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fixed dhcpcd pros/cons for bug 159610

1 <?xml version="1.0" encoding="UTF-8"?>
2 <!DOCTYPE sections SYSTEM "/dtd/book.dtd">
3
4 <!-- The content of this document is licensed under the CC-BY-SA license -->
5 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
6
7 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-net-modules.xml,v 1.19 2006/10/28 09:17:55 neysx Exp $ -->
8
9 <sections>
10
11 <abstract>
12 Gentoo provides you flexible networking - here you are told about choosing
13 different DHCP clients, setting up bonding, bridging, VLANs and more.
14 </abstract>
15
16 <version>7.1</version>
17 <date>2006-01-04</date>
18
19 <section>
20 <title>Network Modules</title>
21 <body>
22
23 <p>
24 We now support modular networking scripts, which means we can easily add support
25 for new interface types and configuration modules while keeping compatibility
26 with existing ones.
27 </p>
28
29 <p>
30 Modules load by default if the package they need is installed. If you specify a
31 module here that doesn't have its package installed then you get an error
32 stating which package you need to install. Ideally, you only use the modules
33 setting when you have two or more packages installed that supply the same
34 service and you need to prefer one over the other.
35 </p>
36
37 <note>
38 All settings discussed here are stored in <path>/etc/conf.d/net</path> unless
39 otherwise specified.
40 </note>
41
42 <pre caption="Module preference">
43 <comment># Prefer iproute2 over ifconfig</comment>
44 modules=( "iproute2" )
45
46 <comment># You can also specify other modules for an interface
47 # In this case we prefer udhcpc over dhcpcd</comment>
48 modules_eth0=( "udhcpc" )
49
50 <comment># You can also specify which modules not to use - for example you may be
51 # using a supplicant or linux-wlan-ng to control wireless configuration but
52 # you still want to configure network settings per ESSID associated with.</comment>
53 modules=( "!iwconfig" )
54 </pre>
55
56 </body>
57 </section>
58 <section>
59 <title>Interface Handlers</title>
60 <body>
61
62 <p>
63 We provide two interface handlers presently: <c>ifconfig</c> and
64 <c>iproute2</c>. You need one of these to do any kind of network configuration.
65 </p>
66
67 <p>
68 <c>ifconfig</c> is the current Gentoo default and it's included in the system
69 profile. <c>iproute2</c> is a more powerful and flexible package, but it's not
70 included by default.
71 </p>
72
73 <pre caption="To install iproute2">
74 # <i>emerge sys-apps/iproute2</i>
75
76 <comment># To prefer iproute2 over ifconfig if both are installed</comment>
77 modules=( "iproute2" )
78 </pre>
79
80 <p>
81 As both <c>ifconfig</c> and <c>iproute2</c> do very similar things we allow
82 their basic configuration to work with each other. For example both the below
83 code snippet work regardless of which module you are using.
84 </p>
85
86 <pre caption="ifconfig and iproute2 examples">
87 config_eth0=( "192.168.0.2/24" )
88 config_eth0=( "192.168.0.2 netmask 255.255.255.0" )
89
90 <comment># We can also specify broadcast</comment>
91 config_eth0=( "192.168.0.2/24 brd 192.168.0.255" )
92 config_eth0=( "192.168.0.2 netmask 255.255.255.0 broadcast 192.168.0.255" )
93 </pre>
94
95 </body>
96 </section>
97 <section id="dhcp">
98 <title>DHCP</title>
99 <body>
100
101 <p>
102 DHCP is a means of obtaining network information (IP address, DNS servers,
103 Gateway, etc) from a DHCP server. This means that if there is a DHCP server
104 running on the network, you just have to tell each client to use DHCP and it
105 sets up the network all by itself. Of course, you will have to configure for
106 other things like wireless, PPP or other things if required before you can use
107 DHCP.
108 </p>
109
110 <p>
111 DHCP can be provided by <c>dhclient</c>, <c>dhcpcd</c>, <c>pump</c> or
112 <c>udhcpc</c>. Each DHCP module has its pros and cons - here's a quick run down.
113 </p>
114
115 <table>
116 <tr>
117 <th>DHCP Module</th>
118 <th>Package</th>
119 <th>Pros</th>
120 <th>Cons</th>
121 </tr>
122 <tr>
123 <ti><c>dhclient</c></ti>
124 <ti><c>net-misc/dhcp</c></ti>
125 <ti>
126 Made by ISC, the same people who make the BIND DNS software. Very
127 configurable
128 </ti>
129 <ti>
130 Configuration is overly complex, software is quite bloated, cannot get
131 NTP servers from DHCP, does not send hostname by default
132 </ti>
133 </tr>
134 <tr>
135 <ti><c>dhcpcd</c></ti>
136 <ti><c>net-misc/dhcpcd</c></ti>
137 <ti>
138 Long time Gentoo default, no reliance on outside tools, actively developed
139 by Gentoo
140 </ti>
141 <ti>Can be slow at times, does not yet daemonize when lease is infinite</ti>
142 </tr>
143 <tr>
144 <ti><c>pump</c></ti>
145 <ti><c>net-misc/pump</c></ti>
146 <ti>
147 Lightweight, no reliance on outside tools
148 </ti>
149 <ti>
150 No longer maintained upstream, unreliable, especially over modems, cannot
151 get NIS servers from DHCP
152 </ti>
153 </tr>
154 <tr>
155 <ti><c>udhcpc</c></ti>
156 <ti><c>net-misc/udhcp</c></ti>
157 <ti>
158 Lightweight - smallest DHCP client around, made for embedded systems
159 </ti>
160 <ti>
161 Unproven - no distro uses it by default, cannot define a timeout beyond 3
162 seconds
163 </ti>
164 </tr>
165 </table>
166
167 <p>
168 If you have more than one DHCP client installed, you need to specify which one
169 to use - otherwise we default to <c>dhcpcd</c> if available.
