to 192.168.0.55</i>
518
519 <comment>Game Cube Warp Pipe support</comment>
520 # <i>iptables -t nat -A PREROUTING -p udp --dport 4000 -i ${WAN} -j DNAT --to 192.168.0.56</i>
521
522 <comment>Playstation 2 Online support</comment>
523 # <i>iptables -t nat -A PREROUTING -p tcp --dport 10070:10080 -i ${WAN} -j DNAT --to 192.168.0.11</i>
524 # <i>iptables -t nat -A PREROUTING -p udp --dport 10070:10080 -i ${WAN} -j DNAT --to 192.168.0.11</i>
525 </pre>
526
527 <note>
528 If you have other common / cool examples, please <uri
529 link="mailto:vapier@gentoo.org">e-mail me</uri>.
530 </note>
531
532 </body>
533 </section>
534
535 <section>
536 <title>Identd (for IRC)</title>
537 <body>
538
539 <p>
540 Internet Relay Chat utilizes the ident service pretty heavily. Now that the
541 IRC clients are behind the router, we need a way to host ident for both the
542 router and the clients. One such server has been created called
543 <c>midentd</c>.
544 </p>
545
546 <pre caption="Setting up ident">
547 # <i>emerge midentd</i>
548 # <i>rc-update add midentd default</i>
549 # <i>/etc/init.d/midentd start</i>
550 </pre>
551
552 <p>
553 There are a few other ident servers in portage. Depending on your needs, I
554 would recommend checking out <c>oidentd</c> and <c>fakeidentd</c>.
555 </p>
556
557 </body>
558 </section>
559
560 <!--
561 <section>
562 <title>Traffic Shaping</title>
563 <body>
564 <p>
565 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>
566 found over at the TLDP. Feel free to refer to the original document
567 for more details.
568 </p>
569
570 <p>
571 Here we will be setting up what some people refer to as a "Packet Shaper",
572 <uri link="http://en.wikipedia.org/wiki/Traffic_shaping">"Traffic Shaping"</uri>,
573 or <uri link="http://en.wikipedia.org/wiki/QoS">"Quality of Service"</uri>.
574 Simply put, we want to setup rules on our router that will slow down
575 certain activities (like sending large e-mails or downloading from P2P
576 networks) while keeping other activities (like browsing the web or playing
577 online video games) reasonably fast. A 30 second difference in a video
578 game is a lot worse than a 30 second difference in downloading large
579 files :).
580 </p>
581
582 <p>
583 The first thing is to make sure your kernel has all the features added to
584 it. See the chapter on <uri link="#doc_chap2">Kernel setup</uri> for more
585 information. Next, you will need to <c>emerge iptables iputils</c> so that
586 you will have access to the <c>iptables</c>, <c>ip</c>, and <c>tc</c>
587 commands.
588 </p>
589
590 <p>
591 Before we jump into the commands, let's cover a little of the theory. The
592 way this whole system works is to classify common network streams and then
593 to prioritize them. You use iptables to classify network streams, iputils
594 to define the different priority levels, and the kernel to adjust speeds.
595 Just remember that although you can control outbound traffic pretty tightly
596 (from the LAN to the WAN), your ability to control inbound traffic (from
597 the WAN to the LAN) is somewhat limited. Just remember that the following
598 examples are to get your feet wet; if you want more then I'd suggest
599 reading up on the subject. In this example, we will be using the
600 <uri link="http://luxik.cdi.cz/~devik/qos/htb/">Hierarchical Token Buckets (HTB)</uri>
601 packet scheduling algorithm. Still with me? Great, let's start shaping :).
602 </p>
603
604 <pre caption="Setup">
605 DEV=eth1 <comment>NIC connected to WAN</comment>
606 RATE_OUT=100 <comment>Available outbound bandwidth (in kilobits [kb])</comment>
607 RATE_IN=1400 <comment>Available inbound bandwidth (in kb)</comment>
608
609 <comment>Here we initialize the priority system. The 45 is used to set the default classification level.</comment>
610 ip link set dev ${DEV} qlen 30
611 tc qdisc add dev ${DEV} root handle 1: htb default 45
612 tc class add dev ${DEV} parent 1: classid 1:1 htb rate ${RATE_OUT}kbit
613 </pre>
614
615 <p>
616 Here we initialized the system which will be used to prioritize all of
617 our network traffic. We created our queue, told it to use the HTB
618 algorithm, and set the default classification level to '45'. The
619 default is completely arbitrary, as are the levels we choose from
620 here on out. The only thing that matters is how the levels compare
621 relatively; a level '10' packet will be given preference over a
622 level '45' packet. Let's move on to declaring different levels.
