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1 <?xml version='1.0' encoding='UTF-8'?>
2 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
3 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/home-router-howto.xml,v 1.51 2006/08/21 10:50:14 vapier Exp $ -->
4
5 <guide link="/doc/en/home-router-howto.xml" lang="en">
6 <title>Home Router Guide</title>
7
8 <author title="Author">
9 <mail link="vapier@gentoo.org">Mike Frysinger</mail>
10 </author>
11
12 <abstract>
13 This document details how to turn an old Gentoo machine into a router
14 for connecting your home network to the internet.
15 </abstract>
16
17 <!-- The content of this document is released into the public domain -->
18 <license/>
19
20 <version>1.31</version>
21 <date>2006-08-21</date>
22
23 <chapter>
24 <title>Introduction</title>
25 <section>
26 <body>
27
28 <p>
29 Building your own router out of old spare parts has many advantages over buying
30 a pre-made canned router by say Linksys. The biggest one by far is control
31 over the connection. The other advantages are left up to your imagination;
32 just about anything can be done in this scenario, it's just a matter of needing
33 it.
34 </p>
35
36 <p>
37 This guide will show you how to setup Network Address Translation (NAT) on the
38 router (kernel and iptables), add and configure common services (Domain Name
39 System (DNS) via dnsmasq, dhcp via dhcpcd, ADSL via rp-pppoe), and conclude
40 with more elaborate and fun things that can be done (port forwarding, traffic
41 shaping, proxies/caching, etc...).
42 </p>
43
44 <p>
45 Before getting started, there's a few basic requirements you must meet. First,
46 you'll need a computer that has at least 2 Network Interface Cards (NICs) in
47 it. Next, you'll need the configuration settings for your internet connection
48 (may include things like IP/DNS/Gateway/username/password). Finally, you'll
49 need a bit of spare time and some Gentoo loving.
50 </p>
51
52 <p>
53 The conventions used in this guide are:
54 </p>
55
56 <ul>
57 <li>eth0 - NIC connected to the Local Area Network (LAN)</li>
58 <li>eth1 - NIC connected to the Wide Area Network (WAN)</li>
59 <li>LAN utilizes the private 192.168.0.xxx network</li>
60 <li>router is hardcoded to the standard 192.168.0.1 IP</li>
61 <li>router is running Linux 2.4 or 2.6; you're on your own with 2.0/2.2</li>
62 </ul>
63
64 <impo>
65 Due to security precautions, I would highly suggest you shut down any unneeded
66 services on the router until we have a chance to get the firewall up and
67 rolling. To view the currently running services, just run <c>rc-status</c>.
68 </impo>
69
70 </body>
71 </section>
72 </chapter>
73
74 <chapter>
75 <title>Kernel setup (know thyself first)</title>
76 <section>
77 <body>
78
79 <p>
80 Your kernel needs to have the drivers running for both your NICs. To see if
81 your cards are already setup, just run <c>ifconfig</c>. Your output may differ
82 slightly from the following, that's fine. What matters is that the interface
83 shows up at all.
84 </p>
85
86 <pre caption="Checking NICs">
87 # <i>ifconfig -a</i>
88 eth0 Link encap:Ethernet HWaddr 00:60:F5:07:07:B8
89 BROADCAST MULTICAST MTU:1500 Metric:1
90 RX packets:0 errors:0 dropped:0 overruns:0 frame:0
91 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
92 collisions:0 txqueuelen:1000
93 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
94 Interrupt:11 Base address:0x9800
95
96 eth1 Link encap:Ethernet HWaddr 00:60:F5:07:07:B9
97 BROADCAST MULTICAST MTU:1500 Metric:1
98 RX packets:0 errors:0 dropped:0 overruns:0 frame:0
99 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
100 collisions:0 txqueuelen:1000
101 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
102 Interrupt:10 Base address:0x9400
103 </pre>
104
105 <p>
106 If you do not see your two cards showing up and you're not sure what kind of
107 cards you have, try running <c>lspci | grep Ethernet</c>. You can get that
108 from <c>emerge pciutils</c>. Once you have this information, go into your
109 kernel and add support for the correct drivers.
110 </p>
111
112 <p>
113 The next thing you'll need is support for iptables and NAT (and packet shaping
114 if you want). The following list is split up into always required (*),
115 required only for adsl via PPPoE (a), suggested for everyone (x), and only
116 for shaper (s) features. It does not matter whether you build the features
117 into the kernel or as a module so long as when the feature is needed, the
118 correct module(s) are loaded (module loading is left to the reader as a fun
119 exercise however).
