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25 <H1>L2TPNS Manual</H1>
26 <OL>
27 <LI><A HREF="#Overview">Overview</A></LI>
28 <LI><A HREF="#Installation">Installation</A>
29 <OL>
30 <LI><A HREF="#Requirements">Requirements</A></LI>
31 <LI><A HREF="#Compile">Compile</A></LI>
32 <LI><A HREF="#Install">Install</A></LI>
33 <LI><A HREF="#Running">Running</A></LI>
34 </OL>
35 </LI>
36 <LI><A HREF="#Configuration">Configuration</A>
37 <OL>
38 <LI><A HREF="#startup-config">startup-config</A></LI>
39 <LI><A HREF="#users">users</A></LI>
40 <LI><A HREF="#ip-pool">ip_pool</A></LI>
41 <LI><A HREF="#build-garden">build-garden</A></LI>
42 </OL>
43 </LI>
44 <LI><A HREF="#ControllingtheProcess">Controlling the Process</A>
45 <OL>
46 <LI><A HREF="#Command-LineInterface">Command-Line Interface</A></LI>
47 <LI><A HREF="#nsctl">nsctl</A></LI>
48 <LI><A HREF="#Signals">Signals</A></LI>
49 </OL>
50 </LI>
51 <LI><A HREF="#Throttling">Throttling</A></LI>
52 <LI><A HREF="#Interception">Interception</A></LI>
53 <LI><A HREF="#Authentication">Authentication</A></LI>
54 <LI><A HREF="#Plugins">Plugins</A></LI>
55 <LI><A HREF="#WalledGarden">Walled Garden</A></LI>
56 <LI><A HREF="#Filtering">Filtering</A></LI>
57 <LI><A HREF="#Clustering">Clustering</A></LI>
58 <LI><A HREF="#Routing">Routing</A></LI>
59 <LI><A HREF="#Performance">Performance</A></LI>
60 </OL>
61
62 <H2 ID="Overview">Overview</H2>
63 l2tpns a complete L2TP implementation. It supports the LAC, LNS and
64 PPPOE server.<P>
65
66 L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer 2
67 protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection. l2tpns
68 implements PPP over L2TP only.<P>
69
70 There are a couple of other L2TP implementations, of which <A
71 HREF="http://sourceforge.net/projects/l2tpd">l2tpd</A> is probably the
72 most popular. l2tpd also will handle being either end of a tunnel, and
73 is a lot more configurable than l2tpns. However, due to the way it works,
74 it is nowhere near as scalable.<P>
75
76 l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive
77 and send packets. Using some packet manipulation it doesn't require a
78 single interface per connection, as l2tpd does.<P>
79
80 This allows it to scale extremely well to very high loads and very high
81 numbers of connections.<P>
82
83 It also has a plugin architecture which allows custom code to be run
84 during processing. An example of this is in the walled garden module
85 included.<P>
86
87 <BR>
88 <EM>Documentation is not my best skill. If you find any problems
89 with this document, or if you wish to contribute, please email <A
90 HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list</A>.</EM><P>
91
92 <H2 ID="Installation">Installation</H2>
93 <H3 ID="Requirements">Requirements</H3>
94
95 <OL>
96 <LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
97 compiled in, or as a module.</LI>
98
99 <LI>libcli 1.8.0 or greater.<BR>You can get this from <A
100 HREF="http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli</A></LI>
101 </OL>
102
103 <H3 ID="Compile">Compile</H3>
104
105 You can generally get away with just running <B>make</B> from the source
106 directory. This will compile the daemon, associated tools and any modules
107 shipped with the distribution.<P>
108
109 <H3 ID="Install">Install</H3>
110
111 After you have successfully compiled everything, run <B>make
112 install</B> to install it. By default, the binaries are installed into
113 <EM>/usr/sbin</EM>, the configuration into <EM>/etc/l2tpns</EM>, and the
114 modules into <EM>/usr/lib/l2tpns</EM>.<P>
115
116 You will definately need to edit the configuration files before you
117 start. See the <A HREF="#Configuration">Configuration</A> section for
118 more information.<P>
119
120 <H3 ID="Running">Running</H3>
121
122 You only need to run <B>/usr/sbin/l2tpns</B> as root to start it. It does
123 not detach to a daemon process, so you should perhaps run it from init.<P>
124
125 By default there is no log destination set, so all log messages will go to
126 stdout.<P>
127
128 <H2 ID="Configuration">Configuration</H2>
129
130 All configuration of the software is done from the files installed into
131 /etc/l2tpns.
132
133 <H3 ID="startup-config">startup-config</H3>
134
135 This is the main configuration file for l2tpns. The format of the file is a
136 list of commands that can be run through the command-line interface. This
137 file can also be written directly by the l2tpns process if a user runs the
138 <EM>write memory</EM> command, so any comments will be lost. However if your
139 policy is not to write the config by the program, then feel free to comment
140 the file with a # or ! at the beginning of the line.<P>
141
142 A list of the possible configuration directives follows. Each of these
143 should be set by a line like:<P>
144 <PRE>
145 set configstring "value"
146 set ipaddress 192.168.1.1
147 set boolean true
148 </PRE>
149
150 <P>
151 <UL>
152 <LI><B>debug</B> (int)<BR>
153 Sets the level of messages that will be written to the log file. The value
154 should be between 0 and 5, with 0 being no debugging, and 5 being the
155 highest. A rough description of the levels is:
156 <OL>
157 <LI VALUE=0>Critical Errors - Things are probably broken</LI>
158 <LI>Errors - Things might have gone wrong, but probably will recover</LI>
159 <LI>Warnings - Just in case you care what is not quite perfect</LI>
160 <LI>Information - Parameters of control packets</LI>
161 <LI>Calls - For tracing the execution of the code</LI>
162 <LI>Packets - Everything, including a hex dump of all packets processed... probably twice</LI>
163 </OL><P>
164 Note that the higher you set the debugging level, the slower the program
165 will run. Also, at level 5 a LOT of information will be logged. This should
166 only ever be used for working out why it doesn't work at all.