170 </p>
171
172 <p>
173 To send specific options to the DHCP module, use <c>module_eth0="..."</c>
174 <e>(change module to the DHCP module you're using - i.e. <c>dhcpcd_eth0</c>)</e>.
175 </p>
176
177 <p>
178 We try and make DHCP relatively agnostic - as such we support the following
179 commands using the <c>dhcp_eth0</c> variable. The default is not to set any of
180 them:
181 </p>
182
183 <ul>
184 <li><c>release</c> - releases the IP address for re-use</li>
185 <li><c>nodns</c> - don't overwrite <path>/etc/resolv.conf</path></li>
186 <li><c>nontp</c> - don't overwrite <path>/etc/ntp.conf</path></li>
187 <li><c>nonis</c> - don't overwrite <path>/etc/yp.conf</path></li>
188 </ul>
189
190 <pre caption="Sample DHCP configuration in /etc/conf.d/net">
191 <comment># Only needed if you have more than one DHCP module installed</comment>
192 modules=( "dhcpcd" )
193
194 config_eth0=( "dhcp" )
195 dhcpcd_eth0="-t 10" <comment># Timeout after 10 seconds</comment>
196 dhcp_eth0="release nodns nontp nonis" <comment># Only get an address</comment>
197 </pre>
198
199 <note>
200 <c>dhcpcd</c>, <c>udhcpc</c> and <c>pump</c> send the current hostname to the
201 DHCP server by default so you don't need to specify this anymore.
202 </note>
203
204 </body>
205 </section>
206 <section>
207 <title>ADSL Modem</title>
208 <body>
209
210 <p>
211 First we need to install the ADSL software.
212 </p>
213
214 <pre caption="Install the rp-pppoe package">
215 # <i>emerge net-dialup/rp-pppoe</i>
216 </pre>
217
218 <warn>
219 <c>baselayout-1.11.x</c> supports PPPoE only. Hopefully future versions will
220 support PPPoA.
221 </warn>
222
223 <p>
224 Now we need to configure <c>eth0</c> to be an ADSL interface and enter our
225 username by updating <path>/etc/conf.d/net</path>.
226 </p>
227
228 <pre caption="Configure eth0 for ADSL in /etc/conf.d/net">
229 config_eth0=( "adsl" )
230 adsl_user_eth0="username"
231 </pre>
232
233 <p>
234 Finally you need to define your username and password in
235 <path>/etc/ppp/pap-secrets</path>.
236 </p>
237
238 <pre caption="sample /etc/ppp/pap-secrets">
239 <comment># The * is important</comment>
240 "username" * "password"
241 </pre>
242
243 </body>
244 </section>
245 <section id="apipa">
246 <title>APIPA (Automatic Private IP Addressing)</title>
247 <body>
248
249 <p>
250 APIPA tries to find a free address in the range 169.254.0.0-169.254.255.255 by
251 arping a random address in that range on the interface. If no reply is found
252 then we assign that address to the interface.
253 </p>
254
255 <p>
256 This is only useful for LANs where there is no DHCP server and you don't connect
257 directly to the internet and all other computers use APIPA.
258 </p>
259
260 <p>
261 For APIPA support, emerge <c>net-misc/iputils</c> or <c>net-analyzer/arping</c>.
262 </p>
263
264 <pre caption="APIPA configuration in /etc/conf.d/net">
265 <comment># Try DHCP first - if that fails then fallback to APIPA</comment>
266 config_eth0=( "dhcp" )
267 fallback_eth0=( "apipa" )
268
269 <comment># Just use APIPA</comment>
270 config_eth0=( "apipa" )
271 </pre>
272
273 </body>
274 </section>
275 <section>
276 <title>Bonding</title>
277 <body>
278
279 <p>
280 For link bonding/trunking emerge <c>net-misc/ifenslave</c>.
281 </p>
282
283 <p>
284 Bonding is used to increase network bandwidth. If you have two network cards
285 going to the same network, you can bond them together so your applications see
286 just one interface but they really use both network cards.
