Docs/manual.html

   1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   2     "http://www.w3.org/TR/html4/loose.dtd">
   3
   4 <HTML>
   5 <HEAD>
   6 <TITLE>L2TPNS Manual</TITLE>
   7 <STYLE TYPE="text/css">
   8 H1 {
   9         text-align: center;
  10 }
  11
  12 H2 {
  13         border-top: 1px solid black;
  14         border-bottom: 1px solid black;
  15         background-color: lightblue;
  16         padding-left: 10px;
  17 }
  18
  19 H3 {
  20         text-decoration: underline;
  21 }
  22 </STYLE>
  23 </HEAD>
  24 <BODY>
  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 is half of a complete L2TP implementation.  It supports only the
  64 LNS side of the connection.<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>bind_address_remotelns</B> (ip address)<BR>
 383 Address of the interface to listen the remote LNS tunnels.
 384 If no address is given, all interfaces are listened (Any Address).
 385 </LI>
 386
 387 <LI><B>bind_portremotelns</B> (short)<BR>
 388 Port to bind for the Remote LNS (default: 65432).
 389 </LI>
 390
 391 <LI><B>auth_tunnel_change_addr_src</B> (boolean)<BR>
 392 This parameter authorize to change the source IP of the tunnels l2tp.
 393 This parameter can be used when the remotes BAS/LAC are l2tpns server
 394 configured in cluster mode, but that the interface to remote LNS are
 395 not clustered (the tunnel can be coming from different source IP)
 396 (default: no).
 397 </LI>
 398
 399 </UL>
 400
 401 <P>The REMOTES LNS configuration is entered by the command:
 402 <DL> <DD><B>setforward</B> <I>MASK</I> <I>IP</I> <I>PORT</I> <I>SECRET</I> </DL>
 403
 404 where <I>MASK</I> specifies the mask of users who have forwarded to
 405 remote LNS (ex: /myISP@company.com).</BR>
 406 where <I>IP</I> specifies the IP of the  remote LNS (ex: 66.66.66.55).</BR>
 407 where <I>PORT</I> specifies the L2TP Port of the remote LNS
 408 (Normally should be 1701) (ex: 1701).</BR>
 409 where <I>SECRET</I> specifies the secret password the remote LNS (ex: mysecret).</BR>
 410
 411 <P>BGP routing configuration is entered by the command:
 412 The routing configuration section is entered by the command
 413 <DL><DD><B>router bgp</B> <I>as</I></DL>
 414 where <I>as</I> specifies the local AS number.
 415
 416 <P>Subsequent lines prefixed with
 417 <DL><DD><B>neighbour</B> <I>peer</I></DL>
 418 define the attributes of BGP neighhbours.  Valid commands are:
 419 <DL>
 420   <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
 421   <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
 422 </DL>
 423
 424 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
 425 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
 426 <I>hold</I> are the timer values in seconds.
 427
 428 <P>Named access-lists are configured using one of the commands:
 429 <DL>
 430   <DD><B>ip access-list standard</B> <I>name</I>
 431   <DD><B>ip access-list extended</B> <I>name</I>
 432 </DL>
 433
 434 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
 435 define the body of the access-list.  Standard access-list syntax:
 436 <DL>
 437   <DD>{<B>permit</B>|<B>deny</B>}
 438     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 439     [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
 440 </DL>
 441
 442 Extended access-lists:
 443
 444 <DIV STYLE="margin-left: 4em; text-indent: -2em">
 445   <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
 446     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 447     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
 448   <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
 449     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 450         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 451     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 452         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 453         [<B>fragments</B>]
 454   <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
 455     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 456         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 457     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 458         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 459         [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
 460             {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
 461             ...|<B>fragments</B>]
 462 </DIV>
 463
 464 <H3 ID="users">users</H3>
 465
 466 Usernames and passwords for the command-line interface are stored in
 467 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 468 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 469 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 470 plain text by the prefix <B>{crypt}</B>.<P>
 471
 472 The username <B>enable</B> has a special meaning and is used to set
 473 the enable password.<P>
 474
 475 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 476 port 23 will be allowed access without a username / password.<P>
 477
 478 <H3 ID="ip-pool">ip_pool</H3>
 479
 480 This file is used to configure the IP address pool which user
 481 addresses are assigned from.  This file should contain either an IP
 482 address or a CIDR network per line.  e.g.:<P>
 483
 484 <PRE>
 485     192.168.1.1
 486     192.168.1.2
 487     192.168.1.3
 488     192.168.4.0/24
 489     172.16.0.0/16
 490     10.0.0.0/8
 491 </PRE>
 492
 493 Keep in mind that l2tpns can only handle 65535 connections per
 494 process, so don't put more than 65535 IP addresses in the
 495 configuration file.  They will be wasted.