167 </LI>
168
169 <LI><B>log_file</B> (string)<BR>
170 This will be where all logging and debugging information is written
171 to. This may be either a filename, such as <EM>/var/log/l2tpns</EM>, or
172 the special magic string <EM>syslog:facility</EM>, where <EM>facility</EM>
173 is any one of the syslog logging facilities, such as local5.
174 </LI>
175
176 <LI><B>pid_file</B> (string)<BR>
177 If set, the process id will be written to the specified file. The
178 value must be an absolute path.
179 </LI>
180
181 <LI><B>l2tp_secret</B> (string)<BR>
182 The secret used by l2tpns for authenticating tunnel request. Must be
183 the same as the LAC, or authentication will fail. Only actually be
184 used if the LAC requests authentication.
185 </LI>
186
187 <LI><B>l2tp_mtu</B> (int)<BR>
188 MTU of interface for L2TP traffic (default: 1500). Used to set link
189 MRU and adjust TCP MSS.
190 </LI>
191
192 <LI><B>ppp_restart_time</B> (int)<BR>
193 <B>ppp_max_configure</B> (int)<BR>
194 <B>ppp_max_failure</B> (int)<BR>
195 PPP counter and timer values, as described in &sect;4.1 of
196 <a href="ftp://ftp.rfc-editor.org/in-notes/rfc1661.txt">RFC1661</a>.
197 </LI>
198
199 <LI><B>primary_dns</B> (ip address)
200 <LI><B>secondary_dns</B> (ip address)<BR>
201 Whenever a PPP connection is established, DNS servers will be sent to the
202 user, both a primary and a secondary. If either is set to 0.0.0.0, then that
203 one will not be sent.
204 </LI>
205
206 <LI><B>primary_radius</B> (ip address)
207 <LI><B>secondary_radius</B> (ip address)<BR>
208 Sets the RADIUS servers used for both authentication and accounting.
209 If the primary server does not respond, then the secondary RADIUS
210 server will be tried.<br>
211 <strong>Note:</strong> in addition to the source IP address and
212 identifier, the RADIUS server <strong>must</strong> include the source
213 port when detecting duplicates to supress (in order to cope with a
214 large number of sessions comming on-line simultaneously l2tpns uses a
215 set of udp sockets, each with a seperate identifier).
216 </LI>
217
218 <LI><B>primary_radius_port</B> (short)
219 <LI><B>secondary_radius_port</B> (short)<BR>
220 Sets the authentication ports for the primary and secondary RADIUS
221 servers. The accounting port is one more than the authentication
222 port. If no RADIUS ports are given, the authentication port defaults
223 to 1645, and the accounting port to 1646.
224 </LI>
225
226 <LI><B>radius_accounting</B> (boolean)<BR>
227 If set to true, then RADIUS accounting packets will be sent. This
228 means that a Start record will be sent when the session is
229 successfully authenticated, and a Stop record will be sent when the
230 session is closed.
231 </LI>
232
233 <LI><B>radius_secret</B> (string)<BR>
234 This secret will be used in all RADIUS queries. If this is not set then
235 RADIUS queries will fail.
236 </LI>
237
238 <LI><B>radius_authtypes</B> (string)</BR>
239 A comma separated list of supported RADIUS authentication methods
240 (<B>pap</B> or <B>chap</B>), in order of preference (default <B>pap</B>).
241 </LI>
242
243 <LI><B>radius_dae_port</B> (short)<BR>
244 Port for DAE RADIUS (Packet of Death/Disconnect, Change of Authorization)
245 requests (default: <B>3799</B>).
246 </LI>
247
248 <LI><B>allow_duplicate_users</B> (boolean)</BR>
249 Allow multiple logins with the same username. If false (the default),
250 any prior session with the same username will be dropped when a new
251 session is established.
252 </LI>
253
254 <LI><B>bind_address</B> (ip address)<BR>
255 It's the listen address of the l2tp udp protocol sent and received
256 to LAC. This address is also assigned to the tun interface if no
257 iftun_address is specified. Packets containing user traffic should be
258 routed via this address if given, otherwise the primary address of the
259 machine.
260 </LI>
261
262 <LI><B>iftun_address</B> (ip address)<BR>
263 This parameter is used when you want a tun interface address different
264 from the address of "bind_address" (For use in cases of specific configuration).
265 If no address is given to iftun_address and bind_address, 1.1.1.1 is used.
266 </LI>
267
268 <LI><B>bind_multi_address</B> (ip address)<BR>
269 This parameter permit to listen several addresss of the l2tp udp protocol
270 (and set several address to the tun interface).
271 <BR>
272 WHEN this parameter is set, It OVERWRITE the parameters "bind_address"
273 and "iftun_address".
274 <BR>
275 these can be interesting when you want do load-balancing in cluster mode
276 of the uploaded from the LAC. For example you can set a bgp.prepend(MY_AS)
277 for Address1 on LNS1 and a bgp.prepend(MY_AS) for Address2 on LNS2
278 (see BGP AS-path prepending).
