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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 1.31 2005/08/17 22:42:01 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>1.12</version>
19 <date>2005-09-05</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 (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 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 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>Setup default policies to handle not matched by any rules</comment>
417 # <i>iptables -P INPUT ACCEPT</i>
418 # <i>iptables -P OUTPUT ACCEPT</i>
419 # <i>iptables -P FORWARD DROP</i>
420
421 <comment>Copy and paste these examples ...</comment>
422 # <i>export LAN=eth0</i>
423 # <i>export WAN=eth1</i>
424
425 <comment>Then we lock our services so they only work from the LAN</comment>
426 # <i>iptables -I INPUT 1 -i ${LAN} -j ACCEPT</i>
427 # <i>iptables -I INPUT 1 -i lo -j ACCEPT</i>
428 # <i>iptables -A INPUT -p UDP --dport bootps -i ! ${LAN} -j REJECT</i>
429 # <i>iptables -A INPUT -p UDP --dport domain -i ! ${LAN} -j REJECT</i>
430
431 <comment>(Optional) Allow access to our ssh server from the WAN</comment>
432 # <i>iptables -A INPUT -p TCP --dport ssh -i ${WAN} -j ACCEPT</i>
433
434 <comment>Drop TCP / UDP packets to privileged ports</comment>
435 # <i>iptables -A INPUT -p TCP -i ! ${LAN} -d 0/0 --dport 0:1023 -j DROP</i>
436 # <i>iptables -A INPUT -p UDP -i ! ${LAN} -d 0/0 --dport 0:1023 -j DROP</i>
437
438 <comment>Finally we add the rules for NAT</comment>
439 # <i>iptables -I FORWARD -i ${LAN} -d 192.168.0.0/255.255.0.0 -j DROP</i>
440 # <i>iptables -A FORWARD -i ${LAN} -s 192.168.0.0/255.255.0.0 -j ACCEPT</i>
441 # <i>iptables -A FORWARD -i ${WAN} -d 192.168.0.0/255.255.0.0 -j ACCEPT</i>
442 # <i>iptables -t nat -A POSTROUTING -o ${WAN} -j MASQUERADE</i>
443 <comment>Tell the kernel that ip forwarding is OK</comment>
444 # <i>echo 1 > /proc/sys/net/ipv4/ip_forward</i>
445 # <i>for f in /proc/sys/net/ipv4/conf/*/rp_filter ; do echo 1 > $f ; done</i>
446
447 <comment>This is so when we boot we don't have to run the rules by hand</comment>
448 # <i>/etc/init.d/iptables save</i>
449 # <i>rc-update add iptables default</i>
450 # <i>nano /etc/sysctl.conf</i>
451 <comment>Add/Uncomment the following lines:
452 net.ipv4.ip_forward = 1
453 net.ipv4.conf.default.rp_filter = 1</comment>
454 </pre>
455
456 <p>
457 Once you've typed out all of that, the rest of your network should now be able
458 to use the internet as if they were directly connected themselves.
459 </p>
460
461 </body>
462 </section>
463 </chapter>
464
465 <chapter>
466 <title>Fun Things (for a rainy day)</title>
467
468 <section>
469 <title>Intro</title>
470 <body>
471
472 <p>
473 Believe it or not, you're done :). From here on out, I'll cover a bunch of
474 common topics that may interest you. Everything in this chapter is completely
475 optional.
476 </p>
477
478 </body>
479 </section>
480
481 <section>
482 <title>Port Forwarding</title>
483 <body>
484
485 <p>
486 Sometimes you would like to be able to host services on a computer behind the
487 router, or just to make your life easier when connecting remotely. Perhaps you
488 want to run a FTP, HTTP, SSH, or VNC server on one or more machines behind your
489 router and be able to connect to them all. The only caveat is that you can
490 only have one service/machine combo per port. For example, there is no
491 practical way to setup three FTP servers behind your router and then try to
492 connect to them all through port 21; only one can be on port 21 while the
493 others would have to be on say port 123 and port 567.
494 </p>
495
496 <p>
497 All the port forwarding rules are of the form <c>iptables -t nat -A PREROUTING
498 [-p protocol] --dport [external port on router] -i ${WAN} -j DNAT --to [ip/port
499 to forward to]</c>. iptables does not accept hostnames when port forwarding.