120 </p>
121
122 <pre caption="Network Options">
123 Networking options ---&gt;
124 [*] TCP/IP networking
125 [*] IP: advanced router
126 [*] Network packet filtering (replaces ipchains)
127 <comment>If you use 2.4.x, you have to enable the following for DHCP:</comment>
128 [*] Socket Filtering
129
130 IP: Netfilter Configuration ---&gt;
131 [*] Connection tracking (required for masq/NAT)
132 [x] FTP protocol support
133 [x] IRC protocol support
134 [*] IP tables support (required for filtering/masq/NAT)
135 [*] IP range match support
136 [x] MAC address match support
137 [*] Multiple port match support
138 [*] Packet filtering
139 [*] REJECT target support
140 [x] REDIRECT target support
141 [*] Full NAT
142 [*] MASQUERADE target support
143 [s] Packet mangling
144 [s] MARK target support
145 [x] LOG target support
146
147 QoS and/or fair queueing ---&gt;
148 [s] QoS and/or fair queueing
149 [s] HTB packet scheduler
150 [s] Ingress Qdisc
151
152 [a] PPP (point-to-point protocol) support
153 [a] PPP filtering
154 [a] PPP support for async serial ports
155 [a] PPP support for sync tty ports
156 [a] PPP Deflate compression
157 [a] PPP BSD-Compress compression
158 [a] PPP over Ethernet
159 </pre>
160
161 <note>
162 Some things may be slightly different in a 2.4 vs 2.6 kernel, but you should be
163 able to figure it out :). Even among 2.6 kernels, these options have a
164 tendency to move around. Good luck!
165 </note>
166
167 </body>
168 </section>
169 </chapter>
170
171 <chapter>
172 <title>Hug the WAN (a.k.a. The Internet)</title>
173
174 <section>
175 <title>Intro</title>
176 <body>
177
178 <p>
179 There are many ways to connect to the internet so I'll just cover the ones I'm
180 familiar with. That leaves us with ADSL (PPPoE) and cable modems
181 (static/dynamic). If there are other methods out there, feel free to write up
182 a little blurb and e-mail me. Feel free to skip any of the following sections
183 in this chapter that don't apply to you. This chapter is just about getting
184 the router connected to the internet via eth1.
185 </p>
186
187 </body>
188 </section>
189 <section>
190 <title>ADSL and PPPoE</title>
191 <body>
192
193 <p>
194 All the fancy PPPoE software has been bundled up into one little nice package
195 nowadays called <uri link="http://www.roaringpenguin.com/">Roaring
196 Penguin</uri>. Simply <c>emerge rp-pppoe</c> and you'll be on your way.
197 Remember how I said you'll need username/password information? Well I wasn't
198 lying so I hope you have it now! Load up <path>/etc/ppp/pppoe.conf</path> in
199 your favorite editor and set it up.
200 </p>
201
202 <note>
203 In order for the following net settings to work, you must have
204 baselayout-1.11.14 or later installed on your system.
205 </note>
206
207 <pre caption="Setting up eth1">
208 <comment>(Replace 'vla9h924' with your username and 'password' with your password)</comment>
209
210 # <i>nano /etc/ppp/pap-secrets</i>
211 <comment># client server secret</comment>
212 "vla9h924" * "password"
213 # <i>nano /etc/conf.d/net</i>
214 <comment>Tell baselayout to use adsl for your eth1:</comment>
215 config_eth1=( "adsl" )
216 user_eth1=( "vla9h924" )
217 # <i>ln -s net.lo /etc/init.d/net.eth1</i>
218 # <i>rc-update add net.eth1 default</i>
219 # <i>/etc/init.d/net.eth1 start</i>
220 </pre>
221
222 <warn>
223 When the DSL interface comes up, it will create ppp0. Although your NIC is
224 called eth1, the IP is actually bound to ppp0. From now on, when you see
225 examples that utilize 'eth1', substitute with 'ppp0'.
226 </warn>
227
228 </body>
229 </section>
230
231 <section>
232 <title>Cable and/or dynamic/static IP</title>
233 <body>
234
235 <p>
236 If you have a static IP then you will need a few more details than if
237 you have a dynamic IP. For static users, you will need your IP,
238 gateway, and DNS servers.
239 </p>
240
241 <pre caption="Setting up eth1">
242 <comment>Dynamic IP Users:</comment>
243 # <i>emerge dhcpcd</i>
244 # <i>nano /etc/conf.d/net</i>
245 <comment>You'll need an entry like so:</comment>
246 config_eth1=( "dhcp" )
247
248 <comment>Static IP Users:</comment>
249 # <i>nano /etc/conf.d/net</i>
250 <comment>You'll need entries like so:</comment>
251 config_eth1=( "66.92.78.102 broadcast 66.92.78.255 netmask 255.255.255.0" )
252 routes_eth1=( "default gw 66.92.78.1" )
253 # <i>nano /etc/resolv.conf</i>
254 <comment>Add one line per DNS server:</comment>
255 nameserver 123.123.123.123
256
257 <comment>Dynamic and Static Setup:</comment>
258 # <i>ln -s net.lo /etc/init.d/net.eth1</i>
259 # <i>rc-update add net.eth1 default</i>
260 # <i>/etc/init.d/net.eth1 start</i>
261 </pre>
262
263 <p>
264 You should be all set to go now.
265 </p>
266
267 </body>
268 </section>
269 </chapter>
270
271 <chapter>
272 <title>Hug the LAN (bring along some friends)</title>
273 <section>
274 <body>
275
276 <p>
277 This step is a breeze compared to the previous one.
278 </p>
279
280 <pre caption="Setting up eth0">
281 # <i>nano /etc/conf.d/net</i>
282 <comment>Add a line like the following:</comment>
283 config_eth0=( "192.168.0.1 broadcast 192.168.0.255 netmask 255.255.255.0" )
284 # <i>rc-update add net.eth0 default</i>
285 # <i>/etc/init.d/net.eth0 start</i>
286 </pre>
287
288 </body>
289 </section>
290 </chapter>
291
292 <chapter>
293 <title>LAN Services (because we're nice people)</title>
294
295 <section>
296 <title>DHCP Server</title>
297 <body>
298
299 <p>
300 I bet it'd be nice if everyone else in your house could just plug their
301 computers into the network and things would just work. No need to remember
302 mind-numbing details or make them stare at confusing configuration screens!