279 <BR>
280 example of use with 2 address:
281 <BR>
282 set bind_multi_address "64.14.13.41, 64.14.13.42"
283
284 </LI>
285
286 <LI><B>tundevicename</B> (string)<BR>
287 Name of the tun interface (default: "tun0").
288 </LI>
289
290 <LI><B>peer_address</B> (ip address)<BR>
291 Address to send to clients as the default gateway.
292 </LI>
293
294 <LI><B>send_garp</B> (boolean)<BR>
295 Determines whether or not to send a gratuitous ARP for the
296 bind_address when the server is ready to handle traffic (default:
297 true).<BR>
298 This value is ignored if BGP is configured.
299 </LI>
300
301 <LI><B>throttle_speed</B> (int)<BR>
302 Sets the default speed (in kbits/s) which sessions will be limited to.
303 If this is set to 0, then throttling will not be used at all. Note:
304 You can set this by the CLI, but changes will not affect currently
305 connected users.
306 </LI>
307
308 <LI><B>throttle_buckets</B> (int)<BR>
309 Number of token buckets to allocate for throttling. Each throttled
310 session requires two buckets (in and out).
311 </LI>
312
313 <LI><B>accounting_dir</B> (string)<BR>
314 If set to a directory, then every 5 minutes the current usage for
315 every connected use will be dumped to a file in this directory. Each
316 file dumped begins with a header, where each line is prefixed by #.
317 Following the header is a single line for every connected user, fields
318 separated by a space.<BR> The fields are username, ip, qos,
319 uptxoctets, downrxoctets. The qos field is 1 if a standard user, and
320 2 if the user is throttled.
321 </LI>
322
323 <LI><B>setuid</B> (int)<BR>
324 After starting up and binding the interface, change UID to this. This
325 doesn't work properly.
326 </LI>
327
328 <LI><B>dump_speed</B> (boolean)<BR>
329 If set to true, then the current bandwidth utilization will be logged every
330 second. Even if this is disabled, you can see this information by running
331 the <EM>uptime</EM> command on the CLI.
332 </LI>
333
334 <LI><B>multi_read_count</B> (int)<BR>
335 Number of packets to read off each of the UDP and TUN fds when
336 returned as readable by select (default: 10). Avoids incurring the
337 unnecessary system call overhead of select on busy servers.
338 </LI>
339
340 <LI><B>scheduler_fifo</B> (boolean)<BR>
341 Sets the scheduling policy for the l2tpns process to SCHED_FIFO. This
342 causes the kernel to immediately preempt any currently running SCHED_OTHER
343 (normal) process in favour of l2tpns when it becomes runnable.
344 Ignored on uniprocessor systems.
345 </LI>
346
347 <LI><B>lock_pages</B> (boolean)<BR>
348 Keep all pages mapped by the l2tpns process in memory.
349 </LI>
350
351 <LI><B>icmp_rate</B> (int)<BR>
352 Maximum number of host unreachable ICMP packets to send per second.
353 </LI>
354
355 <LI><B>packet_limit</B> (int><BR>
356 Maximum number of packets of downstream traffic to be handled each
357 tenth of a second per session. If zero, no limit is applied (default:
358 0). Intended as a DoS prevention mechanism and not a general
359 throttling control (packets are dropped, not queued).
360 </LI>
361
362 <LI><B>cluster_address</B> (ip address)<BR>
363 Multicast cluster address (default: 239.192.13.13). See the section
364 on <A HREF="#Clustering">Clustering</A> for more information.
365 </LI>
366
367 <LI><B>cluster_interface</B> (string)<BR>
368 Interface for cluster packets (default: eth0).
369 </LI>
370
371 <LI><B>cluster_mcast_ttl</B> (int)<BR>
372 TTL for multicast packets (default: 1).
373 </LI>
374
375 <LI><B>cluster_hb_interval</B> (int)<BR>
376 Interval in tenths of a second between cluster heartbeat/pings.
377 </LI>
378
379 <LI><B>cluster_hb_timeout</B> (int)<BR>
380 Cluster heartbeat timeout in tenths of a second. A new master will be
381 elected when this interval has been passed without seeing a heartbeat
382 from the master.
383 </LI>
384
385 <LI><B>cluster_master_min_adv</B> (int)<BR>
386 Determines the minumum number of up to date slaves required before the
387 master will drop routes (default: 1).
388 </LI>
389
390 <LI><B>echo_timeout</B> (int)<BR>
391 Time between last packet sent and LCP ECHO generation
392 (default: 10 (seconds)).
393 </LI>
394
395 <LI><B>idle_echo_timeout</B> (int)<BR>
396 Drop sessions who have not responded within idle_echo_timeout seconds
397 (default: 240 (seconds))
398 </LI>
399
400 <LI><B>auth_tunnel_change_addr_src</B> (boolean)<BR>
401 This parameter authorize to change the source IP of the tunnels l2tp.
402 This parameter can be used when the remotes BAS/LAC are l2tpns server
403 configured in cluster mode, but that the interface to remote LNS are
404 not clustered (the tunnel can be coming from different source IP)
405 (default: no).
406 </LI>
407
408 <LI><B>disable_sending_hello</B> (boolean)<BR>
409 Disable l2tp sending HELLO message for Apple compatibility.
410 Some OS X implementation of l2tp no manage the L2TP "HELLO message".
411 (default: no).