623 </p>
624
625 <pre caption="Declaring levels">
626 tc class add dev $DEV parent 1:1 classid 1:10 htb rate $rkbit ceil $tkbit prio $p
627 tc qdisc add dev $DEV parent 1:10 handle 10: sfq
628 </pre>
629 </body>
630 </section>
631 -->
632
633 <section>
634 <title>Time Server</title>
635 <body>
636
637 <p>
638 Keeping your system time correct is essential in maintaining a healthy system.
639 One of the most common ways of accomplishing this is with the Network Time
640 Protocol (NTP) and the ntp package (which provides implementations for both
641 server and client).
642 </p>
643
644 <p>
645 Many people run ntp clients on their computers. Obviously, the more clients in
646 the world, the larger the load the ntp servers need to shoulder. In
647 environments like home networks though, we can help keep the load down on
648 public servers while still providing the proper time to all our computers. As
649 an added bonus, our private updates will be a lot faster for the clients too!
650 All we have to do is run a ntp server on our router that synchronizes itself
651 with the public internet servers while providing the time to the rest of the
652 computers in the network. To get started, simply <c>emerge ntp</c> on the
653 router.
654 </p>
655
656 <pre caption="Setting up the NTP server">
657 # <i>nano /etc/conf.d/ntp-client</i>
658 <comment>Customize if you wish but the defaults should be fine</comment>
659 # <i>rc-update add ntp-client default</i>
660
661 # <i>nano /etc/ntp.conf</i>
662 <comment>Add the follwing lines:</comment>
663 restrict default ignore
664 restrict 192.168.0.0 mask 255.255.255.0 notrust nomodify notrap
665 <comment>These will allow only ntp clients with an IP
666 address in the 192.168.0.xxx range to use your ntp server</comment>
667 # <i>nano /etc/conf.d/ntpd</i>
668 <comment>Customize if you wish but the defaults should be fine</comment>
669 # <i>rc-update add ntpd default</i>
670
671 # <i>/etc/init.d/ntp-client start</i>
672 # <i>/etc/init.d/ntpd start</i>
673 </pre>
674
675 <note>
676 You should make sure that you allow inbound and outbound communication on the
677 ntp port (123/udp) when setting up the server. The client just needs outbound
678 access on port 123 over udp.
679 </note>
680
681 <p>
682 Now, on your clients, have them <c>emerge ntp</c> also. However, we will just
683 run the ntp client so setup is a lot simpler.
684 </p>
685
686 <pre caption="Setting up a NTP client">
687 # <i>nano /etc/conf.d/ntp-client</i>
688 <comment>Change the 'pool.ntp.org' server in the NTPCLIENT_OPTS variable to '192.168.0.1'</comment>
689 # <i>rc-update add ntp-client default</i>
690 # <i>/etc/init.d/ntp-client start</i>
691 </pre>
692
693 </body>
694 </section>
695
696 <section>
697 <title>Rsync Server</title>
698 <body>
699
700 <p>
701 For those who run multiple Gentoo boxes on the same lan, you often want to
702 keep from having every machine running <c>emerge sync</c> with remote
703 servers. By setting up a local rsync, you save on both your bandwidth and
704 the Gentoo rsync servers' bandwidth. It's pretty simple to do.
705 </p>
706 <note>
707 For a much more in-depth rsync guide, please see the official <uri
708 link="/doc/en/rsync.xml#doc_chap4">rsync guide</uri>
709 </note>
710
711 <p>
712 Since every Gentoo machine requires rsync, theres no need to emerge it. Edit
713 the default <path>/etc/rsyncd.conf</path> config file, uncomment the
714 <c>[gentoo-portage]</c> section, and make sure you add an <c>address</c>
715 option. All the other defaults should be fine.