303 Life would be grand eh? Introducing the Dynamic Host Configuration Protocol
304 (DHCP) and why you should care.
305 </p>
306
307 <p>
308 DHCP is exactly what its name implies. It's a protocol that allows you
309 to dynamically configure other hosts automatically. You run a DHCP server on
310 the router, give it all the information about your network (valid IPs,
311 DNS servers, gateways, etc...), and then when the other hosts start up, they
312 run a DHCP client to automatically configure themselves. No fuss, no muss!
313 For more information about DHCP, you can always visit <uri
314 link="http://en.wikipedia.org/wiki/DHCP">Wikipedia</uri>.
315 </p>
316
317 <p>
318 We'll use a package called dnsmasq which provides both DHCP and DNS services.
319 For now lets just focus on the DHCP aspect. Note that if you want to run a
320 different DHCP server, you can find another example in the Fun Things chapter.
321 Also, if you wish to tinker with the DHCP server settings, just read the
322 comments in <path>/etc/dnsmasq.conf</path>. All the defaults should work fine
323 though.
324 </p>
325
326 <pre caption="Setting up a DHCP server">
327 # <i>emerge dnsmasq</i>
328 # <i>nano /etc/dnsmasq.conf</i>
329 <comment>Add this line to enable dhcp:</comment>
330 dhcp-range=192.168.0.100,192.168.0.250,72h
331 <comment>Restrict dnsmasq to just the LAN interface</comment>
332 interface=eth0
333
334 # <i>rc-update add dnsmasq default</i>
335 # <i>/etc/init.d/dnsmasq start</i>
336 </pre>
337
338 <p>
339 Now your little router is a bona-fide DHCP server! Plugin those computers and
340 watch them work! With Windows systems you should go into the TCP/IP Properties
341 and select the 'Obtain an IP address automatically' and 'Obtain DNS server
342 address automatically' options. Sometimes the changes aren't instantaneous, so
343 you may have to open a command prompt and run <c>ipconfig /release</c> and
344 <c>ipconfig /renew</c>. But enough about Windows, let's get back to our
345 favorite penguin.
346 </p>
347
348 </body>
349 </section>
350
351 <section>
352 <title>DNS Server</title>
353 <body>
354
355 <p>
356 When people want to visit a place on the internet, they remember names, not a
357 string of funky numbers. After all, what's easier to remember, ebay.com or
358 66.135.192.87? This is where the DNS steps in. DNS servers run all over the
359 internet, and whenever someone wants to visit 'ebay.com', these servers turn
360 'ebay.com' (what we understand) into '66.135.192.87' (what our computers
361 understand). For more information about DNS, you can always visit <uri
362 link="http://en.wikipedia.org/wiki/DNS">Wikipedia</uri>.
363 </p>
364
365 <p>
366 Since we're using dnsmasq for our DHCP server, and it includes a DNS server,
367 you've got nothing left to do here! Your little router is already providing
368 DNS to its DHCP clients. Bet you wish everything was this easy ;).
369 </p>
370
371 <p>
372 You're welcome to choose other DNS servers if you're more comfortable with
373 them, but the reason dnsmasq is great is because it was designed to do exactly
374 what we want and nothing more. It's a little DNS caching/forwarding server for
375 local networks. We're not looking to provide DNS for our own domain here, just
376 offer simple DNS services to everyone else on our LAN.
377 </p>
378
379 </body>
380 </section>
381
382 <section>
383 <title>NAT (a.k.a. IP-masquerading)</title>
384 <body>
385
386 <p>
387 At this point, people on your network can talk to each other and they can look
388 up hostnames via DNS, but they still can't actually connect to the internet.
389 While you may think that's great (more bandwidth for you!), I bet they're not
390 too happy just yet.
391 </p>
392
393 <p>
394 This is where Network Address Translation (NAT) steps in. NAT is a way of
395 connecting multiple computers in a private LAN to the internet when you have a
396 smaller number of public IP addresses available to you. Typically you are given
397 1 IP by your ISP, but you want to let your whole house connect to the internet.
398 NAT is the magic that makes this possible. For more information about NAT, you
399 can always visit <uri link="http://en.wikipedia.org/wiki/NAT">Wikipedia</uri>.
400 </p>
401
402 <note>
403 Before we get started, make sure you have iptables on your system. Although it
404 is automatically installed on most systems, you may not have it. If you don't,
405 just run <c>emerge iptables</c>.