412 </LI>
413
414 </UL>
415
416 <P><U><B>LAC configuration</B></U></P>
417 <UL>
418 <LI><B>bind_address_remotelns</B> (ip address)<BR>
419 Address of the interface to listen the remote LNS tunnels.
420 If no address is given, all interfaces are listened (Any Address).
421 </LI>
422
423 <LI><B>bind_portremotelns</B> (short)<BR>
424 Port to bind for the Remote LNS (default: 65432).
425 </LI>
426
427 </UL>
428
429 <P>A static REMOTES LNS configuration can be entered by the command:</P>
430 <DL> <DD><B>setforward</B> <I>MASK</I> <I>IP</I> <I>PORT</I> <I>SECRET</I> </DL>
431
432 where <I>MASK</I> specifies the mask of users who have forwarded to
433 remote LNS (ex: "/friendISP@company.com").</BR>
434 where <I>IP</I> specifies the IP of the remote LNS (ex: "66.66.66.55").</BR>
435 where <I>PORT</I> specifies the L2TP Port of the remote LNS
436 (Normally should be 1701) (ex: 1701).</BR>
437 where <I>SECRET</I> specifies the secret password the remote LNS (ex: mysecret).</BR>
438 </BR>
439 The static Remote LNS configuration can be used when the friend ISP not
440 have a proxied Radius.</BR>
441 If the proxied Radius is used, It will return the RADIUS attributes:</BR>
442 Tunnel-Type: 1 = L2TP</BR>
443 Tunnel-Medium-Type: 1 = IPv4</BR>
444 Tunnel-Password: 1 = "LESECRETL2TP"</BR>
445 Tunnel-Server-Endpoint: 1 = "88.xx.xx.x1"</BR>
446 Tunnel-Assignment-Id: 1 = "friendisp_lns1"</BR>
447 Tunnel-Type: 2 = L2TP</BR>
448 Tunnel-Medium-Type: 2 = IPv4</BR>
449 Tunnel-Password: 2 = "LESECRETL2TP"</BR>
450 Tunnel-Server-Endpoint: 2 = "88.xx.xx.x2"</BR>
451 Tunnel-Assignment-Id: 2 = "friendisp_lns2"</BR>
452
453 <P><U><B>PPPOE configuration</B></U></P>
454
455 <UL>
456 <LI><B>pppoe_if_to_bind</B> (string)<BR>
457 PPPOE server interface to bind (ex: "eth0.12"), If not specified the server PPPOE is not enabled.
458 For the pppoe clustering, all the interfaces PPPOE of the clusters must use the same HW address (MAC address).
459 </LI>
460
461 <LI><B>pppoe_service_name</B> (string)<BR>
462 PPPOE service name (default: NULL).
463 </LI>
464
465 <LI><B>pppoe_ac_name</B> (string)<BR>
466 PPPOE access concentrator name (default: "l2tpns-pppoe").
467 </LI>
468
469 <LI><B>pppoe_only_equal_svc_name</B> (boolean)<BR>
470 If set to yes, the PPPOE server only accepts clients with a "service-name"
471 different from NULL and a "service-name" equal to server "service-name" (default: no).
472 </LI>
473
474 </UL>
475
476 <P><U><B>BGP configuration</B></U></P>
477
478 <P>BGP routing configuration is entered by the command:
479 The routing configuration section is entered by the command
480 <DL><DD><B>router bgp</B> <I>as</I></DL>
481 where <I>as</I> specifies the local AS number.
482
483 <P>Subsequent lines prefixed with
484 <DL><DD><B>neighbour</B> <I>peer</I></DL>
485 define the attributes of BGP neighhbours. Valid commands are:
486 <DL>
487 <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
488 <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
489 </DL>
490
491 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
492 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
493 <I>hold</I> are the timer values in seconds.
494
495 <P>Named access-lists are configured using one of the commands:
496 <DL>
497 <DD><B>ip access-list standard</B> <I>name</I>
498 <DD><B>ip access-list extended</B> <I>name</I>
499 </DL>
500
501 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
502 define the body of the access-list. Standard access-list syntax:
503 <DL>
504 <DD>{<B>permit</B>|<B>deny</B>}
505 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
506 [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
507 </DL>
508
509 Extended access-lists:
510
511 <DIV STYLE="margin-left: 4em; text-indent: -2em">
512 <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
513 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
514 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
515 <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
516 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
517 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
518 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
519 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
520 [<B>fragments</B>]
521 <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
522 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
523 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
524 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
525 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
526 [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
527 {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
528 ...|<B>fragments</B>]
529 </DIV>
530
531 <H3 ID="users">users</H3>
532
533 Usernames and passwords for the command-line interface are stored in
534 this file. The format is <I>username</I><B>:</B><I>password</I> where
535 <I>password</I> may either by plain text, an MD5 digest (prefixed by
536 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
537 plain text by the prefix <B>{crypt}</B>.<P>
538
539 The username <B>enable</B> has a special meaning and is used to set
540 the enable password.<P>
541
542 <B>Note:</B> If this file doesn't exist, then anyone who can get to
543 port 23 will be allowed access without a username / password.<P>
544
545 <H3 ID="ip-pool">ip_pool</H3>
546
547 This file is used to configure the IP address pool which user
548 addresses are assigned from. This file should contain either an IP
549 address or a CIDR network per line. e.g.:<P>
550
551 <PRE>
552 192.168.1.1
553 192.168.1.2
554 192.168.1.3
555 192.168.4.0/24
556 172.16.0.0/16
557 10.0.0.0/8
558 </PRE>
559
560 Keep in mind that l2tpns can only handle 65535 connections per
561 process, so don't put more than 65535 IP addresses in the
562 configuration file. They will be wasted.