 496
 497 <H3 ID="build-garden">build-garden</H3>
 498
 499 The garden plugin on startup creates a NAT table called "garden" then
 500 sources the <B>build-garden</B> script to populate that table.  All
 501 packets from gardened users will be sent through this table.  Example:
 502
 503 <PRE>
 504     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 505     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 506     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 507     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 508     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 509     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 510     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 511     iptables -t nat -A garden -p icmp -j ACCEPT
 512     iptables -t nat -A garden -j DROP
 513 </PRE>
 514
 515 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 516
 517 A running l2tpns process can be controlled in a number of ways.  The primary
 518 method of control is by the Command-Line Interface (CLI).<P>
 519
 520 You can also remotely send commands to modules via the nsctl client
 521 provided.<P>
 522
 523 Also, there are a number of signals that l2tpns understands and takes action
 524 when it receives them.
 525
 526 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 527
 528 You can access the command line interface by telnet'ing to port 23.
 529 There is no IP address restriction, so it's a good idea to firewall
 530 this port off from anyone who doesn't need access to it.  See
 531 <A HREF="#users">users</A> for information on restricting access based
 532 on a username and password.<P>
 533
 534 The CLI gives you real-time control over almost everything in
 535 the process.  The interface is designed to look like a Cisco
 536 device, and supports things like command history, line editing and
 537 context sensitive help.  This is provided by linking with the
 538 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 539 library.  Some general documentation of the interface is
 540 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 541 here</A>.<P>
 542
 543 After you have connected to the telnet port (and perhaps logged in), you
 544 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 545
 546 Enter <EM>help</EM> to get a list of possible commands.  A brief
 547 overview of the more important commands follows:
 548
 549 <UL>
 550 <LI><B>show session</B><BR>
 551 Without specifying a session ID, this will list all tunnels currently
 552 connected.  If you specify a session ID, you will be given all
 553 information on a single tunnel.  Note that the full session list can
 554 be around 185 columns wide, so you should probably use a wide terminal
 555 to see the list properly.<P>
 556 The columns listed in the overview are:
 557 <TABLE>
 558         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 559         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 560         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 561         authentication.  If this is *, then LCP authentication has not
 562         completed.</TD></TR>
 563         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 564         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 565         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 566         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 567         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 568         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 569         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 570         trapped in the walled garden.  This field is present even if the
 571         garden module is not loaded.</TD></TR>
 572         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 573         session started</TD></TR>
 574         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 575         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 576         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 577         detected on the session</TD></TR>
 578         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 579         connected to.</TD></TR>
 580         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 581         provided during the session setup.  This field is generated by the
 582         LAC.</TD></TR>
 583 </TABLE>
 584 <P>
 585 </LI>
 586
 587 <LI><B>show users</B><BR>
 588 With no arguments, display a list of currently connected users.  If an
 589 argument is given, the session details for the given username are
 590 displayed.
 591 </LI>
 592
 593 <LI><B>show tunnel</B><BR>
 594 This will show all the open tunnels in a summary, or detail on a single
 595 tunnel if you give a tunnel id.<P>
 596 The columns listed in the overview are:
 597 <TABLE>
 598         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 599         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 600         provided by the LAC.  This has no relation to DNS, it is just
 601         a text field.</TD></TR>
 602         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 603         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 604         Opening</TD></TR>
 605         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 606         tunnel</TD></TR>
 607 </TABLE>
 608 <P>
 609 </LI>
 610
 611 <LI><B>show pool</B><BR>
 612 Displays the current IP address pool allocation.  This will only display
 613 addresses that are in use, or are reserved for re-allocation to a
 614 disconnected user.<P>
 615 If an address is not currently in use, but has been used, then in the User
 616 column the username will be shown in square brackets, followed by the time
 617 since the address was used:
 618 <PRE>
 619 IP Address      Used  Session User
 620 192.168.100.6     N           [joe.user] 1548s
 621 </PRE>
 622 <P>
 623 </LI>
 624
 625 <LI><B>show radius</B><BR>
 626 Show a summary of the in-use RADIUS sessions.  This list should not be very
 627 long, as RADIUS sessions should be cleaned up as soon as they are used.  The
 628 columns listed are:
 629 <TABLE>
 630         <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request.  This is
 631         sent in the packet to the RADIUS server for identification.</TD></TR>
 632         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 633         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 634         <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
 635         request is associated with</TD></TR>
 636         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 637         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 638         <TR><TD><B>Try</B></TD><TD>Retry count.  The RADIUS request is
 639         discarded after 3 retries.</TD></TR>
 640 </TABLE>
 641 <P>
 642 </LI>
 643
 644 <LI><B>show running-config</B><BR>
 645 This will list the current running configuration.  This is in a format that
 646 can either be pasted into the configuration file, or run directly at the
 647 command line.