406 </note>
407
408 <pre caption="Setting up iptables">
409 <comment>First we flush our current rules</comment>
410 # <i>iptables -F</i>
411 # <i>iptables -t nat -F</i>
412
413 <comment>Setup default policies to handle unmatched traffic</comment>
414 # <i>iptables -P INPUT ACCEPT</i>
415 # <i>iptables -P OUTPUT ACCEPT</i>
416 # <i>iptables -P FORWARD DROP</i>
417
418 <comment>Copy and paste these examples ...</comment>
419 # <i>export LAN=eth0</i>
420 # <i>export WAN=eth1</i>
421
422 <comment>Then we lock our services so they only work from the LAN</comment>
423 # <i>iptables -I INPUT 1 -i ${LAN} -j ACCEPT</i>
424 # <i>iptables -I INPUT 1 -i lo -j ACCEPT</i>
425 # <i>iptables -A INPUT -p UDP --dport bootps -i ! ${LAN} -j REJECT</i>
426 # <i>iptables -A INPUT -p UDP --dport domain -i ! ${LAN} -j REJECT</i>
427
428 <comment>(Optional) Allow access to our ssh server from the WAN</comment>
429 # <i>iptables -A INPUT -p TCP --dport ssh -i ${WAN} -j ACCEPT</i>
430
431 <comment>Drop TCP / UDP packets to privileged ports</comment>
432 # <i>iptables -A INPUT -p TCP -i ! ${LAN} -d 0/0 --dport 0:1023 -j DROP</i>
433 # <i>iptables -A INPUT -p UDP -i ! ${LAN} -d 0/0 --dport 0:1023 -j DROP</i>
434
435 <comment>Finally we add the rules for NAT</comment>
436 # <i>iptables -I FORWARD -i ${LAN} -d 192.168.0.0/255.255.0.0 -j DROP</i>
437 # <i>iptables -A FORWARD -i ${LAN} -s 192.168.0.0/255.255.0.0 -j ACCEPT</i>
438 # <i>iptables -A FORWARD -i ${WAN} -d 192.168.0.0/255.255.0.0 -j ACCEPT</i>
439 # <i>iptables -t nat -A POSTROUTING -o ${WAN} -j MASQUERADE</i>
440 <comment>Tell the kernel that ip forwarding is OK</comment>
441 # <i>echo 1 > /proc/sys/net/ipv4/ip_forward</i>
442 # <i>for f in /proc/sys/net/ipv4/conf/*/rp_filter ; do echo 1 > $f ; done</i>
443
444 <comment>This is so when we boot we don't have to run the rules by hand</comment>
445 # <i>/etc/init.d/iptables save</i>
446 # <i>rc-update add iptables default</i>
447 # <i>nano /etc/sysctl.conf</i>
448 <comment>Add/Uncomment the following lines:</comment>
449 net.ipv4.ip_forward = 1
450 net.ipv4.conf.default.rp_filter = 1
451
452 <comment>If you have a dynamic internet address you probably want to enable this:</comment>
453 net.ipv4.ip_dynaddr = 1
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 <p>
462 The ip_dynaddr option is useful for dial on demand systems or when your ISP
463 gives out dynamic addresses. This works around the problem where a connection
464 is attempted before the internet interface is fully setup. Really this just
465 provides for a smoother network experience for users behind your router.
466 </p>
467
468 </body>
469 </section>
470 </chapter>
471
472 <chapter>
473 <title>Fun Things (for a rainy day)</title>
474
475 <section>
476 <title>Intro</title>
477 <body>
478
479 <p>
480 Believe it or not, you're done :). From here on out, I'll cover a bunch of
481 common topics that may interest you. Everything in this chapter is completely
482 optional.
483 </p>
484
485 </body>
486 </section>
487
488 <section>
489 <title>Port Forwarding</title>
490 <body>
491
492 <p>
493 Sometimes you would like to be able to host services on a computer behind the
494 router, or just to make your life easier when connecting remotely. Perhaps you
495 want to run a FTP, HTTP, SSH, or VNC server on one or more machines behind your
496 router and be able to connect to them all. The only caveat is that you can
497 only have one service/machine combo per port. For example, there is no
498 practical way to setup three FTP servers behind your router and then try to
499 connect to them all through port 21; only one can be on port 21 while the
500 others would have to be on say port 123 and port 567.
501 </p>
502
503 <p>
504 All the port forwarding rules are of the form <c>iptables -t nat -A PREROUTING
505 [-p protocol] --dport [external port on router] -i ${WAN} -j DNAT --to [ip/port
506 to forward to]</c>. Unfortunately, iptables does not accept hostnames when port
507 forwarding. If you are forwarding an external port to the same port on the
508 internal machine, you can omit the destination port. See the iptables(8) man
509 page for more information.
