1.\" $NetBSD: mrouted.8,v 1.17 2009/03/15 10:16:28 joerg Exp $ 2.\" $OpenBSD: mrouted.8,v 1.11 2003/03/03 15:14:28 deraadt Exp $ 3.\" The mrouted program is covered by the license in the accompanying file 4.\" named "LICENSE". Use of the mrouted program represents acceptance of 5.\" the terms and conditions listed in that file. 6.\" 7.\" The mrouted program is COPYRIGHT 1989 by The Board of Trustees of 8.\" Leland Stanford Junior University. 9.Dd May 8, 1995 10.Dt MROUTED 8 11.Os 12.Sh NAME 13.Nm mrouted 14.Nd IP multicast routing daemon 15.Sh SYNOPSIS 16.Nm mrouted 17.Op Fl c Ar config_file 18.Op Fl d Ar debug_level 19.Op Fl p 20.Sh DESCRIPTION 21.Nm 22is an implementation of the Distance-Vector Multicast Routing 23Protocol (DVMRP), an earlier version of which is specified in RFC 1075. 24It maintains topological knowledge via a distance-vector routing protocol 25(like RIP, described in RFC 1058), upon which it implements a multicast 26datagram forwarding algorithm called Reverse Path Multicasting. 27.Pp 28.Nm 29forwards a multicast datagram along a shortest (reverse) path tree 30rooted at the subnet on which the datagram originates. 31The multicast 32delivery tree may be thought of as a broadcast delivery tree that has 33been pruned back so that it does not extend beyond those subnetworks 34that have members of the destination group. 35Hence, datagrams are not forwarded along those branches which have no 36listeners of the multicast group. 37The IP time-to-live of a multicast datagram can be 38used to limit the range of multicast datagrams. 39.Pp 40In order to support multicasting among subnets that are separated by (unicast) 41routers that do not support IP multicasting, 42.Nm 43includes support for 44"tunnels", which are virtual point-to-point links between pairs of 45.Nm 46daemons located anywhere in an internet. 47IP multicast packets are encapsulated 48for transmission through tunnels, so that they look like normal unicast 49datagrams to intervening routers and subnets. 50The encapsulation is added on 51entry to a tunnel, and stripped off on exit from a tunnel. 52By default, the packets are encapsulated using the IP-in-IP protocol 53(IP protocol number 4). 54Older versions of 55.Nm 56tunnel using IP source routing, which puts a heavy load on some 57types of routers. 58This version does not support IP source route tunneling. 59.Pp 60The tunneling mechanism allows 61.Nm 62to establish a virtual internet, for 63the purpose of multicasting only, which is independent of the physical 64internet, and which may span multiple Autonomous Systems. 65This capability 66is intended for experimental support of internet multicasting only, pending 67widespread support for multicast routing by the regular (unicast) routers. 68.Nm 69suffers from the well-known scaling problems of any distance-vector 70routing protocol, and does not (yet) support hierarchical multicast routing. 71.Pp 72.Nm 73handles multicast routing only; there may or may not be unicast routing 74software running on the same machine as 75.Nm mrouted . 76With the use of tunnels, it is not necessary for 77.Nm 78to have access to more than one physical subnet 79in order to perform multicast forwarding. 80.Sh INVOCATION 81If no 82.Fl d 83option is given, or if the debug level is specified as 0, 84.Nm 85detaches from the invoking terminal. 86Otherwise, it remains attached to the 87invoking terminal and responsive to signals from that terminal. 88If 89.Fl d 90is given with no argument, the debug level defaults to 2. 91Regardless of the debug level, 92.Nm 93always writes warning and error messages to the system 94log daemon. 95Non-zero debug levels have the following effects: 96.Bl -hang -compact -offset indent 97.It 1 98all syslog'ed messages are also printed to stderr. 99.It 2 100all level 1 messages plus notifications of "significant" 101events are printed to stderr. 102.It 3 103all level 2 messages plus notifications of all packet 104arrivals and departures are printed to stderr. 105.El 106.Pp 107Upon startup, mrouted writes its pid to the file 108.Pa /var/run/mrouted.pid . 