563
564 <H3 ID="build-garden">build-garden</H3>
565
566 The garden plugin on startup creates a NAT table called "garden" then
567 sources the <B>build-garden</B> script to populate that table. All
568 packets from gardened users will be sent through this table. Example:
569
570 <PRE>
571 iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
572 iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
573 iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
574 iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
575 iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
576 iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
577 iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
578 iptables -t nat -A garden -p icmp -j ACCEPT
579 iptables -t nat -A garden -j DROP
580 </PRE>
581
582 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
583
584 A running l2tpns process can be controlled in a number of ways. The primary
585 method of control is by the Command-Line Interface (CLI).<P>
586
587 You can also remotely send commands to modules via the nsctl client
588 provided.<P>
589
590 Also, there are a number of signals that l2tpns understands and takes action
591 when it receives them.
592
593 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
594
595 You can access the command line interface by telnet'ing to port 23.
596 There is no IP address restriction, so it's a good idea to firewall
597 this port off from anyone who doesn't need access to it. See
598 <A HREF="#users">users</A> for information on restricting access based
599 on a username and password.<P>
600
601 The CLI gives you real-time control over almost everything in
602 the process. The interface is designed to look like a Cisco
603 device, and supports things like command history, line editing and
604 context sensitive help. This is provided by linking with the
605 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
606 library. Some general documentation of the interface is
607 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
608 here</A>.<P>
609
610 After you have connected to the telnet port (and perhaps logged in), you
611 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
612
613 Enter <EM>help</EM> to get a list of possible commands. A brief
614 overview of the more important commands follows:
615
616 <UL>
617 <LI><B>show session</B><BR>
618 Without specifying a session ID, this will list all tunnels currently
619 connected. If you specify a session ID, you will be given all
620 information on a single tunnel. Note that the full session list can
621 be around 185 columns wide, so you should probably use a wide terminal
622 to see the list properly.<P>
623 The columns listed in the overview are:
624 <TABLE>
625 <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
626 <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
627 <TR><TD><B>Username</B></TD><TD>The username given in the PPP
628 authentication. If this is *, then LCP authentication has not
629 completed.</TD></TR>
630 <TR><TD><B>IP</B></TD><TD>The IP address given to the session. If
631 this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
632 <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
633 session is being snooped. See <EM>snoop</EM>.</TD></TR>
634 <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
635 currently throttled. See <EM>throttle</EM>.</TD></TR>
636 <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
637 trapped in the walled garden. This field is present even if the
638 garden module is not loaded.</TD></TR>
639 <TR><TD><B>opened</B></TD><TD>The number of seconds since the
640 session started</TD></TR>
641 <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
642 <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
643 <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
644 detected on the session</TD></TR>
645 <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
646 connected to.</TD></TR>
647 <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
648 provided during the session setup. This field is generated by the
649 LAC.</TD></TR>
650 </TABLE>
651 <P>
652 </LI>
653
654 <LI><B>show users</B><BR>
655 With no arguments, display a list of currently connected users. If an
656 argument is given, the session details for the given username are
657 displayed.
658 </LI>
659
660 <LI><B>show tunnel</B><BR>
661 This will show all the open tunnels in a summary, or detail on a single
662 tunnel if you give a tunnel id.<P>
663 The columns listed in the overview are:
664 <TABLE>
665 <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
666 <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
667 provided by the LAC. This has no relation to DNS, it is just
668 a text field.</TD></TR>
669 <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
670 <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
671 Opening</TD></TR>
672 <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
673 tunnel</TD></TR>
674 </TABLE>
675 <P>
676 </LI>
677
678 <LI><B>show pool</B><BR>
679 Displays the current IP address pool allocation. This will only display
680 addresses that are in use, or are reserved for re-allocation to a
681 disconnected user.<P>
682 If an address is not currently in use, but has been used, then in the User
683 column the username will be shown in square brackets, followed by the time
684 since the address was used:
685 <PRE>
686 IP Address Used Session User
687 192.168.100.6 N [joe.user] 1548s
688 </PRE>
689 <P>
690 </LI>
691
692 <LI><B>show radius</B><BR>
693 Show a summary of the in-use RADIUS sessions. This list should not be very
694 long, as RADIUS sessions should be cleaned up as soon as they are used. The
695 columns listed are:
696 <TABLE>
697 <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request. This is
698 sent in the packet to the RADIUS server for identification.</TD></TR>
699 <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
700 AUTH, IPCP, START, STOP, NULL.</TD></TR>
701 <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
702 request is associated with</TD></TR>
703 <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
704 request, it will retry at this time. This is a unix timestamp.</TD></TR>
705 <TR><TD><B>Try</B></TD><TD>Retry count. The RADIUS request is
706 discarded after 3 retries.</TD></TR>
707 </TABLE>
708 <P>
709 </LI>
710
711 <LI><B>show running-config</B><BR>
712 This will list the current running configuration. This is in a format that
713 can either be pasted into the configuration file, or run directly at the
714 command line.