510 </p>
511
512 <pre caption="Running the iptables commands">
513 <comment>Copy and paste these examples ...</comment>
514 # <i>export LAN=eth0</i>
515 # <i>export WAN=eth1</i>
516
517 <comment>Forward port 2 to ssh on an internal host</comment>
518 # <i>iptables -t nat -A PREROUTING -p tcp --dport 2 -i ${WAN} -j DNAT --to 192.168.0.2:22</i>
519
520 <comment>FTP forwarding to an internal host</comment>
521 # <i>iptables -t nat -A PREROUTING -p tcp --dport 21 -i ${WAN} -j DNAT --to 192.168.0.56</i>
522
523 <comment>HTTP forwarding to an internal host</comment>
524 # <i>iptables -t nat -A PREROUTING -p tcp --dport 80 -i ${WAN} -j DNAT --to 192.168.0.56</i>
525
526 <comment>VNC forwarding for internal hosts</comment>
527 # <i>iptables -t nat -I PREROUTING -p tcp --dport 5900 -i ${WAN} -j DNAT --to 192.168.0.2</i>
528 # <i>iptables -t nat -I PREROUTING -p tcp --dport 5901 -i ${WAN} -j DNAT --to 192.168.0.3:5900</i>
529 <comment>If you want to VNC in to 192.168.0.3, then just add ':1' to the router's hostname</comment>
530
531 <comment>Bittorrent forwarding</comment>
532 # <i>iptables -t nat -A PREROUTING -p tcp --dport 6881:6889 -i ${WAN} -j DNAT --to 192.168.0.2</i>
533
534 <comment>eDonkey/eMule forwarding</comment>
535 # <i>iptables -t nat -A PREROUTING -p tcp --dport 4662 -i ${WAN} -j DNAT --to 192.168.0.55</i>
536
537 <comment>Game Cube Warp Pipe support</comment>
538 # <i>iptables -t nat -A PREROUTING -p udp --dport 4000 -i ${WAN} -j DNAT --to 192.168.0.56</i>
539
540 <comment>Playstation 2 Online support</comment>
541 # <i>iptables -t nat -A PREROUTING -p tcp --dport 10070:10080 -i ${WAN} -j DNAT --to 192.168.0.11</i>
542 # <i>iptables -t nat -A PREROUTING -p udp --dport 10070:10080 -i ${WAN} -j DNAT --to 192.168.0.11</i>
543
544 <comment>Xbox Live</comment>
545 # <i>iptables -t nat -A PREROUTING -p tcp --dport 3074 -i ${WAN} -j DNAT --to 192.168.0.69</i>
546 # <i>iptables -t nat -A PREROUTING -p udp --dport 3074 -i ${WAN} -j DNAT --to 192.168.0.69</i>
547 # <i>iptables -t nat -A PREROUTING -p udp --dport 88 -i ${WAN} -j DNAT --to 192.168.0.69</i>
548 </pre>
549
550 <note>
551 If you have other common / cool examples, please <mail
552 link="vapier@gentoo.org">e-mail me</mail>.
553 </note>
554
555 </body>
556 </section>
557
558 <section>
559 <title>Identd (for IRC)</title>
560 <body>
561
562 <p>
563 Internet Relay Chat utilizes the ident service pretty heavily. Now that the
564 IRC clients are behind the router, we need a way to host ident for both the
565 router and the clients. One such server has been created called
566 <c>midentd</c>.
567 </p>
568
569 <pre caption="Setting up ident">
570 # <i>emerge midentd</i>
571 # <i>rc-update add midentd default</i>
572 # <i>/etc/init.d/midentd start</i>
573 </pre>
574
575 <p>
576 There are a few other ident servers in portage. Depending on your needs, I
577 would recommend checking out <c>oidentd</c> and <c>fakeidentd</c>.
578 </p>
579
580 </body>
581 </section>
582
583 <!--
584 <section>
585 <title>Traffic Shaping</title>
586 <body>
587 <p>
588 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>
589 found over at the TLDP. Feel free to refer to the original document
590 for more details.
591 </p>
592
593 <p>
594 Here we will be setting up what some people refer to as a "Packet Shaper",
595 <uri link="http://en.wikipedia.org/wiki/Traffic_shaping">"Traffic Shaping"</uri>,
596 or <uri link="http://en.wikipedia.org/wiki/QoS">"Quality of Service"</uri>.
597 Simply put, we want to setup rules on our router that will slow down
598 certain activities (like sending large e-mails or downloading from P2P
599 networks) while keeping other activities (like browsing the web or playing
600 online video games) reasonably fast. A 30 second difference in a video
601 game is a lot worse than a 30 second difference in downloading large
602 files :).
603 </p>
604
605 <p>
606 The first thing is to make sure your kernel has all the features added to
607 it. See the chapter on <uri link="#doc_chap2">Kernel setup</uri> for more
608 information. Next, you will need to <c>emerge iptables iputils</c> so that
609 you will have access to the <c>iptables</c>, <c>ip</c>, and <c>tc</c>
610 commands.
611 </p>
612
613 <p>
614 Before we jump into the commands, let's cover a little of the theory. The
615 way this whole system works is to classify common network streams and then
616 to prioritize them. You use iptables to classify network streams, iputils
617 to define the different priority levels, and the kernel to adjust speeds.
618 Just remember that although you can control outbound traffic pretty tightly
619 (from the LAN to the WAN), your ability to control inbound traffic (from
620 the WAN to the LAN) is somewhat limited. Just remember that the following
621 examples are to get your feet wet; if you want more then I'd suggest
622 reading up on the subject. In this example, we will be using the
623 <uri link="http://luxik.cdi.cz/~devik/qos/htb/">Hierarchical Token Buckets (HTB)</uri>
624 packet scheduling algorithm. Still with me? Great, let's start shaping :).