716 </p>
717
718 <pre caption="Rsync server config">
719 pid file = /var/run/rsyncd.pid
720 use chroot = yes
721 read only = yes
722 address = 192.168.0.1
723
724 [gentoo-portage]
725 path = /mnt/space/portage
726 comment = Gentoo Linux Portage tree
727 exclude = /distfiles /packages
728 </pre>
729
730 <p>
731 Then you need to start the service (again, the defaults are OK).
732 </p>
733
734 <pre caption="Starting the rsync server">
735 # <i>/etc/init.d/rsyncd start</i>
736 # <i>rc-update add rsyncd default</i>
737 </pre>
738
739 <p>
740 Only thing left is to set tell your clients to sync against the router.
741 </p>
742
743 <pre caption="Client SYNC settings in make.conf">
744 SYNC="rsync://192.168.0.1/gentoo-portage"
745 </pre>
746
747 </body>
748 </section>
749
750 <section>
751 <title>Mail Server</title>
752 <body>
753
754 <p>
755 Sometimes it's nice to run your own Simple Mail Transfer Protocol (SMTP) server
756 on the router. You may have your own reason for wanting to do so, but I run it
757 so that the users see mail as being sent instantly and the work of
758 retrying/routing is left up to the mail server. Some ISPs also don't allow for
759 mail relaying for accounts that aren't part of their network (like Verizon).
760 Also, you can easily throttle the delivery of mail so that large attachments
761 won't seriously lag your connection for half an hour.
762 </p>
763
764 <pre caption="Setting up SMTP">
765 # <i>emerge qmail</i>
766 <comment>make sure the output of `hostname` is correct</comment>
767 # <i>ebuild /var/db/pkg/*-*/qmail-1.03-r*/*.ebuild config</i>
768 # <i>iptables -I INPUT -p tcp --dport smtp -i ! ${LAN} -j REJECT</i>
769 # <i>ln -s /var/qmail/supervise/qmail-send /service/qmail-send</i>
770 # <i>ln -s /var/qmail/supervise/qmail-smtpd /service/qmail-smtpd</i>
771 <!--
772 # <i>cd /etc/tcprules.d</i>
773 # <i>nano tcp.qmail-smtp</i>
774 -->
775 # <i>cd /etc</i>
776 # <i>nano tcp.smtp</i>
777 <comment>Add an entry like so to the allow section:</comment>
778 192.168.0.:allow,RELAYCLIENT=""
779 <!--
780 # <i>tcprules tcp.qmail-qmtp.cdb rules.tmp &lt; tcp.qmail-smtp</i>
781 -->
782 # <i>tcprules tcp.smtp.cdb rules.tmp &lt; tcp.smtp</i>
783 # <i>rc-update add svscan default</i>
784 # <i>/etc/init.d/svscan start</i>
785 </pre>
786
787 <p>
788 I'm a huge fan of qmail, but you're free to use a different mta :). When you
789 setup e-mail on the hosts in your network, tell them that their SMTP server is
790 192.168.0.1 and everything should be peachy. You might want to visit the <uri
791 link="http://qmail.org/">qmail homepage</uri> for more documentation.
792 </p>
793
794 </body>
795 </section>
796
797 <!--
798 <section>
799 <title>E-mail Virus Scanning</title>
800 <body>
801 <p>
802 If you'd like to provide e-mail virus scanning for your users, but
803 don't want to have to install a virus scanner on every single machine,
804 then <c>pop3vscan</c> may just be the thing for you; a transparent
805 Post Office Protocol (POP) scanner.
806 </p>
807
808 <pre caption="Setting up pop3vscan">
809 TODO
810 </pre>
811
812 </body>
813 </section>
814 -->
815
816 <section>
817 <title>Full DHCP Server</title>
818 <body>
819
820 <p>
821 Earlier we used dnsmasq to provide DHCP service to all our clients. For most
822 people with a simple small LAN, this is perfect. But you may need something
823 with more features. Thus we turn to a full-featured DHCP server as provided
824 by the <uri link="http://www.isc.org/products/DHCP">ISC</uri> folks.