109.Sh CONFIGURATION 110.Nm 111automatically configures itself to forward on all multicast-capable 112interfaces, i.e., interfaces that have the IFF_MULTICAST flag set (excluding 113the loopback "interface"), and it finds other 114.Nm 115directly reachable via those interfaces. 116To override the default configuration, or to add tunnel links to other 117.Nm 118configuration commands may be placed in 119.Pa /etc/mrouted.conf 120(or an alternative file, specified by the 121.Fl c 122option). 123There are four types of configuration commands: 124.Bl -item -offset indent 125.It 126.Tn phyint \*[Lt]local-addr\*[Gt] [disable] [metric \*[Lt]m\*[Gt]] 127.Bl -tag -width flag -compact -offset indent 128.It [threshold \*[Lt]t\*[Gt]] [rate_limit \*[Lt]b\*[Gt]] 129.It [boundary (\*[Lt]boundary-name\*[Gt]|\*[Lt]scoped-addr\*[Gt]/\*[Lt]mask-len\*[Gt])] 130.It [altnet \*[Lt]network\*[Gt]/\*[Lt]mask-len\*[Gt]] 131.El 132.It 133.Bl -tag -width flag -compact -offset indent 134.It Tn tunnel \*[Lt]local-addr\*[Gt] \*[Lt]remote-addr\*[Gt] [metric \*[Lt]m\*[Gt]] 135.It [threshold \*[Lt]t\*[Gt]] [rate_limit \*[Lt]b\*[Gt]] 136.It [boundary (\*[Lt]boundary-name\*[Gt]|\*[Lt]scoped-addr\*[Gt]/\*[Lt]mask-len\*[Gt])] 137.El 138.It 139.Tn cache_lifetime \*[Lt]ct\*[Gt] 140.It 141.Tn pruning \*[Lt]off/on\*[Gt] 142.It 143.Tn name \*[Lt]boundary-name\*[Gt] \*[Lt]scoped-addr\*[Gt]/\*[Lt]mask-len\*[Gt] 144.El 145.Pp 146The file format is free-form; whitespace (including newlines) is not 147significant. 148The 149.Ar boundary 150and 151.Ar altnet 152options may be specified as many times as necessary. 153.Pp 154The phyint command can be used to disable multicast routing on the physical 155interface identified by local IP address 156.Ar \*[Lt]local-addr\*[Gt] , 157or to associate a non-default metric or threshold with the specified 158physical interface. 159The local IP address 160.Ar \*[Lt]local-addr\*[Gt] 161may be replaced by the interface name (e.g., le0). 162If a phyint is attached to multiple IP subnets, describe each additional subnet 163with the altnet keyword. 164Phyint commands must precede tunnel commands. 165.Pp 166The tunnel command can be used to establish a tunnel link between local 167IP address 168.Ar \*[Lt]local-addr\*[Gt] 169and remote IP address 170.Ar \*[Lt]remote-addr\*[Gt] , 171and to associate a non-default metric or threshold with that tunnel. 172The local IP address 173.Ar \*[Lt]local-addr\*[Gt] 174may be replaced by the interface name (e.g., le0). 175The remote IP address 176.Ar \*[Lt]remote-addr\*[Gt] 177may be replaced by a host name, if and only if the host name has a single 178IP address associated with it. 179The tunnel must be set up in the mrouted.conf files of both routers before 180it can be used. 181.\"For backwards compatibility with older 182.\".IR mrouted s, 183.\"the srcrt keyword specifies 184.\"encapsulation using IP source routing. 185.Pp 186The cache_lifetime is a value that determines the amount of time that a 187cached multicast route stays in kernel before timing out. 188The value of this entry should lie between 300 (5 min) and 86400 (1 day). 189It defaults to 300. 190.Pp 191The 192.Ar pruning 193option is provided for 194.Nm 195to act as a non-pruning router. 196It is also possible to start 197.Nm 198in a non-pruning mode using the 199.Fl p 200option on the command line. 201It is expected that a router would be configured 202in this manner for test purposes only. 203The default mode is pruning enabled. 204.Pp 205You may assign names to boundaries to make configuration easier with 206the name keyword. 207The boundary option on phyint or tunnel commands 208can accept either a name or a boundary. 209.Pp 210The metric is the "cost" associated with sending a datagram on the given 211interface or tunnel; it may be used to influence the choice of routes. 212The metric defaults to 1. 213Metrics should be kept as small as possible, because 214.Nm 215cannot route along paths with a sum of metrics greater than 31. 