500 If you are forwarding an external port to the same port on the internal
501 machine, you can omit the destination port. See the iptables(8) page for more
502 information.
503 </p>
504
505 <pre caption="Running the iptables commands">
506 <comment>Copy and paste these examples ...</comment>
507 # <i>export LAN=eth0</i>
508 # <i>export WAN=eth1</i>
509
510 <comment>Forward port 2 to ssh on an internal host</comment>
511 # <i>iptables -t nat -A PREROUTING -p tcp --dport 2 -i ${WAN} -j DNAT --to 192.168.0.2:22</i>
512
513 <comment>FTP forwarding to an internal host</comment>
514 # <i>iptables -t nat -A PREROUTING -p tcp --dport 21 -i ${WAN} -j DNAT --to 192.168.0.56</i>
515
516 <comment>HTTP forwarding to an internal host</comment>
517 # <i>iptables -t nat -A PREROUTING -p tcp --dport 80 -i ${WAN} -j DNAT --to 192.168.0.56</i>
518
519 <comment>VNC forwarding for internal hosts</comment>
520 # <i>iptables -t nat -I PREROUTING -p tcp --dport 5900 -i ${WAN} -j DNAT --to 192.168.0.2</i>
521 # <i>iptables -t nat -I PREROUTING -p tcp --dport 5901 -i ${WAN} -j DNAT --to 192.168.0.3:5900</i>
522 <comment>If you want to VNC in to 192.168.0.3, then just add ':1' to the router's hostname</comment>
523
524 <comment>Bittorrent forwarding</comment>
525 # <i>iptables -t nat -A PREROUTING -p tcp --dport 6881:6889 -i ${WAN} -j DNAT --to 192.168.0.2</i>
526
527 <comment>Game Cube Warp Pipe support</comment>
528 # <i>iptables -t nat -A PREROUTING -p udp --dport 4000 -i ${WAN} -j DNAT --to 192.168.0.56</i>
529
530 <comment>Playstation2 Online support</comment>
531 # <i>iptables -t nat -A PREROUTING -p tcp --dport 10070:10080 -i ${WAN} -j DNAT --to 192.168.0.11</i>
532 # <i>iptables -t nat -A PREROUTING -p udp --dport 10070:10080 -i ${WAN} -j DNAT --to 192.168.0.11</i>
533 </pre>
534
535 <note>
536 If you have other common / cool examples, please <uri
537 link="mailto:vapier@gentoo.org">e-mail me</uri>.
538 </note>
539
540 </body>
541 </section>
542
543 <section>
544 <title>Identd (for IRC)</title>
545 <body>
546
547 <p>
548 Internet Relay Chat utilizes the ident service pretty heavily. Now that the
549 IRC clients are behind the router, we need a way to host ident for both the
550 router and the clients. One such server has been created called
551 <c>midentd</c>.
552 </p>
553
554 <pre caption="Setting up ident">
555 # <i>emerge midentd</i>
556 # <i>rc-update add midentd default</i>
557 # <i>/etc/init.d/midentd start</i>
558 </pre>
559
560 <p>
561 There are a few other ident servers in portage. Depending on your needs, I
562 would recommend checking out <c>oidentd</c> and <c>fakeidentd</c>.
563 </p>
564
565 </body>
566 </section>
567
568 <!--
569 <section>
570 <title>Traffic Shaping</title>
571 <body>
572 <p>
573 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>
574 found over at the TLDP. Feel free to refer to the original document
575 for more details.
576 </p>
577
578 <p>
579 Here we will be setting up what some people refer to as a "Packet Shaper",
580 <uri link="http://en.wikipedia.org/wiki/Traffic_shaping">"Traffic Shaping"</uri>,
581 or <uri link="http://en.wikipedia.org/wiki/QoS">"Quality of Service"</uri>.
582 Simply put, we want to setup rules on our router that will slow down
583 certain activities (like sending large e-mails or downloading from P2P
584 networks) while keeping other activities (like browsing the web or playing
585 online video games) reasonably fast. A 30 second difference in a video
586 game is a lot worse than a 30 second difference in downloading large
587 files :).
588 </p>
589
590 <p>
591 The first thing is to make sure your kernel has all the features added to
592 it. See the chapter on <uri link="#doc_chap2">Kernel setup</uri> for more
593 information. Next, you will need to <c>emerge iptables iputils</c> so that
594 you will have access to the <c>iptables</c>, <c>ip</c>, and <c>tc</c>
595 commands.