715 <P>
716 </LI>
717
718 <LI><B>show counters</B><BR>
719 Internally, counters are kept of key values, such as bytes and packets
720 transferred, as well as function call counters. This function displays all
721 these counters, and is probably only useful for debugging.<P>
722 You can reset these counters by running <EM>clear counters</EM>.
723 <P>
724 </LI>
725
726 <LI><B>show cluster</B><BR>
727 Show cluster status. Shows the cluster state for this server
728 (Master/Slave), information about known peers and (for slaves) the
729 master IP address, last packet seen and up-to-date status.<P>
730 See <A HREF="#Clustering">Clustering</A> for more information.
731 <P>
732 </LI>
733
734 <LI><B>write memory</B><BR>
735 This will write the current running configuration to the config file
736 <B>startup-config</B>, which will be run on a restart.
737 <P>
738 </LI>
739
740 <LI><B>snoop</B><BR>
741 You must specify a username, IP address and port. All packets for the
742 current session for that username will be forwarded to the given
743 host/port. Specify <EM>no snoop username</EM> to disable interception
744 for the session.<P>
745
746 If you want interception to be permanent, you will have to modify the RADIUS
747 response for the user. See <A HREF="#Interception">Interception</A>.
748 <P>
749 </LI>
750
751 <LI><B>throttle</B><BR>
752 You must specify a username, which will be throttled for the current
753 session. Specify <EM>no throttle username</EM> to disable throttling
754 for the current session.<P>
755
756 If you want throttling to be permanent, you will have to modify the
757 RADIUS response for the user. See <A HREF="#Throttling">Throttling</A>.
758 <P>
759 </LI>
760
761 <LI><B>drop session</B><BR>
762 This will cleanly disconnect a session. You must specify a session id, which
763 you can get from <EM>show session</EM>. This will send a disconnect message
764 to the remote end.
765 <P>
766 </LI>
767
768 <LI><B>drop tunnel</B><BR>
769 This will cleanly disconnect a tunnel, as well as all sessions on that
770 tunnel. It will send a disconnect message for each session individually, and
771 after 10 seconds it will send a tunnel disconnect message.
772 <P>
773 </LI>
774
775 <LI><B>uptime</B><BR>
776 This will show how long the l2tpns process has been running, and the current
777 bandwidth utilization:
778 <PRE>
779 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
780 Bandwidth: UDP-ETH:6/6 ETH-UDP:13/13 TOTAL:37.6 IN:3033 OUT:2569
781 </PRE>
782 The bandwidth line contains 4 sets of values.<BR>
783 UDP-ETH is the current bandwidth going from the LAC to the ethernet
784 (user uploads), in mbits/sec.<BR>
785 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
786 downloads).<BR>
787 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
788 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
789 <P>
790 These counters are updated every second.
791 <P>
792 </LI>
793
794 <LI><B>configure terminal</B><BR>
795 Enter configuration mode. Use <EM>exit</EM> or ^Z to exit this mode.
796 The following commands are valid in this mode:<P>
797 </LI>
798
799 <LI><B>load plugin</B><BR>
800 Load a plugin. You must specify the plugin name, and it will search in
801 /usr/lib/l2tpns for <EM>plugin</EM>.so. You can unload a loaded plugin with
802 <EM>remove plugin</EM>.
803 <P>
804 </LI>
805
806 <LI><B>set</B><BR>
807 Set a configuration variable. You must specify the variable name, and
808 the value. If the value contains any spaces, you should quote the
809 value with double (") or single (') quotes.<P>
810
811 You can set any <A HREF="#startup-config">startup-config</A> value in
812 this way, although some may require a restart to take effect.<P>
813 </LI>
814 </UL>
815
816 <H3 ID="nsctl">nsctl</H3>
817
818 nsctl allows messages to be passed to plugins.<P>
819
820 Arguments are <EM>command</EM> and optional <EM>args</EM>. See
821 <STRONG>nsctl</STRONG>(8) for more details.<P>
822
823 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
824 <EM>help</EM>. Any other commands are passed to plugins for processing.
825
826 <H3 ID="Signals">Signals</H3>
827
828 While the process is running, you can send it a few different signals, using
829 the kill command.
