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MROUTED(8)              FreeBSD System Manager's Manual             MROUTED(8)

       mrouted - IP multicast routing daemon

       /usr/sbin/mrouted [ -c config_file ] [ -d [ debug_level ]]

       Mrouted is an implementation of the Distance-Vector Multicast Routing
       Protocol (DVMRP), an earlier version of which is specified in RFC-1075.
       It maintains topological knowledge via a distance-vector routing
       protocol (like RIP, described in RFC-1058), upon which it implements a
       multicast datagram forwarding algorithm called Reverse Path

       Mrouted forwards a multicast datagram along a shortest (reverse) path
       tree rooted at the subnet on which the datagram originates. The
       multicast delivery tree may be thought of as a broadcast delivery tree
       that has been pruned back so that it does not extend beyond those
       subnetworks that have members of the destination group. Hence,
       datagrams are not forwarded along those branches which have no
       listeners of the multicast group. The IP time-to-live of a multicast
       datagram can be used to limit the range of multicast datagrams.

       In order to support multicasting among subnets that are separated by
       (unicast) routers that do not support IP multicasting, mrouted includes
       support for "tunnels", which are virtual point-to-point links between
       pairs of multicast routers located anywhere in an internet.  IP
       multicast packets are encapsulated for transmission through tunnels, so
       that they look like normal unicast datagrams to intervening routers and
       subnets.  The encapsulation is added on entry to a tunnel, and stripped
       off on exit from a tunnel.  The packets are encapsulated using the IP-
       in-IP protocol (IP protocol number 4).  Older versions of mrouted
       tunneled using IP source routing, which puts a heavy load on some types
       of routers.  This version does not support IP source route tunnelling.

       The tunnelling mechanism allows mrouted to establish a virtual
       internet, for the purpose of multicasting only, which is independent of
       the physical internet, and which may span multiple Autonomous Systems.
       This capability is intended for experimental support of internet
       multicasting only, pending widespread support for multicast routing by
       the regular (unicast) routers.  Mrouted suffers from the well-known
       scaling problems of any distance-vector routing protocol, and does not
       (yet) support hierarchical multicast routing.

       Mrouted handles multicast routing only; there may or may not be unicast
       routing software running on the same machine as mrouted.  With the use
       of tunnels, it is not necessary for mrouted to have access to more than
       one physical subnet in order to perform multicast forwarding.

       -c config_file
                 Specifies an alternate configuration file to read (normally

       -d debug_level
                 Turn on debugging; debug_level is a comma-seperated list of
                 subsections to debug.

       If no "-d" option is given, mrouted detaches from the invoking
       terminal.  Otherwise, it remains attached to the invoking terminal and
       responsive to signals from that terminal.  Regardless of the debug
       level, mrouted always writes warning and error messages to the system
       log demon.  The debug-level argument is a comma-seperated list of any
       of the following:

       packet       Display the type, source and destination of all packets
                    sent or received.

       pruning      Display more information about prunes sent or received.

       routing      Display more information about routing update packets sent
                    or received.

       route_detail Display routing updates in excruciating detail.  This is
                    generally way too much information.

       neighbors    Display information about neighbor discovery.

       cache        Display insertions, deletions and refreshes of entries in
                    the kernel forwarding cache.

       timeout      Debug timeouts and periodic processes.

       interface    Display information about interfaces and their

       membership   Display information about group memberships on physical

       traceroute   Display information about multicast traceroute requests
                    passing through this router.

       igmp         Display IGMP operation including group membership and
                    querier election.

       icmp         Monitor ICMP handling.

       rsrr         Monitor RSRR operation.

       Upon startup, mrouted writes its pid to the file /var/run/ .

       Mrouted automatically configures itself to forward on all multicast-
       capable interfaces, i.e., interfaces that have the IFF_MULTICAST flag
       set (excluding the loopback "interface"), and it finds other DVMRP
       routers directly reachable via those interfaces.  To override the
       default configuration, or to add tunnel links to other multicast
       routers, configuration commands may be placed in /etc/mrouted.conf (or
       an alternative file, specified by the "-c" option).