287 </p>
288
289 <pre caption="bonding configuration in /etc/conf.d/net">
290 <comment># To bond interfaces together</comment>
291 slaves_bond0="eth0 eth1 eth2"
292
293 <comment># You may not want to assign an IP to the bonded interface</comment>
294 config_bond0=( "null" )
295
296 <comment># Depend on eth0, eth1 and eth2 as they may require extra configuration</comment>
297 depend_bond0() {
298 need net.eth0 net.eth1 net.eth2
299 }
300 </pre>
301
302 </body>
303 </section>
304 <section>
305 <title>Bridging (802.1d support)</title>
306 <body>
307
308 <p>
309 For bridging support emerge <c>net-misc/bridge-utils</c>.
310 </p>
311
312 <p>
313 Bridging is used to join networks together. For example, you may have a server
314 that connects to the internet via an ADSL modem and a wireless access card to
315 enable other computers to connect to the internet via the ADSL modem. You could
316 create a bridge to join the two interfaces together.
317 </p>
318
319 <pre caption="Bridge configuration in /etc/conf.d/net">
320 <comment># Configure the bridge - "man btctl" for more details</comment>
321 brctl_br0=( "setfd 0" "sethello 0" "stp off" )
322
323 <comment># To add ports to bridge br0</comment>
324 bridge_br0="eth0 eth1"
325
326 <comment># You need to configure the ports to null values so dhcp does not get started</comment>
327 config_eth0=( "null" )
328 config_eth1=( "null" )
329
330 <comment># Finally give the bridge an address - you could use DHCP as well</comment>
331 config_br0=( "192.168.0.1/24" )
332
333 <comment># Depend on eth0 and eth1 as they may require extra configuration</comment>
334 depend_br0() {
335 need net.eth0 net.eth1
336 }
337 </pre>
338
339 <impo>
340 For using some bridge setups, you may need to consult the <uri
341 link="?part=4&amp;chap=2#variable_name">variable name</uri> documentation.
342 </impo>
343
344 </body>
345 </section>
346 <section>
347 <title>MAC Address</title>
348 <body>
349
350 <p>
351 You don't need to emerge anything for changing the MAC address of your
352 interface if you have <c>sys-apps/baselayout-1.11.14</c> or newer and want to
353 change to a specific MAC address. However, if you need to change to a random MAC
354 address or have a baselayout older than the version mentioned above, you have
355 to emerge <c>net-analyzer/macchanger</c> to be able to make use of this feature.
356 </p>
357
358 <pre caption="MAC Address change example">
359 <comment># To set the MAC address of the interface</comment>
360 mac_eth0="00:11:22:33:44:55"
361
362 <comment># To randomize the last 3 bytes only</comment>
363 mac_eth0="random-ending"
364
365 <comment># To randomize between the same physical type of connection (e.g. fibre,
366 # copper, wireless) , all vendors</comment>
367 mac_eth0="random-samekind"
368
369 <comment># To randomize between any physical type of connection (e.g. fibre, copper,
370 # wireless) , all vendors</comment>
371 mac_eth0="random-anykind"
372
373 <comment># Full randomization - WARNING: some MAC addresses generated by this may
374 # NOT act as expected</comment>
375 mac_eth0="random-full"
376 </pre>
377
378 </body>
379 </section>
380 <section>
381 <title>Tunnelling</title>
382 <body>
383
384 <p>
385 You don't need to emerge anything for tunnelling as the interface handler can do
386 it for you.
387 </p>
388
389 <pre caption="Tunnelling configuration in /etc/conf.d/net">
390 <comment># For GRE tunnels</comment>
391 iptunnel_vpn0="mode gre remote 207.170.82.1 key 0xffffffff ttl 255"
392
393 <comment># For IPIP tunnels</comment>
394 iptunnel_vpn0="mode ipip remote 207.170.82.2 ttl 255"
395
396 <comment># To configure the interface</comment>
397 config_vpn0=( "192.168.0.2 peer 192.168.1.1" )
398 </pre>
399
400 </body>
401 </section>
402 <section>
403 <title>VLAN (802.1q support)</title>
404 <body>
405
406 <p>
407 For VLAN support, emerge <c>net-misc/vconfig</c>.
408 </p>
409
410 <p>
411 Virtual LAN is a group of network devices that behave as if they were connected
412 to a single network segment - even though they may not be. VLAN members can only
413 see members of the same VLAN even though they may share the same physical
414 network.
415 </p>
416
417 <pre caption="VLAN configuration in /etc/conf.d/net">
418 <comment># Specify the VLAN numbers for the interface like so</comment>
419 <comment># Please ensure your VLAN IDs are NOT zero-padded</comment>
420 vlans_eth0="1 2"
421
422 <comment># You can also configure the VLAN</comment>
423 <comment># see for vconfig man page for more details</comment>
424 vconfig_eth0=( "set_name_type VLAN_PLUS_VID_NO_PAD" )
425 vconfig_vlan1=( "set_flag 1" "set_egress_map 2 6" )
426
427 <comment># Configure the interface as usual</comment>
428 config_vlan1=( "172.16.3.1 netmask 255.255.254.0" )
429 config_vlan2=( "172.16.2.1 netmask 255.255.254.0" )
430 </pre>
431
432 <impo>
433 For using some VLAN setups, you may need to consult the <uri
434 link="?part=4&amp;chap=2#variable_name">variable name</uri> documentation.
435 </impo>
436
437 </body>
438 </section>
439
440 </sections>

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