596 </p>
597
598 <p>
599 Before we jump into the commands, let's cover a little of the theory. The
600 way this whole system works is to classify common network streams and then
601 to prioritize them. You use iptables to classify network streams, iputils
602 to define the different priority levels, and the kernel to adjust speeds.
603 Just remember that although you can control outbound traffic pretty tightly
604 (from the LAN to the WAN), your ability to control inbound traffic (from
605 the WAN to the LAN) is somewhat limited. Just remember that the following
606 examples are to get your feet wet; if you want more then I'd suggest
607 reading up on the subject. In this example, we will be using the
608 <uri link="http://luxik.cdi.cz/~devik/qos/htb/">Hierarchical Token Buckets (HTB)</uri>
609 packet scheduling algorithm. Still with me? Great, let's start shaping :).
610 </p>
611
612 <pre caption="Setup">
613 DEV=eth1 <comment>NIC connected to WAN</comment>
614 RATE_OUT=100 <comment>Available outbound bandwidth (in kilobits [kb])</comment>
615 RATE_IN=1400 <comment>Available inbound bandwidth (in kb)</comment>
616
617 <comment>Here we initialize the priority system. The 45 is used to set the default classification level.</comment>
618 ip link set dev ${DEV} qlen 30
619 tc qdisc add dev ${DEV} root handle 1: htb default 45
620 tc class add dev ${DEV} parent 1: classid 1:1 htb rate ${RATE_OUT}kbit
621 </pre>
622
623 <p>
624 Here we initialized the system which will be used to prioritize all of
625 our network traffic. We created our queue, told it to use the HTB
626 algorithm, and set the default classification level to '45'. The
627 default is completely arbitrary, as are the levels we choose from
628 here on out. The only thing that matters is how the levels compare
629 relatively; a level '10' packet will be given preference over a
630 level '45' packet. Let's move on to declaring different levels.
631 </p>
632
633 <pre caption="Declaring levels">
634 tc class add dev $DEV parent 1:1 classid 1:10 htb rate $rkbit ceil $tkbit prio $p
635 tc qdisc add dev $DEV parent 1:10 handle 10: sfq
636 </pre>
637 </body>
638 </section>
639 -->
640
641 <section>
642 <title>Time Server</title>
643 <body>
644
645 <p>
646 Keeping your system time correct is essential in maintaining a healthy system.
647 One of the most common ways of accomplishing this is with the Network Time
648 Protocol (NTP) and the ntp package (which provides implementations for both
649 server and client).
650 </p>
651
652 <p>
653 Many people run ntp clients on their computers. Obviously, the more clients in
654 the world, the larger the load the ntp servers need to shoulder. In
655 environments like home networks though, we can help keep the load down on
656 public servers while still providing the proper time to all our computers. As
657 an added bonus, our private updates will be a lot faster for the clients too!
658 All we have to do is run a ntp server on our router that synchronizes itself
659 with the public internet servers while providing the time to the rest of the
660 computers in the network. To get started, simply <c>emerge ntp</c> on the
661 router.
662 </p>
663
664 <pre caption="Setting up the NTP server">
665 # <i>nano /etc/conf.d/ntp-client</i>
666 <comment>Customize if you wish but the defaults should be fine</comment>
667 # <i>rc-update add ntp-client default</i>
668
669 # <i>nano /etc/ntp.conf</i>
670 <comment>Add the follwing lines:</comment>
671 restrict default ignore
672 restrict 192.168.0.0 mask 255.255.255.0 notrust nomodify notrap
673 <comment>These will allow only ntp clients with an IP
674 address in the 192.168.0.xxx range to use your ntp server</comment>
675 # <i>nano /etc/conf.d/ntpd</i>
676 <comment>Customize if you wish but the defaults should be fine</comment>
677 # <i>rc-update add ntpd default</i>
678
679 # <i>/etc/init.d/ntp-client start</i>
680 # <i>/etc/init.d/ntpd start</i>
681 </pre>
682
683 <note>
684 You should make sure that you allow inbound and outbound communication on the
685 ntp port (123/udp) when setting up the server. The client just needs outbound
686 access on port 123 over udp.