825 </p>
826
827 <pre caption="Setting up dhcpd">
828 # <i>emerge dhcp</i>
829 # <i>nano /etc/dhcp/dhcpd.conf</i>
830 <comment>(Here is a sample configuration file:)</comment>
831 authoritative;
832 ddns-update-style interim;
833 subnet 192.168.0.0 netmask 255.255.255.0 {
834 range 192.168.0.100 192.168.0.250;
835 default-lease-time 259200;
836 max-lease-time 518400;
837 option subnet-mask 255.255.255.0;
838 option broadcast-address 192.168.0.255;
839 option routers 192.168.0.1;
840 option domain-name-servers 192.168.0.1;
841 }
842 # <i>nano /etc/conf.d/dhcp</i>
843 <comment>(Set IFACE="eth0")</comment>
844 # <i>rc-update add dhcp default</i>
845 # <i>/etc/init.d/dhcp start</i>
846 </pre>
847
848 <p>
849 This is the minimal setup required to replace the dnsmasq DHCP functionality
850 that we used earlier. Speaking of which, you did remember to disable the DHCP
851 features in dnsmasq didn't you? If not, you should do so now (just comment
852 out the <c>dhcp-range</c> setting in <path>/etc/dnsmasq.conf</path> and restart
853 the service).
854 </p>
855
856 </body>
857 </section>
858
859 </chapter>
860
861 <chapter>
862 <title>Troubleshooting</title>
863
864 <section>
865 <title>Useful Tools</title>
866 <body>
867
868 <p>
869 If you're having trouble getting your computers to communicate, you may way to
870 try out the following tools (they can all be found in the <c>net-analyzer</c>
871 portage category):
872 </p>
873
874 <table>
875 <tr>
876 <th>Utility</th>
877 <th>Description</th>
878 </tr>
879 <tr>
880 <ti>ethereal</ti>
881 <ti>GUI tool to view all raw network data according to filters</ti>
882 </tr>
883 <tr>
884 <ti>tcpdump</ti>
885 <ti>Console tool to dump all raw network data according to filters</ti>
886 </tr>
887 <tr>
888 <ti>iptraf</ti>
889 <ti>ncurses based IP LAN monitor</ti>
890 </tr>
891 <tr>
892 <ti>ettercap</ti>
893 <ti>ncurses based network monitor/control</ti>
894 </tr>
895 </table>
896
897 </body>
898 </section>
899
900 <section>
901 <title>DHCP Fails To Start</title>
902 <body>
903
904 <p>
905 When starting the dhcp init.d script for the first time, it may fail to load
906 but neglect to give you any useful info.
907 </p>
908
909 <pre caption="DHCP Failing Example">
910 # <i>/etc/init.d/dhcp start</i>
911 * Setting ownership on dhcp.leases ... [ ok ]
912 * Starting dhcpd ... [ !! ]
913 </pre>
914
915 <p>
916 The trick is to know where dhcpd is sending its output. Simply browse to
917 /var/log and read the log files. Since the exact log file depends on the
918 package you are using as a syslog, try running <c>grep -Rl dhcpd /var/log</c>
919 to narrow down the possibilities. Chances are you made a typo in your config
920 file. You could also try running <c>dhcpd -d -f</c> (short for debug /
921 foreground) and debug the error based upon the output.
922 </p>
923
924 </body>
925 </section>
926
927 <section>
928 <title>Incorrect MTU Value</title>
929 <body>
930
931 <p>
932 If you experience odd errors (such as not being some webpages while others
933 load fine), you may be having Path MTU Discovery trouble. The quick way to
934 test is to run this iptables command:
935 </p>
936
937 <pre caption="Circumvent MTU issues">
938 # <i>iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu</i>
939 </pre>
940
941 <p>
942 This will affect all new connections, so just refresh the website you're
943 having problems with in order to test. In case it helps, the standard MTU
944 value for 100mbit ethernet connections is <c>1500</c> while for PPPoE
945 connections it is <c>1492</c>. For more info, you should read Chapter 15
946 of the <uri link="http://lartc.org/howto/">Linux Advanced Routing &amp;
947 Traffic Control HOWTO</uri>.
948 </p>
949
950 </body>
951 </section>
952
953 </chapter>
954
955 <chapter>
956 <title>Final Notes</title>
957 <section>
958 <body>
959
960 <p>
961 I have no final notes other than if you experience any troubles with the guide,
962 please contact <mail link="vapier@gentoo.org">me</mail> or file a bug with <uri
963 link="http://bugs.gentoo.org/">Gentoo's Bugtracking Website</uri>. If you have
964 some interesting bits you think would enhance this guide, by all means send it
965 my way for inclusion.
966 </p>
967
968 </body>
969 </section>
970 </chapter>
971 </guide>

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