 648 <P>
 649 </LI>
 650
 651 <LI><B>show counters</B><BR>
 652 Internally, counters are kept of key values, such as bytes and packets
 653 transferred, as well as function call counters.  This function displays all
 654 these counters, and is probably only useful for debugging.<P>
 655 You can reset these counters by running <EM>clear counters</EM>.
 656 <P>
 657 </LI>
 658
 659 <LI><B>show cluster</B><BR>
 660 Show cluster status.  Shows the cluster state for this server
 661 (Master/Slave), information about known peers and (for slaves) the
 662 master IP address, last packet seen and up-to-date status.<P>
 663 See <A HREF="#Clustering">Clustering</A> for more information.
 664 <P>
 665 </LI>
 666
 667 <LI><B>write memory</B><BR>
 668 This will write the current running configuration to the config file
 669 <B>startup-config</B>, which will be run on a restart.
 670 <P>
 671 </LI>
 672
 673 <LI><B>snoop</B><BR>
 674 You must specify a username, IP address and port.  All packets for the
 675 current session for that username will be forwarded to the given
 676 host/port.  Specify <EM>no snoop username</EM> to disable interception
 677 for the session.<P>
 678
 679 If you want interception to be permanent, you will have to modify the RADIUS
 680 response for the user.  See <A HREF="#Interception">Interception</A>.
 681 <P>
 682 </LI>
 683
 684 <LI><B>throttle</B><BR>
 685 You must specify a username, which will be throttled for the current
 686 session.  Specify <EM>no throttle username</EM> to disable throttling
 687 for the current session.<P>
 688
 689 If you want throttling to be permanent, you will have to modify the
 690 RADIUS response for the user.  See <A HREF="#Throttling">Throttling</A>.
 691 <P>
 692 </LI>
 693
 694 <LI><B>drop session</B><BR>
 695 This will cleanly disconnect a session.  You must specify a session id, which
 696 you can get from <EM>show session</EM>.  This will send a disconnect message
 697 to the remote end.
 698 <P>
 699 </LI>
 700
 701 <LI><B>drop tunnel</B><BR>
 702 This will cleanly disconnect a tunnel, as well as all sessions on that
 703 tunnel.  It will send a disconnect message for each session individually, and
 704 after 10 seconds it will send a tunnel disconnect message.
 705 <P>
 706 </LI>
 707
 708 <LI><B>uptime</B><BR>
 709 This will show how long the l2tpns process has been running, and the current
 710 bandwidth utilization:
 711 <PRE>
 712 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 713 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 714 </PRE>
 715 The bandwidth line contains 4 sets of values.<BR>
 716 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 717 (user uploads), in mbits/sec.<BR>
 718 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 719 downloads).<BR>
 720 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 721 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 722 <P>
 723 These counters are updated every second.
 724 <P>
 725 </LI>
 726
 727 <LI><B>configure terminal</B><BR>
 728 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 729 The following commands are valid in this mode:<P>
 730 </LI>
 731
 732 <LI><B>load plugin</B><BR>
 733 Load a plugin.  You must specify the plugin name, and it will search in
 734 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 735 <EM>remove plugin</EM>.