216.Pp 217The threshold is the minimum IP time-to-live required for a multicast datagram 218to be forwarded to the given interface or tunnel. 219It is used to control the scope of multicast datagrams. 220(The TTL of forwarded packets is only compared 221to the threshold, it is not decremented by the threshold. 222Every multicast router decrements the TTL by 1.) 223The default threshold is 1. 224.Pp 225In general, all 226.Nm 227connected to a particular subnet or tunnel should 228use the same metric and threshold for that subnet or tunnel. 229.Pp 230The rate_limit option allows the network administrator to specify a 231certain bandwidth in Kbits/second which would be allocated to multicast 232traffic. 233It defaults to 500Kbps on tunnels, and 0 (unlimited) on physical 234interfaces. 235.Pp 236The boundary option allows an interface 237to be configured as an administrative boundary for the specified 238scoped address. 239Packets belonging to this address will not 240be forwarded on a scoped interface. 241The boundary option accepts either 242a name or a boundary spec. 243.Pp 244.Nm 245will not initiate execution if it has fewer than two enabled vifs, 246where a vif (virtual interface) is either a physical multicast-capable 247interface or a tunnel. 248It will log a warning if all of its vifs are tunnels; such an 249.Nm 250configuration would be better replaced by more 251direct tunnels (i.e., eliminate the middle man). 252.Sh EXAMPLE CONFIGURATION 253This is an example configuration for a mythical multicast router at a big 254school. 255.Bd -unfilled -compact -offset left 256# 257# mrouted.conf example 258# 259# Name our boundaries to make it easier. 260name LOCAL 239.255.0.0/16 261name EE 239.254.0.0/16 262# 263# le1 is our gateway to compsci, don't forward our 264# local groups to them. 265phyint le1 boundary EE 266# 267# le2 is our interface on the classroom net, it has four 268# different length subnets on it. 269# Note that you can use either an ip address or an 270# interface name 271phyint 172.16.12.38 boundary EE altnet 172.16.15.0/26 272 altnet 172.16.15.128/26 altnet 172.16.48.0/24 273# 274# atm0 is our ATM interface, which doesn't properly 275# support multicasting. 276phyint atm0 disable 277# 278# This is an internal tunnel to another EE subnet. 279# Remove the default tunnel rate limit, since this 280# tunnel is over ethernets. 281tunnel 192.168.5.4 192.168.55.101 metric 1 threshold 1 282 rate_limit 0 283# 284# This is our tunnel to the outside world. 285# Careful with those boundaries, Eugene. 286tunnel 192.168.5.4 10.11.12.13 metric 1 threshold 32 287 boundary LOCAL boundary EE 288.Ed 289.Sh SIGNALS 290.Nm 291responds to the following signals: 292.Bl -tag -width TERM -compact 293.It HUP 294restarts 295.Nm mrouted . 296The configuration file is reread every time this signal is evoked. 297.It INT 298terminates execution gracefully (i.e., by sending 299good-bye messages to all neighboring routers). 300.It TERM 301same as INT 302.It USR1 303dumps the internal routing tables to 304.Pa /var/tmp/mrouted.dump . 305.It USR2 306dumps the internal cache tables to 307.Pa /var/tmp/mrouted.cache . 308.It QUIT 309dumps the internal routing tables to stderr (only if 310.Nm 311was invoked with a non-zero debug level). 312.El 313.Pp 314For convenience in sending signals, 315.Nm 316writes its pid to 317.Pa /var/run/mrouted.pid 318upon startup. 319.Sh FILES 320.Bl -tag -width /var/tmp/mrouted.cache -compact 321.It Pa /etc/mrouted.conf 322.It Pa /var/run/mrouted.pid 323.It Pa /var/tmp/mrouted.dump 324.It Pa /var/tmp/mrouted.cache 325.El 326.Sh EXAMPLES 327The routing tables look like this: 328.Pp 329.Bd -literal -compact -offset left 330Virtual Interface Table 331 Vif Local-Address Metric Thresh Flags 332 0 36.2.0.8 subnet: 36.2 1 1 querier 333 groups: 224.0.2.1 334 224.0.0.4 335 pkts in: 3456 336 pkts out: 2322323 337 338 1 36.11.0.1 subnet: 36.11 1 1 querier 339 groups: 224.0.2.1 340 224.0.1.0 341 224.0.0.4 342 pkts in: 345 343 pkts out: 3456 344 345 2 36.2.0.8 tunnel: 36.8.0.77 3 1 346 peers: 36.8.0.77 (2.2) 347 boundaries: 239.0.1 348 : 239.1.2 349 pkts in: 34545433 350 pkts out: 234342 351 352 3 36.2.0.8 tunnel: 36.6.8.23 3 16 353 354Multicast Routing Table (1136 entries) 355 Origin-Subnet From-Gateway Metric Tmr In-Vif Out-Vifs 356 36.2 1 45 0 1* 2 3* 357 36.8 36.8.0.77 4 15 2 0* 1* 3* 358 36.11 1 20 1 0* 2 3* 359 . 