687 </note>
688
689 <p>
690 Now, on your clients, have them <c>emerge ntp</c> also. However, we will just
691 run the ntp client so setup is a lot simpler.
692 </p>
693
694 <pre caption="Setting up a NTP client">
695 # <i>nano /etc/conf.d/ntp-client</i>
696 <comment>Change the 'pool.ntp.org' server in the NTPCLIENT_OPTS variable to '192.168.0.1'</comment>
697 # <i>rc-update add ntp-client default</i>
698 # <i>/etc/init.d/ntp-client start</i>
699 </pre>
700
701 </body>
702 </section>
703
704 <section>
705 <title>Rsync Server</title>
706 <body>
707
708 <p>
709 For those who run multiple Gentoo boxes on the same lan, you often want to
710 keep from having every machine running <c>emerge sync</c> with remote
711 servers. By setting up a local rsync, you save on both your bandwidth and
712 the Gentoo rsync servers' bandwidth. It's pretty simple to do.
713 </p>
714 <note>
715 For a much more in-depth rsync guide, please see the official <uri
716 link="/doc/en/rsync.xml#doc_chap4">rsync guide</uri>
717 </note>
718
719 <p>
720 Since every Gentoo machine requires rsync, theres no need to emerge it. Edit
721 the default <path>/etc/rsyncd.conf</path> config file, uncomment the
722 <c>[gentoo-portage]</c> section, and make sure you add an <c>address</c>
723 option. All the other defaults should be fine.
724 </p>
725
726 <pre caption="Rsync server config">
727 pid file = /var/run/rsyncd.pid
728 use chroot = yes
729 read only = yes
730 address = 192.168.0.1
731
732 [gentoo-portage]
733 path = /mnt/space/portage
734 comment = Gentoo Linux Portage tree
735 exclude = /distfiles /packages
736 </pre>
737
738 <p>
739 Then you need to start the service (again, the defaults are OK).
740 </p>
741
742 <pre caption="Starting the rsync server">
743 # <i>/etc/init.d/rsyncd start</i>
744 # <i>rc-update add rsyncd default</i>
745 </pre>
746
747 <p>
748 Only thing left is to set tell your clients to sync against the router.
749 </p>
750
751 <pre caption="Client SYNC settings in make.conf">
752 SYNC="rsync://192.168.0.1/gentoo-portage"
753 </pre>
754
755 </body>
756 </section>
757
758 <section>
759 <title>Mail Server</title>
760 <body>
761
762 <p>
763 Sometimes it's nice to run your own Simple Mail Transfer Protocol (SMTP) server
764 on the router. You may have your own reason for wanting to do so, but I run it
765 so that the users see mail as being sent instantly and the work of
766 retrying/routing is left up to the mail server. Some ISPs also don't allow for
767 mail relaying for accounts that aren't part of their network (like Verizon).
768 Also, you can easily throttle the delivery of mail so that large attachments
769 won't seriously lag your connection for half an hour.
770 </p>
771
772 <pre caption="Setting up SMTP">
773 # <i>emerge qmail</i>
774 <comment>make sure the output of `hostname` is correct</comment>
775 # <i>ebuild /var/db/pkg/*-*/qmail-1.03-r*/*.ebuild config</i>
776 # <i>iptables -I INPUT -p tcp --dport smtp -i ! ${LAN} -j REJECT</i>
777 # <i>ln -s /var/qmail/supervise/qmail-send /service/qmail-send</i>
778 # <i>ln -s /var/qmail/supervise/qmail-smtpd /service/qmail-smtpd</i>
779 <!--
780 # <i>cd /etc/tcprules.d</i>
781 # <i>nano tcp.qmail-smtp</i>
782 -->
783 # <i>cd /etc</i>
784 # <i>nano tcp.smtp</i>
785 <comment>Add an entry like so to the allow section:</comment>
786 192.168.0.:allow,RELAYCLIENT=""
787 <!--
788 # <i>tcprules tcp.qmail-qmtp.cdb rules.tmp &lt; tcp.qmail-smtp</i>
789 -->
790 # <i>tcprules tcp.smtp.cdb rules.tmp &lt; tcp.smtp</i>
791 # <i>rc-update add svscan default</i>
792 # <i>/etc/init.d/svscan start</i>
793 </pre>
794
795 <p>
796 I'm a huge fan of qmail, but you're free to use a different mta :). When you
797 setup e-mail on the hosts in your network, tell them that their SMTP server is
798 192.168.0.1 and everything should be peachy. You might want to visit the <uri
799 link="http://qmail.org/">qmail homepage</uri> for more documentation.