 736 <P>
 737 </LI>
 738
 739 <LI><B>set</B><BR>
 740 Set a configuration variable.  You must specify the variable name, and
 741 the value.  If the value contains any spaces, you should quote the
 742 value with double (") or single (') quotes.<P>
 743
 744 You can set any <A HREF="#startup-config">startup-config</A> value in
 745 this way, although some may require a restart to take effect.<P>
 746 </LI>
 747 </UL>
 748
 749 <H3 ID="nsctl">nsctl</H3>
 750
 751 nsctl allows messages to be passed to plugins.<P>
 752
 753 Arguments are <EM>command</EM> and optional <EM>args</EM>.  See
 754 <STRONG>nsctl</STRONG>(8) for more details.<P>
 755
 756 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
 757 <EM>help</EM>.  Any other commands are passed to plugins for processing.
 758
 759 <H3 ID="Signals">Signals</H3>
 760
 761 While the process is running, you can send it a few different signals, using
 762 the kill command.
 763 <PRE>
 764 killall -HUP l2tpns
 765 </PRE>
 766
 767 The signals understood are:
 768 <DL>
 769 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
 770 <DT>SIGTERM, SIGINT</DT><DD>Stop process.  Tunnels and sessions are not
 771 terminated.  This signal should be used to stop l2tpns on a
 772 <A HREF="#Clustering">cluster node</A> where there are other machines to
 773 continue handling traffic.</DD>
 774 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
 775 complete.</DD>
 776 </DL>
 777
 778 <H2 ID="Throttling">Throttling</H2>
 779
 780 l2tpns contains support for slowing down user sessions to whatever speed you
 781 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 782 before this will be activated.<P>
 783
 784 If you wish a session to be throttled permanently, you should set the
 785 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
 786 will be handled by the <EM>autothrottle</EM> module.<P>
 787
 788 Otherwise, you can enable and disable throttling an active session using
 789 the <EM>throttle</EM> CLI command.<P>
 790
 791 <H2 ID="Interception">Interception</H2>
 792
 793 You may have to deal with legal requirements to be able to intercept a
 794 user's traffic at any time.  l2tpns allows you to begin and end interception
 795 on the fly, as well as at authentication time.<P>
 796
 797 When a user is being intercepted, a copy of every packet they send and
 798 receive will be sent wrapped in a UDP packet to the IP address and port set
 799 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 800 variables.<P>
 801
 802 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 803
 804 To enable interception on a connected user, use the <EM>snoop username</EM>
 805 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 806 immediately.<P>
 807
 808 If you wish the user to be intercepted whenever they reconnect, you will
 809 need to modify the RADIUS response to include the Vendor-Specific value
 810 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 811 you need to have the <EM>autosnoop</EM> module loaded.<P>
 812
 813 <H2 ID="Authentication">Authentication</H2>
 814
 815 Whenever a session connects, it is not fully set up until authentication is
 816 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 817 request to l2tpns.<P>
 818
 819 This request is sent to the RADIUS server, which will hopefully respond with
 820 Auth-Accept or Auth-Reject.<P>
 821
 822 If Auth-Accept is received, the session is set up and an IP address is
 823 assigned.  The RADIUS server can include a Framed-IP-Address field in the
 824 reply, and that address will be assigned to the client.  It can also include
 825 specific DNS servers, and a Framed-Route if that is required.<P>
 826
 827 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 828 at which point they should disconnect.  The exception to this is when the
 829 walled garden module is loaded, in which case the user still receives the
 830 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 831 should not receive any service.<P>
 832
 833 The RADIUS reply can also contain a Vendor-Specific attribute called
 834 Cisco-Avpair.  This field is a freeform text field that most Cisco
 835 devices understand to contain configuration instructions for the session.  In
 836 the case of l2tpns it is expected to be of the form
 837 <PRE>
 838 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 839 </PRE>
 840
 841 Each key-value pair is separated and passed to any modules loaded.  The
 842 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 843 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 844 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 845 contain:
 846 <PRE>
 847 intercept=yes,throttle=yes
 848 </PRE>
 849
 850 <H2 ID="Plugins">Plugins</H2>
 851
 852 So as to make l2tpns as flexible as possible (I know the core code is pretty
 853 difficult to understand), it includes a plugin API, which you can use to
 854 hook into certain events.<P>
 855
 856 There are a few example modules included - autosnoop, autothrottle and
 857 garden.<P>
 858
 859 When an event happens that has a hook, l2tpns looks for a predefined
 860 function name in every loaded module, and runs them in the order the modules
 861 were loaded.<P>
 862
 863 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 864 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 865 modules should be run for this event.<P>
 866 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 867 no further processing should be done for this event.  <EM>Use this with care.</EM>
 868
 869 Every event function called takes a specific structure named
 870 param_<EM>event</EM>, which varies in content with each event.  The
 871 function name for each event will be <B>plugin_<EM>event</EM></B>,
 872 so for the event <EM>timer</EM>, the function declaration should look like:
 873 <PRE>
 874 int plugin_timer(struct param_timer *data);
 875 </PRE>
 876
 877 A list of the available events follows, with a list of all the fields in the
 878 supplied structure:
 879 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 880 <TABLE CELLSPACING=1 CELLPADDING=3>
 881         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 882         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 883                 <TD>This is called after a RADIUS response has been
 884                 received, but before it has been processed by the
 885                 code.  This will allow you to modify the response in
 886                 some way.