625 </p>
626
627 <pre caption="Setup">
628 DEV=eth1 <comment>NIC connected to WAN</comment>
629 RATE_OUT=100 <comment>Available outbound bandwidth (in kilobits [kb])</comment>
630 RATE_IN=1400 <comment>Available inbound bandwidth (in kb)</comment>
631
632 <comment>Here we initialize the priority system. The 45 is used to set the default classification level.</comment>
633 ip link set dev ${DEV} qlen 30
634 tc qdisc add dev ${DEV} root handle 1: htb default 45
635 tc class add dev ${DEV} parent 1: classid 1:1 htb rate ${RATE_OUT}kbit
636 </pre>
637
638 <p>
639 Here we initialized the system which will be used to prioritize all of
640 our network traffic. We created our queue, told it to use the HTB
641 algorithm, and set the default classification level to '45'. The
642 default is completely arbitrary, as are the levels we choose from
643 here on out. The only thing that matters is how the levels compare
644 relatively; a level '10' packet will be given preference over a
645 level '45' packet. Let's move on to declaring different levels.
646 </p>
647
648 <pre caption="Declaring levels">
649 tc class add dev $DEV parent 1:1 classid 1:10 htb rate $rkbit ceil $tkbit prio $p
650 tc qdisc add dev $DEV parent 1:10 handle 10: sfq
651 </pre>
652 </body>
653 </section>
654 -->
655
656 <section>
657 <title>Time Server</title>
658 <body>
659
660 <p>
661 Keeping your system time correct is essential in maintaining a healthy system.
662 One of the most common ways of accomplishing this is with the Network Time
663 Protocol (NTP) and the ntp package (which provides implementations for both
664 server and client).
665 </p>
666
667 <p>
668 Many people run ntp clients on their computers. Obviously, the more clients in
669 the world, the larger the load the ntp servers need to shoulder. In
670 environments like home networks though, we can help keep the load down on
671 public servers while still providing the proper time to all our computers. As
672 an added bonus, our private updates will be a lot faster for the clients too!
673 All we have to do is run a ntp server on our router that synchronizes itself
674 with the public internet servers while providing the time to the rest of the
675 computers in the network. To get started, simply <c>emerge ntp</c> on the
676 router.
677 </p>
678
679 <pre caption="Setting up the NTP server">
680 # <i>nano /etc/conf.d/ntp-client</i>
681 <comment>Customize if you wish but the defaults should be fine</comment>
682 # <i>rc-update add ntp-client default</i>
683
684 # <i>nano /etc/ntp.conf</i>
685 <comment>Add the follwing lines:</comment>
686 restrict default ignore
687 restrict 192.168.0.0 mask 255.255.255.0 notrust nomodify notrap
688 <comment>These will allow only ntp clients with an IP
689 address in the 192.168.0.xxx range to use your ntp server</comment>
690 # <i>nano /etc/conf.d/ntpd</i>
691 <comment>Customize if you wish but the defaults should be fine</comment>
692 # <i>rc-update add ntpd default</i>
693
694 # <i>/etc/init.d/ntp-client start</i>
695 # <i>/etc/init.d/ntpd start</i>
696 </pre>
697
698 <note>
699 You should make sure that you allow inbound and outbound communication on the
700 ntp port (123/udp) when setting up the server. The client just needs outbound
701 access on port 123 over udp.
702 </note>
703
704 <p>
705 Now, on your clients, have them <c>emerge ntp</c> also. However, we will just
706 run the ntp client so setup is a lot simpler.
707 </p>
708
709 <pre caption="Setting up a NTP client">
710 # <i>nano /etc/conf.d/ntp-client</i>
711 <comment>Change the 'pool.ntp.org' server in the NTPCLIENT_OPTS variable to '192.168.0.1'</comment>
712 # <i>rc-update add ntp-client default</i>
713 # <i>/etc/init.d/ntp-client start</i>
714 </pre>
715
716 </body>
717 </section>
718
719 <section>
720 <title>Rsync Server</title>
721 <body>
722
723 <p>
724 For those who run multiple Gentoo boxes on the same lan, you often want to
725 keep from having every machine running <c>emerge sync</c> with remote
726 servers. By setting up a local rsync, you save on both your bandwidth and
727 the Gentoo rsync servers' bandwidth. It's pretty simple to do.
728 </p>
729
730 <note>
731 For a much more in-depth rsync guide, please see the official <uri
732 link="/doc/en/rsync.xml#local">rsync guide</uri>.
733 </note>
734
735 <p>
736 Since every Gentoo machine requires rsync, theres no need to emerge it. Edit
737 the default <path>/etc/rsyncd.conf</path> config file, uncomment the
738 <c>[gentoo-portage]</c> section, and make sure you add an <c>address</c>
739 option. All the other defaults should be fine.
740 </p>
741
742 <pre caption="Rsync server config">
743 pid file = /var/run/rsyncd.pid
744 use chroot = yes
745 read only = yes
746 address = 192.168.0.1
747
748 [gentoo-portage]
749 path = /mnt/space/portage
750 comment = Gentoo Linux Portage tree
751 exclude = /distfiles /packages
752 </pre>
753
754 <p>
755 Then you need to start the service (again, the defaults are OK).
756 </p>
757
758 <pre caption="Starting the rsync server">
759 # <i>/etc/init.d/rsyncd start</i>
760 # <i>rc-update add rsyncd default</i>
761 </pre>
762
763 <p>
764 Only thing left is to set tell your clients to sync against the router.
765 </p>
766
767 <pre caption="Client SYNC settings in make.conf">
768 SYNC="rsync://192.168.0.1/gentoo-portage"
769 </pre>
770
771 </body>
772 </section>
773
774 <section>
775 <title>Mail Server</title>
776 <body>
777
778 <p>
779 Sometimes it's nice to run your own Simple Mail Transfer Protocol (SMTP) server
780 on the router. You may have your own reason for wanting to do so, but I run it
781 so that the users see mail as being sent instantly and the work of
782 retrying/routing is left up to the mail server. Some ISPs also don't allow for
783 mail relaying for accounts that aren't part of their network (like Verizon).