830 <PRE>
831 killall -HUP l2tpns
832 </PRE>
833
834 The signals understood are:
835 <DL>
836 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
837 <DT>SIGTERM, SIGINT</DT><DD>Stop process. Tunnels and sessions are not
838 terminated. This signal should be used to stop l2tpns on a
839 <A HREF="#Clustering">cluster node</A> where there are other machines to
840 continue handling traffic.</DD>
841 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
842 complete.</DD>
843 </DL>
844
845 <H2 ID="Throttling">Throttling</H2>
846
847 l2tpns contains support for slowing down user sessions to whatever speed you
848 desire. You must first enable the global setting <EM>throttle_speed</EM>
849 before this will be activated.<P>
850
851 If you wish a session to be throttled permanently, you should set the
852 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
853 will be handled by the <EM>autothrottle</EM> module.<P>
854
855 Otherwise, you can enable and disable throttling an active session using
856 the <EM>throttle</EM> CLI command.<P>
857
858 <H2 ID="Interception">Interception</H2>
859
860 You may have to deal with legal requirements to be able to intercept a
861 user's traffic at any time. l2tpns allows you to begin and end interception
862 on the fly, as well as at authentication time.<P>
863
864 When a user is being intercepted, a copy of every packet they send and
865 receive will be sent wrapped in a UDP packet to the IP address and port set
866 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
867 variables.<P>
868
869 The UDP packet contains just the raw IP frame, with no extra headers.<P>
870
871 To enable interception on a connected user, use the <EM>snoop username</EM>
872 and <EM>no snoop username</EM> CLI commands. These will enable interception
873 immediately.<P>
874
875 If you wish the user to be intercepted whenever they reconnect, you will
876 need to modify the RADIUS response to include the Vendor-Specific value
877 <B>Cisco-Avpair="intercept=yes"</B>. For this feature to be enabled,
878 you need to have the <EM>autosnoop</EM> module loaded.<P>
879
880 <H2 ID="Authentication">Authentication</H2>
881
882 Whenever a session connects, it is not fully set up until authentication is
883 completed. The remote end must send a PPP CHAP or PPP PAP authentication
884 request to l2tpns.<P>
885
886 This request is sent to the RADIUS server, which will hopefully respond with
887 Auth-Accept or Auth-Reject.<P>
888
889 If Auth-Accept is received, the session is set up and an IP address is
890 assigned. The RADIUS server can include a Framed-IP-Address field in the
891 reply, and that address will be assigned to the client. It can also include
892 specific DNS servers, and a Framed-Route if that is required.<P>
893
894 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
895 at which point they should disconnect. The exception to this is when the
896 walled garden module is loaded, in which case the user still receives the
897 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
898 should not receive any service.<P>
899
900 The RADIUS reply can also contain a Vendor-Specific attribute called
901 Cisco-Avpair. This field is a freeform text field that most Cisco
902 devices understand to contain configuration instructions for the session. In
903 the case of l2tpns it is expected to be of the form
904 <PRE>
905 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
906 </PRE>
907
908 Each key-value pair is separated and passed to any modules loaded. The
909 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
910 <EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
911 a user who is to be throttled and intercepted, the Cisco-Avpair value should
912 contain:
913 <PRE>
914 intercept=yes,throttle=yes
915 </PRE>
916
917 <H2 ID="Plugins">Plugins</H2>
918
919 So as to make l2tpns as flexible as possible (I know the core code is pretty
920 difficult to understand), it includes a plugin API, which you can use to
921 hook into certain events.<P>
922
923 There are a few example modules included - autosnoop, autothrottle and
924 garden.<P>
925
926 When an event happens that has a hook, l2tpns looks for a predefined
927 function name in every loaded module, and runs them in the order the modules
928 were loaded.<P>
929
930 The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
931 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
932 modules should be run for this event.<P>
933 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
934 no further processing should be done for this event. <EM>Use this with care.</EM>
935
936 Every event function called takes a specific structure named
937 param_<EM>event</EM>, which varies in content with each event. The
938 function name for each event will be <B>plugin_<EM>event</EM></B>,
939 so for the event <EM>timer</EM>, the function declaration should look like:
940 <PRE>
941 int plugin_timer(struct param_timer *data);
942 </PRE>
943
944 A list of the available events follows, with a list of all the fields in the
945 supplied structure:
946 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
947 <TABLE CELLSPACING=1 CELLPADDING=3>
948 <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
949 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
950 <TD>This is called after a RADIUS response has been
951 received, but before it has been processed by the
952 code. This will allow you to modify the response in
953 some way.
954 </TD>
955 <TD>
956 <DL>
957 <DT>t<DD>Tunnel
958 <DT>s<DD>Session
959 <DT>username
960 <DT>password
961 <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
962 <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
963 </DL>
964 </TD>
965 </TR>
966 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
967 <TD>This is called after a RADIUS response has been
968 received, and the basic checks have been performed. This
969 is what the garden module uses to force authentication
970 to be accepted.
971 </TD>
972 <TD>
973 <DL>
974 <DT>t<DD>Tunnel
975 <DT>s<DD>Session
976 <DT>username
977 <DT>auth_allowed<DD>This is already set to true or
978 false depending on whether authentication has been
979 allowed so far. You can set this to 1 or 0 to force
980 allow or disallow authentication
981 <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
982 </DL>
983 </TD>
984 </TR>
985 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
986 <TD>This is called whenever a session receives a
987 packet. <FONT COLOR=RED>Use this sparingly, as this will
988 seriously slow down the system.</FONT>
989 </TD>
990 <TD>
991 <DL>
992 <DT>t<DD>Tunnel
993 <DT>s<DD>Session
994 <DT>buf<DD>The raw packet data
995 <DT>len<DD>The length of buf
996 </DL>
997 </TD>
998 </TR>
999 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
1000 <TD>This is called whenever a session sends a
1001 packet. <FONT COLOR=RED>Use this sparingly, as this will
1002 seriously slow down the system.</FONT>
1003 </TD>
1004 <TD>
1005 <DL>
1006 <DT>t<DD>Tunnel
1007 <DT>s<DD>Session
1008 <DT>buf<DD>The raw packet data
1009 <DT>len<DD>The length of buf
1010 </DL>
1011 </TD>
1012 </TR>
1013 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
1014 <TD>This is run every second, no matter what is happening.
1015 This is called from a signal handler, so make sure anything
1016 you do is reentrant.
1017 </TD>
1018 <TD>
1019 <DL>
1020 <DT>time_now<DD>The current unix timestamp
1021 </DL>
1022 </TD>
1023 </TR>
1024 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
1025 <TD>This is called after a session is fully set up. The
1026 session is now ready to handle traffic.
1027 </TD>
1028 <TD>
1029 <DL>
1030 <DT>t<DD>Tunnel
1031 <DT>s<DD>Session
1032 </DL>
1033 </TD>
1034 </TR>
1035 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
1036 <TD>This is called when a session is about to be shut down.