 887                 </TD>
 888                 <TD>
 889                 <DL>
 890                         <DT>t<DD>Tunnel
 891                         <DT>s<DD>Session
 892                         <DT>username
 893                         <DT>password
 894                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 895                         <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
 896                 </DL>
 897                 </TD>
 898         </TR>
 899         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 900                 <TD>This is called after a RADIUS response has been
 901                 received, and the basic checks have been performed.  This
 902                 is what the garden module uses to force authentication
 903                 to be accepted.
 904                 </TD>
 905                 <TD>
 906                 <DL>
 907                         <DT>t<DD>Tunnel
 908                         <DT>s<DD>Session
 909                         <DT>username
 910                         <DT>auth_allowed<DD>This is already set to true or
 911                         false depending on whether authentication has been
 912                         allowed so far.  You can set this to 1 or 0 to force
 913                         allow or disallow authentication
 914                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 915                 </DL>
 916                 </TD>
 917         </TR>
 918         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 919                 <TD>This is called whenever a session receives a
 920                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 921                 seriously slow down the system.</FONT>
 922                 </TD>
 923                 <TD>
 924                 <DL>
 925                         <DT>t<DD>Tunnel
 926                         <DT>s<DD>Session
 927                         <DT>buf<DD>The raw packet data
 928                         <DT>len<DD>The length of buf
 929                 </DL>
 930                 </TD>
 931         </TR>
 932         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 933                 <TD>This is called whenever a session sends a
 934                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 935                 seriously slow down the system.</FONT>
 936                 </TD>
 937                 <TD>
 938                 <DL>
 939                         <DT>t<DD>Tunnel
 940                         <DT>s<DD>Session
 941                         <DT>buf<DD>The raw packet data
 942                         <DT>len<DD>The length of buf
 943                 </DL>
 944                 </TD>
 945         </TR>
 946         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
 947                 <TD>This is run every second, no matter what is happening.
 948                 This is called from a signal handler, so make sure anything
 949                 you do is reentrant.
 950                 </TD>
 951                 <TD>
 952                 <DL>
 953                         <DT>time_now<DD>The current unix timestamp
 954                 </DL>
 955                 </TD>
 956         </TR>
 957         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
 958                 <TD>This is called after a session is fully set up.  The
 959                 session is now ready to handle traffic.
 960                 </TD>
 961                 <TD>
 962                 <DL>
 963                         <DT>t<DD>Tunnel
 964                         <DT>s<DD>Session
 965                 </DL>
 966                 </TD>
 967         </TR>
 968         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
 969                 <TD>This is called when a session is about to be shut down.
 970                 This may be called multiple times for the same session.
 971                 </TD>
 972                 <TD>
 973                 <DL>
 974                         <DT>t<DD>Tunnel
 975                         <DT>s<DD>Session
 976                 </DL>
 977                 </TD>
 978         </TR>
 979         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
 980                 <TD>This is called whenever a RADIUS response includes a
 981                 Cisco-Avpair value.  The value is split up into
 982                 <EM>key=value</EM> pairs, and each is processed through all
 983                 modules.
 984                 </TD>
 985                 <TD>
 986                 <DL>
 987                         <DT>t<DD>Tunnel
 988                         <DT>s<DD>Session
 989                         <DT>key
 990                         <DT>value
 991                 </DL>
 992                 </TD>
 993         </TR>
 994         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
 995                 <TD>This is called whenever a RADIUS CoA request is
 996                 received to reset any options to default values before
 997                 the new values are applied.
 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>control</B></TD>
1007                 <TD>This is called in whenever a nsctl packet is received.
1008                 This should handle the packet and form a response if
1009                 required.