       The file format is free-form; whitespace (including newlines) is not
       significant.  The file begins with commands that apply to mrouted's
       overall operation or set defaults.

       cache_lifetime secs
                      Specifies, in seconds, the lifetime of a multicast
                      forwarding cache entry in the kernel.  Multicast
                      forwarding cache entries in the kernel are checked every
                      secs seconds, and are refreshed if the source is still
                      active or deleted if not.  Care should be taken when
                      setting this value, as a low value can keep the kernel
                      cache small at the cost of "thrashing" the cache for
                      periodic senders, but high values can cause the kernel
                      cache to grow unacceptably large.  The default is 300
                      seconds (5 minutes).

       prune_lifetime secs
                      Sepcifies, in seconds, the average lifetime of prunes
                      that are sent towards parents.  The actual lifetimes
                      will be randomized in the range [.5secs,1.5secs].  The
                      default is 7200 (2 hours).  Smaller values cause less
                      state to be kept both at this router and the parent, at
                      the cost of more frequent broadcasts.  However, some
                      routers (e.g. mrouted <3.3 and all currently known
                      versions of cisco's IOS) do not use the DVMRP generation
                      ID to determine that a neighbor has rebooted.  Prunes
                      sent towards these neighbors should be kept short, in
                      order to shorten the time to recover from a reboot.  For
                      use in this situation, the prune_lifetime keyword may be
                      specified on an interface as described below.

       noflood        Mrouted uses a DVMRP optimization to prevent having to
                      keep individual routing tables for each neighbor; part
                      of this optimization is that mrouted assumes that it is
                      the forwarder for each of its attached subnets on
                      startup.  This can cause duplicates for a short period
                      (approximately one full route report interval), since
                      both the router that just started up and the proper
                      forwarder will be forwarding traffic.  This behavior can
                      be turned off with the noflood keyword; mrouted will not
                      assume that it is the forwarder on startup.  Turning on
                      noflood can cause black holes on restart, which will
                      generally last approximately one full route report
                      interval.  The noflood keyword can also be specified on
                      individual interfaces.

       rexmit_prunes [on|off]
                      Mrouted's default is to retransmit prunes on all point-
                      to-point interfaces (including tunnels) but no multi-
                      access interfaces.  This option may be used to make the
                      default on (or off) for all interfaces.  The
                      rexmit_prunes keyword can also be specified on
                      individual interfaces.

       name boundary-name scoped-addr/mask-len
                      Associates boundary-name with the boundary described by
                      scoped-addr/mask-len, to help make interface
                      configurations more readable and reduce repetition in
                      the configuration file.

       The second section of the configuration file, which may optionally be
       empty, describes options that apply to physical interfaces.

       phyint local-addr|ifname
                      The phyint command does nothing by itself; it is simply
                      a place holder which interface-specific commands may
                      follow.  An interface address or name may be specified.

       disable        Disables multicast forwarding on this interface.  By
                      default, mrouted discovers all locally attached
                      multicast capable interfaces and forwards on all of

       netmask netmask
                      If the kernel's netmask does not accurately reflect the
                      subnet (e.g. you're using proxy-ARP in lieu of IP
                      subnetting), use the netmask command to describe the
                      real netmask.

       altnet network/mask-len
                      If a phyint is attached to multiple IP subnets, describe
                      each additional subnet with the altnet keyword.  This
                      command may be specified multiple times to describe
                      multiple subnets.

       igmpv1         If there are any IGMPv1 routers on the phyint, use the
                      igmpv1 keyword to force mrouted into IGMPv1 mode.  All
                      routers on the phyint must use the same version of IGMP.

       force_leaf     Force mrouted to ignore other routers on this interface.
                      mrouted will never send or accept neighbor probes or
                      route reports on this interface.

       In addition, the common vif commands described later may all be used on
       a phyint.

       The third section of the configuration file, also optional, describes
       the configuration of any DVMRP tunnels this router might have.

       tunnel local-addr|ifname remote-addr|remote-hostname
                      This command establishes a DVMRP tunnel between this
                      host (on the interface described by local-addr or
                      ifname) and a remote host (identified by remote-addr or
                      remote-hostname).  A remote hostname may only be used if
                      it maps to a single IP address.  A tunnel must be
                      configured on both routers before it can be used.

                      Be careful that the unicast route to the remote address
                      goes out the interface specified by the
                      local-addr|ifname argument.  Some UNIX kernels rewrite
                      the source address of mrouted's packets on their way out
                      to contain the address of the transmission interface.
                      This is best assured via a static host route.

       The common vif commands described below may all be used on tunnels or

       metric m       The metric is the "cost" associated with receiving a
                      datagram on the given interface or tunnel; it may be
                      used to influence the choice of routes.  The metric
                      defaults to 1.  Metrics should be kept as small as
                      possible, because DVMRP cannot route along paths with a
                      sum of metrics greater than 31.

       advert_metric m
                      The advert_metric is the "cost" associated with sending
                      a datagram on the given interface or tunnel; it may be
                      used to influence the choice of routes.  The
                      advert_metric defaults to 0.  Note that the effective
                      metric of a link is one end's metric plus the other
                      end's advert_metric.

       threshold t    The threshold is the minimum IP time-to-live required
                      for a multicast datagram to be forwarded to the given
                      interface or tunnel.  It is used to control the scope of
                      multicast datagrams.  (The TTL of forwarded packets is
                      only compared to the threshold, it is not decremented by
                      the threshold.  Every multicast router decrements the
                      TTL by exactly 1.)  The default threshold is 1.