784 Also, you can easily throttle the delivery of mail so that large attachments
785 won't seriously lag your connection for half an hour.
786 </p>
787
788 <pre caption="Setting up SMTP">
789 # <i>emerge qmail</i>
790 <comment>make sure the output of `hostname` is correct</comment>
791 # <i>ebuild /var/db/pkg/*-*/qmail-1.03-r*/*.ebuild config</i>
792 # <i>iptables -I INPUT -p tcp --dport smtp -i ! ${LAN} -j REJECT</i>
793 # <i>ln -s /var/qmail/supervise/qmail-send /service/qmail-send</i>
794 # <i>ln -s /var/qmail/supervise/qmail-smtpd /service/qmail-smtpd</i>
795 <!--
796 # <i>cd /etc/tcprules.d</i>
797 # <i>nano tcp.qmail-smtp</i>
798 -->
799 # <i>cd /etc</i>
800 # <i>nano tcp.smtp</i>
801 <comment>Add an entry like so to the allow section:</comment>
802 192.168.0.:allow,RELAYCLIENT=""
803 <!--
804 # <i>tcprules tcp.qmail-qmtp.cdb rules.tmp &lt; tcp.qmail-smtp</i>
805 -->
806 # <i>tcprules tcp.smtp.cdb rules.tmp &lt; tcp.smtp</i>
807 # <i>rc-update add svscan default</i>
808 # <i>/etc/init.d/svscan start</i>
809 </pre>
810
811 <p>
812 I'm a huge fan of qmail, but you're free to use a different mta :). When you
813 setup e-mail on the hosts in your network, tell them that their SMTP server is
814 192.168.0.1 and everything should be peachy. You might want to visit the <uri
815 link="http://qmail.org/">qmail homepage</uri> for more documentation.
816 </p>
817
818 </body>
819 </section>
820
821 <!--
822 <section>
823 <title>E-mail Virus Scanning</title>
824 <body>
825 <p>
826 If you'd like to provide e-mail virus scanning for your users, but
827 don't want to have to install a virus scanner on every single machine,
828 then <c>pop3vscan</c> may just be the thing for you; a transparent
829 Post Office Protocol (POP) scanner.
830 </p>
831
832 <pre caption="Setting up pop3vscan">
833 TODO
834 </pre>
835
836 </body>
837 </section>
838 -->
839
840 <section>
841 <title>Full DHCP Server</title>
842 <body>
843
844 <p>
845 Earlier we used dnsmasq to provide DHCP service to all our clients. For most
846 people with a simple small LAN, this is perfect. But you may need something
847 with more features. Thus we turn to a full-featured DHCP server as provided
848 by the <uri link="http://www.isc.org/products/DHCP">ISC</uri> folks.
849 </p>
850
851 <pre caption="Setting up dhcpd">
852 # <i>emerge dhcp</i>
853 # <i>nano /etc/dhcp/dhcpd.conf</i>
854 <comment>(Here is a sample configuration file:)</comment>
855 authoritative;
856 ddns-update-style interim;
857 subnet 192.168.0.0 netmask 255.255.255.0 {
858 range 192.168.0.100 192.168.0.250;
859 default-lease-time 259200;
860 max-lease-time 518400;
861 option subnet-mask 255.255.255.0;
862 option broadcast-address 192.168.0.255;
863 option routers 192.168.0.1;
864 option domain-name-servers 192.168.0.1;
865 }
866 # <i>nano /etc/conf.d/dhcpd</i>
867 <comment>(Set IFACE="eth0")</comment>
868 # <i>rc-update add dhcpd default</i>
869 # <i>/etc/init.d/dhcpd start</i>
870 </pre>
871
872 <p>
873 This is the minimal setup required to replace the dnsmasq DHCP functionality
874 that we used earlier. Speaking of which, you did remember to disable the DHCP
875 features in dnsmasq didn't you? If not, you should do so now (just comment
876 out the <c>dhcp-range</c> setting in <path>/etc/dnsmasq.conf</path> and restart
877 the service).
878 </p>
879
880 </body>
881 </section>
882
883 <section>
884 <title>Connect Another LAN (or two or three or ...)</title>
885 <body>
886
887 <p>
888 Sometimes you have need of connecting the router to another LAN. Maybe you
889 want to hook up a group of friends temporarily, or you're a neat freak and
890 want to section off different groups of computers, or you're just really
891 really bored. Whatever the reasons, extending the router to other LAN
892 networks should be pretty straightforward. In the following examples, I will
893 assume that this new network is connected via a third ethernet card, namely
894 <c>eth2</c>.