1010                 </TD>
1011                 <TD>
1012                 <DL>
1013                         <DT>iam_master<DD>Cluster master status
1014                         <DT>argc<DD>The number of arguments
1015                         <DT>argv<DD>Arguments
1016                         <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
1017                         <DT>additional<DD>Extended response text
1018                 </DL>
1019                 </TD>
1020         </TR>
1021 </TABLE>
1022 </TD></TR></TABLE>
1023
1024 <H2 ID="WalledGarden">Walled Garden</H2>
1025
1026 Walled Garden is implemented so that you can provide perhaps limited service
1027 to sessions that incorrectly authenticate.<P>
1028
1029 Whenever a session provides incorrect authentication, and the
1030 RADIUS server responds with Auth-Reject, the walled garden module
1031 (if loaded) will force authentication to succeed, but set the flag
1032 <EM>garden</EM> in the session structure, and adds an iptables rule to
1033 the <B>garden_users</B> chain to force all packets for the session's IP
1034 address to traverse the <B>garden</B> chain.<P>
1035
1036 This doesn't <EM>just work</EM>.  To set this all up, you will to
1037 setup the <B>garden</B> nat table with the
1038 <A HREF="#build-garden">build-garden</A> script with rules to limit
1039 user's traffic.  For example, to force all traffic except DNS to be
1040 forwarded to 192.168.1.1, add these entries to your
1041 <EM>build-garden</EM>:
1042 <PRE>
1043 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
1044 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
1045 </PRE>
1046
1047 l2tpns will add entries to the garden_users chain as appropriate.<P>
1048
1049 You can check the amount of traffic being captured using the following
1050 command:
1051 <PRE>
1052 iptables -t nat -L garden -nvx
1053 </PRE>
1054
1055 <H2 ID="Filtering">Filtering</H2>
1056
1057 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1058 the RADIUS reply.  <I>filter</I>.<B>in</B> specifies that the named
1059 access-list <I>filter</I> should be applied to traffic from the
1060 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1061 customer.
1062
1063 <H2 ID="Clustering">Clustering</H2>
1064
1065 An l2tpns cluster consists of of one* or more servers configured with
1066 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1067
1068 *A stand-alone server is simply a degraded cluster.<P>
1069
1070 Initially servers come up as cluster slaves, and periodically (every
1071 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1072 containing the start time of the process to the multicast
1073 <B>cluster_address</B>.<P>
1074
1075 A cluster master sends heartbeat rather than ping packets, which
1076 contain those session and tunnel changes since the last heartbeat.<P>
1077
1078 When a slave has not seen a heartbeat within
1079 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1080 examining the list of peers it has seen pings from and determines
1081 which of these and itself is the "best" candidate to be master.
1082 "Best" in this context means the server with the highest uptime (the
1083 highest IP address is used as a tie-breaker in the case of equal
1084 uptimes).<P>
1085
1086 After discovering a master, and determining that it is up-to-date (has
1087 seen an update for all in-use sessions and tunnels from heartbeat
1088 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1089 the <B>bind_address</B> and for all addresses/networks in
1090 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
1091 the session state, as well as packets for throttled or gardened
1092 sessions are forwarded to the master for handling.  In addition, byte
1093 counters for session traffic are periodically forwarded.<P>
1094
1095 A master, when determining that it has at least one up-to-date slave
1096 will drop all routes (raising them again if all slaves disappear) and
1097 subsequently handle only packets forwarded to it by the slaves.<P>
1098
1099 <H2 ID="Routing">Routing</H2>
1100 If you are running a single instance, you may simply statically route
1101 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1102 arp).<P>
1103
1104 For a cluster, configure the members as BGP neighbours on your router
1105 and configure multi-path load-balancing.  Cisco uses "maximum-paths
1106 ibgp" for IBGP.  If this is not supported by your IOS revision, you
1107 can use "maximum-paths" (which works for EBGP) and set
1108 <B>as_number</B> to a private value such as 64512.<P>
1109
1110 <H2 ID="Performance">Performance</H2>
1111
1112 Performance is great.<P>
1113
1114 I'd like to include some pretty graphs here that show a linear performance
1115 increase, with no impact by number of connected sessions.<P>
1116
1117 That's really what it looks like.<P>
1118
1119 <BR>
1120 David Parrish<BR>
1121 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
1122 </BODY>
1123 </HTML>