       In general, all multicast routers connected to a particular subnet or
       tunnel should use the same metric and threshold for that subnet or

       rate_limit r   The rate_limit option allows the network administrator
                      to specify a certain bandwidth in Kbits/second which
                      would be allocated to multicast traffic.  It defaults 0

       boundary boundary-name|scoped-addr/mask-len
                      The boundary option allows an interface to be configured
                      as an administrative boundary for the specified scoped
                      address. Packets belonging to this address will not be
                      forwarded on a scoped interface.  The boundary option
                      accepts either a name or a boundary spec.  This command
                      may be specified several times on an interface in order
                      to describe multiple boundaries.

       passive        No packets will be sent on this link or tunnel until we
                      hear from the other end.  This is useful for the
                      "server" end of a tunnel that goes over a dial-on-demand
                      link; configure the "server" end as passive and it will
                      not send its periodic probes until it hears one from the
                      other side, so will not keep the link up.  If this
                      option is specified on both ends of a tunnel, the tunnel
                      will never come up.

       noflood        As described above, but only applicable to this

       prune_lifetime secs
                      As described above, but only applicable to this

       rexmit_prunes [on|off]
                      As described above, but only applicable to this
                      interface/tunnel.  Recall that prune retransmission
                      defaults to on on point-to-point links and tunnels, and
                      off on multi-access links.

                      By default, mrouted refuses to peer with DVMRP neighbors
                      that do not claim to support pruning.  This option
                      allows such peerings on this interface.

       notransit      A specialized case of route filtering; no route learned
                      from an interface marked "notransit" will be advertised
                      on another interface marked "notransit".  Marking only a
                      single interface "notransit" has no meaning.

       accept|deny (route/mask-len [exact])+ [bidir]
                      The accept and deny commands allow rudimentary route
                      filtering.  The accept command causes mrouted to accept
                      only the listed routes on the configured interface; the
                      deny command causes mrouted to accept all but the listed
                      routes.  Only one of accept or deny commands may be used
                      on a given interface.

                      The list of routes follows the accept or deny keyword.
                      If the keyword exact follows a route, then only that
                      route is matched; otherwise, that route and any more
                      specific route is matched.  For example, deny 0/0 denys
                      all routes, while deny 0/0 exact denys only the default
                      route.  The default route may also be specified with the
                      default keyword.

                      The bidir keyword enables bidirectional route filtering;
                      the filter will be applied to routes on both output and
                      input.  Without the bidir keyword, accept and deny
                      filters are only applied on input.  Poison reverse
                      routes are never filtered out.

       Mrouted will not initiate execution if it has fewer than two enabled
       vifs, where a vif (virtual interface) is either a physical multicast-
       capable interface or a tunnel.  It will log a warning if all of its
       vifs are tunnels; such an mrouted configuration would be better
       replaced by more direct tunnels (i.e. eliminate the middle man).

       This is an example configuration for a mythical multicast router at a
       big school.

       # mrouted.conf example
       # Name our boundaries to make it easier
       name LOCAL
       name EE
       # le1 is our gateway to compsci, don't forward our
       #     local groups to them
       phyint le1 boundary EE
       # le2 is our interface on the classroom net, it has four
       #     different length subnets on it.
       # note that you can use either an ip address or an
       # interface name
       phyint boundary EE altnet
            altnet altnet
       # atm0 is our ATM interface, which doesn't properly
       #      support multicasting.
       phyint atm0 disable
       # This is an internal tunnel to another EE subnet
       # Remove the default tunnel rate limit, since this
       #   tunnel is over ethernets
       tunnel metric 1 threshold 1
            rate_limit 0
       # This is our tunnel to the outside world.
       # Careful with those boundaries, Eugene.
       tunnel metric 1 threshold 32
            boundary LOCAL boundary EE

       Mrouted responds to the following signals:

       HUP    restarts mrouted .  The configuration file is reread every time
              this signal is evoked.

       INT    terminates execution gracefully (i.e., by sending good-bye
              messages to all neighboring routers).

       TERM   same as INT

       USR1   dumps the internal routing tables to /var/tmp/mrouted.dump.

       USR2   dumps the internal cache tables to /var/tmp/mrouted.cache.

       QUIT   dumps the internal routing tables to stderr (only if mrouted was
              invoked with a non-zero debug level).

       For convenience in sending signals, mrouted writes its pid to
       /var/run/ upon startup.