1037 This may be called multiple times for the same session.
1038 </TD>
1039 <TD>
1040 <DL>
1041 <DT>t<DD>Tunnel
1042 <DT>s<DD>Session
1043 </DL>
1044 </TD>
1045 </TR>
1046 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
1047 <TD>This is called whenever a RADIUS response includes a
1048 Cisco-Avpair value. The value is split up into
1049 <EM>key=value</EM> pairs, and each is processed through all
1050 modules.
1051 </TD>
1052 <TD>
1053 <DL>
1054 <DT>t<DD>Tunnel
1055 <DT>s<DD>Session
1056 <DT>key
1057 <DT>value
1058 </DL>
1059 </TD>
1060 </TR>
1061 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
1062 <TD>This is called whenever a RADIUS CoA request is
1063 received to reset any options to default values before
1064 the new values are applied.
1065 </TD>
1066 <TD>
1067 <DL>
1068 <DT>t<DD>Tunnel
1069 <DT>s<DD>Session
1070 </DL>
1071 </TD>
1072 </TR>
1073 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
1074 <TD>This is called in whenever a nsctl packet is received.
1075 This should handle the packet and form a response if
1076 required.
1077 </TD>
1078 <TD>
1079 <DL>
1080 <DT>iam_master<DD>Cluster master status
1081 <DT>argc<DD>The number of arguments
1082 <DT>argv<DD>Arguments
1083 <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
1084 <DT>additional<DD>Extended response text
1085 </DL>
1086 </TD>
1087 </TR>
1088 </TABLE>
1089 </TD></TR></TABLE>
1090
1091 <H2 ID="WalledGarden">Walled Garden</H2>
1092
1093 Walled Garden is implemented so that you can provide perhaps limited service
1094 to sessions that incorrectly authenticate.<P>
1095
1096 Whenever a session provides incorrect authentication, and the
1097 RADIUS server responds with Auth-Reject, the walled garden module
1098 (if loaded) will force authentication to succeed, but set the flag
1099 <EM>garden</EM> in the session structure, and adds an iptables rule to
1100 the <B>garden_users</B> chain to force all packets for the session's IP
1101 address to traverse the <B>garden</B> chain.<P>
1102
1103 This doesn't <EM>just work</EM>. To set this all up, you will to
1104 setup the <B>garden</B> nat table with the
1105 <A HREF="#build-garden">build-garden</A> script with rules to limit
1106 user's traffic. For example, to force all traffic except DNS to be
1107 forwarded to 192.168.1.1, add these entries to your
1108 <EM>build-garden</EM>:
1109 <PRE>
1110 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
1111 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
1112 </PRE>
1113
1114 l2tpns will add entries to the garden_users chain as appropriate.<P>
1115
1116 You can check the amount of traffic being captured using the following
1117 command:
1118 <PRE>
1119 iptables -t nat -L garden -nvx
1120 </PRE>
1121
1122 <H2 ID="Filtering">Filtering</H2>
1123
1124 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1125 the RADIUS reply. <I>filter</I>.<B>in</B> specifies that the named
1126 access-list <I>filter</I> should be applied to traffic from the
1127 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1128 customer.
1129
1130 <H2 ID="Clustering">Clustering</H2>
1131
1132 An l2tpns cluster consists of of one* or more servers configured with
1133 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1134
1135 *A stand-alone server is simply a degraded cluster.<P>
1136
1137 Initially servers come up as cluster slaves, and periodically (every
1138 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1139 containing the start time of the process to the multicast
1140 <B>cluster_address</B>.<P>
1141
1142 A cluster master sends heartbeat rather than ping packets, which
1143 contain those session and tunnel changes since the last heartbeat.<P>
1144
1145 When a slave has not seen a heartbeat within
1146 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1147 examining the list of peers it has seen pings from and determines
1148 which of these and itself is the "best" candidate to be master.
1149 "Best" in this context means the server with the highest uptime (the
1150 highest IP address is used as a tie-breaker in the case of equal
1151 uptimes).<P>
1152
1153 After discovering a master, and determining that it is up-to-date (has
1154 seen an update for all in-use sessions and tunnels from heartbeat
1155 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1156 the <B>bind_address</B> and for all addresses/networks in
1157 <B>ip_pool</B>. Any packets recieved by the slave which would alter
1158 the session state, as well as packets for throttled or gardened
1159 sessions are forwarded to the master for handling. In addition, byte
1160 counters for session traffic are periodically forwarded.<P>
1161
1162 A master, when determining that it has at least one up-to-date slave
1163 will drop all routes (raising them again if all slaves disappear) and
1164 subsequently handle only packets forwarded to it by the slaves.<P>
1165
1166 <H2 ID="Routing">Routing</H2>
1167 If you are running a single instance, you may simply statically route
1168 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1169 arp).<P>
1170
1171 For a cluster, configure the members as BGP neighbours on your router
1172 and configure multi-path load-balancing. Cisco uses "maximum-paths
1173 ibgp" for IBGP. If this is not supported by your IOS revision, you
1174 can use "maximum-paths" (which works for EBGP) and set
1175 <B>as_number</B> to a private value such as 64512.<P>
1176
1177 <H2 ID="Performance">Performance</H2>
1178
1179 Performance is great.<P>
1180
1181 I'd like to include some pretty graphs here that show a linear performance
1182 increase, with no impact by number of connected sessions.<P>
1183
1184 That's really what it looks like.<P>
1185
1186 <BR>
1187 David Parrish<BR>
1188 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
1189 </BODY>
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