800 </p>
801
802 </body>
803 </section>
804
805 <!--
806 <section>
807 <title>E-mail Virus Scanning</title>
808 <body>
809 <p>
810 If you'd like to provide e-mail virus scanning for your users, but
811 don't want to have to install a virus scanner on every single machine,
812 then <c>pop3vscan</c> may just be the thing for you; a transparent
813 Post Office Protocol (POP) scanner.
814 </p>
815
816 <pre caption="Setting up pop3vscan">
817 TODO
818 </pre>
819
820 </body>
821 </section>
822 -->
823
824 </chapter>
825
826 <chapter>
827 <title>Troubleshooting</title>
828
829 <section>
830 <title>Useful Tools</title>
831 <body>
832
833 <p>
834 If you're having trouble getting your computers to communicate, you may way to
835 try out the following tools (they can all be found in the <c>net-analyzer</c>
836 portage category):
837 </p>
838
839 <table>
840 <tr>
841 <th>Utility</th>
842 <th>Description</th>
843 </tr>
844 <tr>
845 <ti>ethereal</ti>
846 <ti>GUI tool to view all raw network data according to filters</ti>
847 </tr>
848 <tr>
849 <ti>tcpdump</ti>
850 <ti>Console tool to dump all raw network data according to filters</ti>
851 </tr>
852 <tr>
853 <ti>iptraf</ti>
854 <ti>ncurses based IP LAN monitor</ti>
855 </tr>
856 <tr>
857 <ti>ettercap</ti>
858 <ti>ncurses based network monitor/control</ti>
859 </tr>
860 </table>
861
862 </body>
863 </section>
864
865 <section>
866 <title>DHCP Fails To Start</title>
867 <body>
868
869 <p>
870 When starting the dhcp init.d script for the first time, it may fail to load
871 but neglect to give you any useful info.
872 </p>
873
874 <pre caption="DHCP Failing Example">
875 # <i>/etc/init.d/dhcp start</i>
876 * Setting ownership on dhcp.leases ... [ ok ]
877 * Starting dhcpd ... [ !! ]
878 </pre>
879
880 <p>
881 The trick is to know where dhcpd is sending its output. Simply browse to
882 /var/log and read the log files. Since the exact log file depends on the
883 package you are using as a syslog, try running <c>grep -Rl dhcpd /var/log</c>
884 to narrow down the possibilities. Chances are you made a typo in your config
885 file. You could also try running <c>dhcpd -d -f</c> (short for debug /
886 foreground) and debug the error based upon the output.
887 </p>
888
889 </body>
890 </section>
891
892 <section>
893 <title>Incorrect MTU Value</title>
894 <body>
895
896 <p>
897 If you experience odd errors (such as not being some webpages while others
898 load fine), you may be having Path MTU Discovery trouble. The quick way to
899 test is to run this iptables command:
900 </p>
901
902 <pre caption="Circumvent MTU issues">
903 # <i>iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu</i>
904 </pre>
905
906 <p>
907 This will affect all new connections, so just refresh the website you're
908 having problems with in order to test. In case it helps, the standard MTU
909 value for 100mbit ethernet connections is <c>1500</c> while for PPPoE
910 connections it is <c>1492</c>. For more info, you should read Chapter 15
911 of the <uri link="http://lartc.org/howto/">Linux Advanced Routing &amp;
912 Traffic Control HOWTO</uri>.
913 </p>
914
915 </body>
916 </section>
917
918 </chapter>
919
920 <chapter>
921 <title>Final Notes</title>
922 <section>
923 <body>
924
925 <p>
926 I have no final notes other than if you experience any troubles with the guide,
927 please contact <mail link="vapier@gentoo.org">me</mail> or file a bug with <uri
928 link="http://bugs.gentoo.org/">Gentoo's Bugtracking Website</uri>. If you have
929 some interesting bits you think would enhance this guide, by all means send it
930 my way for inclusion.
931 </p>
932
933 </body>
934 </section>
935 </chapter>
936 </guide>

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