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