360 . 361 . 362.Ed 363.Pp 364In this example, there are four vifs connecting to two subnets and two 365tunnels. 366The vif 3 tunnel is not in use (no peer address). 367The vif 0 and 368vif 1 subnets have some groups present; tunnels never have any groups. 369This instance of 370.Nm 371is the one responsible for sending periodic group 372membership queries on the vif 0 and vif 1 subnets, as indicated by the 373"querier" flags. 374The list of boundaries indicate the scoped addresses on that interface. 375A count of the number of incoming and outgoing packets is also 376shown at each interface. 377.Pp 378Associated with each subnet from which a multicast datagram can originate 379is the address of the previous hop router (unless the subnet is directly- 380connected), the metric of the path back to the origin, the amount of time 381since we last received an update for this subnet, the incoming vif for 382multicasts from that origin, and a list of outgoing vifs. 383"*" means that 384the outgoing vif is connected to a leaf of the broadcast tree rooted at the 385origin, and a multicast datagram from that origin will be forwarded on that 386outgoing vif only if there are members of the destination group on that leaf. 387.Pp 388.Nm 389also maintains a copy of the kernel forwarding cache table. 390Entries are created and deleted by 391.Nm mrouted . 392.Pp 393The cache tables look like this: 394.Pp 395.Bd -unfilled -compact -offset left 396Multicast Routing Cache Table (147 entries) 397 Origin Mcast-group CTmr Age Ptmr IVif Forwvifs 398 13.2.116/22 224.2.127.255 3m 2m - 0 1 399\*[Gt]13.2.116.19 400\*[Gt]13.2.116.196 401 138.96.48/21 224.2.127.255 5m 2m - 0 1 402\*[Gt]138.96.48.108 403 128.9.160/20 224.2.127.255 3m 2m - 0 1 404\*[Gt]128.9.160.45 405 198.106.194/24 224.2.135.190 9m 28s 9m 0P 406\*[Gt]198.106.194.22 407.Ed 408.Pp 409Each entry is characterized by the origin subnet number and mask and the 410destination multicast group. 411The 'CTmr' field indicates the lifetime of the entry. 412The entry is deleted from the cache table 413when the timer decrements to zero. 414The 'Age' field is the time since 415this cache entry was originally created. 416Since cache entries get refreshed 417if traffic is flowing, routing entries can grow very old. 418The 'Ptmr' field is simply a dash if no prune was sent upstream, or the 419amount of time until the upstream prune will time out. 420The 'Ivif' field indicates the 421incoming vif for multicast packets from that origin. 422Each router also 423maintains a record of the number of prunes received from neighboring 424routers for a particular source and group. 425If there are no members of 426a multicast group on any downward link of the multicast tree for a 427subnet, a prune message is sent to the upstream router. 428They are indicated by a "P" after the vif number. 429The Forwvifs field shows the 430interfaces along which datagrams belonging to the source-group are 431forwarded. 432A "p" indicates that no datagrams are being forwarded along 433that interface. 434An unlisted interface is a leaf subnet with are no 435members of the particular group on that subnet. 436A "b" on an interface 437indicates that it is a boundary interface, i.e., traffic will not be 438forwarded on the scoped address on that interface. 439An additional line with a "\*[Gt]" as the first character is printed for 440each source on the subnet. 441Note that there can be many sources in one subnet. 442.Sh SEE ALSO 443.Xr map-mbone 8 , 444.Xr mrinfo 8 , 445.Xr mtrace 8 446.Pp 447DVMRP is described, along with other multicast routing algorithms, in the 448paper "Multicast Routing in Internetworks and Extended LANs" by S. Deering, 449in the Proceedings of the ACM SIGCOMM '88 Conference. 450.Sh AUTHORS 451Steve Deering, Ajit Thyagarajan, Bill Fenner 452