895 </p>
896
897 <p>
898 First you need to configure the interface. Just take the instructions in the
899 <uri link="#doc_chap4_pre1">4.1 code listing</uri> and replace <c>eth0</c>
900 with <c>eth2</c> and <c>192.168.0</c> with <c>192.168.1</c>.
901 </p>
902
903 <p>
904 Then you need to tweak dnsmasq to service the new interface. Just edit the
905 <path>/etc/conf.d/dnsmasq</path> file again and append <c>-i eth2</c> to
906 DNSMASQ_OPTS; using -i multiple times is OK. Then edit
907 <path>/etc/dnsmasq.conf</path> and add another line like the dhcp-range line
908 in the <uri link="#doc_chap5_pre1">5.1 code listing</uri>, replacing
909 <c>192.168.0</c> with <c>192.168.1</c>. Having multiple dhcp-range lines is
910 OK too.
911 </p>
912
913 <p>
914 Finally, see the rules in the <uri link="#doc_chap5_pre2">5.2 code
915 listing</uri> and duplicate the rules that have <c>-i ${LAN}</c> in them. You
916 may want to create another variable, say <c>LAN2</c>, to make things easier.
917 </p>
918
919 </body>
920 </section>
921
922 </chapter>
923
924 <chapter>
925 <title>Troubleshooting</title>
926
927 <section>
928 <title>Useful Tools</title>
929 <body>
930
931 <p>
932 If you're having trouble getting your computers to communicate, you may way to
933 try out the following tools (they can all be found in the <c>net-analyzer</c>
934 portage category):
935 </p>
936
937 <table>
938 <tr>
939 <th>Utility</th>
940 <th>Description</th>
941 </tr>
942 <tr>
943 <ti>ethereal</ti>
944 <ti>GUI tool to view all raw network data according to filters</ti>
945 </tr>
946 <tr>
947 <ti>tcpdump</ti>
948 <ti>Console tool to dump all raw network data according to filters</ti>
949 </tr>
950 <tr>
951 <ti>iptraf</ti>
952 <ti>ncurses based IP LAN monitor</ti>
953 </tr>
954 <tr>
955 <ti>ettercap</ti>
956 <ti>ncurses based network monitor/control</ti>
957 </tr>
958 </table>
959
960 </body>
961 </section>
962
963 <section>
964 <title>DHCP Fails To Start</title>
965 <body>
966
967 <p>
968 When starting the dhcp init.d script for the first time, it may fail to load
969 but neglect to give you any useful info.
970 </p>
971
972 <pre caption="DHCP Failing Example">
973 # <i>/etc/init.d/dhcp start</i>
974 * Setting ownership on dhcp.leases ... [ ok ]
975 * Starting dhcpd ... [ !! ]
976 </pre>
977
978 <p>
979 The trick is to know where dhcpd is sending its output. Simply browse to
980 <path>/var/log</path> and read the log files. Since the exact log file depends
981 on the package you are using as a syslog, try running <c>grep -Rl dhcpd
982 /var/log</c> to narrow down the possibilities. Chances are you made a typo in
983 your config file. You could also try running <c>dhcpd -d -f</c> (short for
984 debug / foreground) and debug the error based upon the output.
985 </p>
986
987 </body>
988 </section>
989
990 <section>
991 <title>Incorrect MTU Value</title>
992 <body>
993
994 <p>
995 If you experience odd errors (such as not being able to access some webpages
996 while others load fine), you may be having Path MTU Discovery trouble. The
997 quick way to test is to run this iptables command:
998 </p>
999
1000 <pre caption="Circumvent MTU issues">
1001 # <i>iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu</i>
1002 </pre>
1003
1004 <p>
1005 This will affect all new connections, so just refresh the website you're
1006 having problems with in order to test. In case it helps, the standard MTU
1007 value for 100mbit ethernet connections is <c>1500</c> while for PPPoE
1008 connections it is <c>1492</c>. For more info, you should read Chapter 15
1009 of the <uri link="http://lartc.org/howto/">Linux Advanced Routing &amp;
1010 Traffic Control HOWTO</uri>.
1011 </p>
1012
1013 </body>
1014 </section>
1015
1016 <section>
1017 <title>Unable to connect two machines directly</title>
1018 <body>
1019
1020 <p>
1021 If (for whatever reason) you want to connect two machines directly together
1022 without a hub or switch, a regular ethernet cable will likely not work, unless
1023 you have an Auto MDI/MDI-X (also known as "autosensing") capable network
1024 adapter. You will need a different cable called a crossover cable. This <uri
1025 link="http://en.wikipedia.org/wiki/Ethernet_crossover_cable">Wikipedia</uri>
1026 page explains the low level details.
1027 </p>
1028
1029 </body>
1030 </section>
1031
1032 </chapter>
1033
1034 <chapter>
1035 <title>Final Notes</title>
1036 <section>
1037 <body>
1038
1039 <p>
1040 I have no final notes other than if you experience any troubles with the guide,
1041 please contact <mail link="vapier@gentoo.org">me</mail> or file a bug with <uri
1042 link="http://bugs.gentoo.org/">Gentoo's Bugtracking Website</uri>. If you have
1043 some interesting bits you think would enhance this guide, by all means send it
1044 my way for inclusion.
1045 </p>
1046
1047 </body>
1048 </section>
1049 </chapter>
1050 </guide>

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