       The routing tables dumped in /var/tmp/mrouted.dump look like this:

       Virtual Interface Table
        Vif  Local-Address                    Metric  Thresh  Flags
         0      subnet: 36.2/16       1       1    querier
                          pkts in: 3456
                         pkts out: 2322323

         1     subnet: 36.11/16      1       1    querier
                          pkts in: 345
                         pkts out: 3456

         2      tunnel:     3       1
                            peers: (3.255)
                       boundaries: 239.0.1/24
                                 : 239.1.2/24
                          pkts in: 34545433
                         pkts out: 234342

         3     tunnel:      3       16

       Multicast Routing Table (1136 entries)
        Origin-Subnet   From-Gateway    Metric Tmr In-Vif  Out-Vifs
        36.2                               1    45    0    1* 2  3*
        36.8            4    15    2    0* 1* 3*
        36.11                              1    20    1    0* 2  3*

       In this example, there are four vifs connecting to two subnets and two
       tunnels.  The vif 3 tunnel is not in use (no peer address). The vif 0
       and vif 1 subnets have some groups present; tunnels never have any
       groups.  This instance of mrouted is the one responsible for sending
       periodic group membership queries on the vif 0 and vif 1 subnets, as
       indicated by the "querier" flags. The list of boundaries indicate the
       scoped addresses on that interface. A count of the no. of incoming and
       outgoing packets is also shown at each interface.

       Associated with each subnet from which a multicast datagram can
       originate is the address of the previous hop router (unless the subnet
       is directly- connected), the metric of the path back to the origin, the
       amount of time since we last received an update for this subnet, the
       incoming vif for multicasts from that origin, and a list of outgoing
       vifs.  "*" means that the outgoing vif is connected to a leaf of the
       broadcast tree rooted at the origin, and a multicast datagram from that
       origin will be forwarded on that outgoing vif only if there are members
       of the destination group on that leaf.

       Mrouted also maintains a copy of the kernel forwarding cache table.
       Entries are created and deleted by mrouted.

       The cache tables dumped in /var/tmp/mrouted.cache look like this:

       Multicast Routing Cache Table (147 entries)
        Origin             Mcast-group     CTmr  Age Ptmr IVif Forwvifs
        13.2.116/22     3m   2m    -  0    1
        138.96.48/21     5m   2m    -  0    1
        128.9.160/20     3m   2m    -  0    1
        198.106.194/24     9m  28s   9m  0P

       Each entry is characterized by the origin subnet number and mask and
       the destination multicast group. The 'CTmr' field indicates the
       lifetime of the entry.  The entry is deleted from the cache table (or
       refreshed, if traffic is flowing) when the timer decrements to zero.
       The 'Age' field is the time since this cache entry was originally
       created.  Since cache entries get refreshed if traffic is flowing,
       routing entries can grow very old.  The 'Ptmr' field is simply a dash
       if no prune was sent upstream, or the amount of time until the upstream
       prune will time out.  The 'Ivif' field indicates the incoming vif for
       multicast packets from that origin.  Each router also maintains a
       record of the number of prunes received from neighboring routers for a
       particular source and group. If there are no members of a multicast
       group on any downward link of the multicast tree for a subnet, a prune
       message is sent to the upstream router. They are indicated by a "P"
       after the vif number.  The Forwvifs field shows the interfaces along
       which datagrams belonging to the source-group are forwarded. A "p"
       indicates that no datagrams are being forwarded along that interface.
       An unlisted interface is a leaf subnet with no members of the
       particular group on that subnet. A "b" on an interface indicates that
       it is a boundary interface, i.e. traffic will not be forwarded on the
       scoped address on that interface.  An additional line with a ">" as the
       first character is printed for each source on the subnet.  Note that
       there can be many sources in one subnet.  An additional line with a "<"
       as the first character is printed describing any prunes received from
       downstream dependent neighbors for this subnet and group.

       /etc/mrouted.conf        mrouted's configuration file.

       /var/run/     mrouted's PID file.

       /var/tmp/mrouted.dump    Where mrouted dumps its routing table when
                                sent a SIGUSR1.

       /var/tmp/mrouted.cache   Where mrouted dumps its forwarding cache when
                                sent a SIGUSR2.

       Note that these files are located in the following places on pre-4.4BSD

       /etc/mrouted.conf        mrouted's configuration file.

       /etc/         mrouted's PID file.

       /usr/tmp/mrouted.dump    Where mrouted dumps its routing table when
                                sent a SIGUSR1.

       /usr/tmp/mrouted.cache   Where mrouted dumps its forwarding cache when
                                sent a SIGUSR2.

       mrinfo(8), mtrace(8), map-mbone(8)

       DVMRP is described, along with other multicast routing algorithms, in
       the paper "Multicast Routing in Internetworks and Extended LANs" by S.
       Deering, in the Proceedings of the ACM SIGCOMM '88 Conference.

       Steve Deering, Ajit Thyagarajan, Bill Fenner

4.2 Berkeley Distribution                                           MROUTED(8)


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