380 lines
13 KiB
Groff
380 lines
13 KiB
Groff
'\"COPYRIGHT 1989 by The Board of Trustees of Leland Stanford Junior University.
|
|
.Dd March 25, 1995
|
|
.Dt MROUTED 8
|
|
.Os FreeBSD 2.0
|
|
.Sh NAME
|
|
.Nm mrouted
|
|
.Nd IP multicast routing process
|
|
.Sh SYNOPSIS
|
|
.Nm mrouted
|
|
.Op Fl p
|
|
.Op Fl c Ar config
|
|
.Op Fl d Ar debuglevel
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
program
|
|
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 Multicasting.
|
|
.Pp
|
|
.Nm
|
|
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.
|
|
.Pp
|
|
In order to support multicasting among subnets that are separated by (unicast)
|
|
routers that do not support IP multicasting,
|
|
.Nm
|
|
includes support for
|
|
.Dq tunnels ,
|
|
which are virtual point-to-point links between pairs of
|
|
.Nm
|
|
programs 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. By default, the packets are encapsulated using the
|
|
IP-in-IP protocol (IP protocol number 4). Older versions of
|
|
.Nm
|
|
tunneled using IP source routing, which puts a heavy load on some
|
|
types of routers.
|
|
This version supports IP source route tunnelling only for backwards
|
|
compatibility.
|
|
.Pp
|
|
The tunnelling mechanism allows
|
|
.Nm
|
|
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.
|
|
.Nm
|
|
suffers from the well-known scaling problems of any distance-vector
|
|
routing protocol, and does not (yet) support hierarchical multicast routing.
|
|
.Pp
|
|
.Nm
|
|
handles multicast routing only; there may or may not be unicast routing
|
|
software running on the same machine as
|
|
.Nm mrouted .
|
|
With the use of tunnels, it
|
|
is not necessary for
|
|
.Nm
|
|
to have access to more than one physical subnet
|
|
in order to perform multicast forwarding.
|
|
.Pp
|
|
If no
|
|
.Fl d
|
|
option is given, or if the debug level is specified as 0,
|
|
.Nm
|
|
detaches from its controlling terminal. Otherwise, it remains attached to the
|
|
terminal and responsive to signals.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
program accepts the following command-line options:
|
|
.Bl -tag -width XXXdebuglevel
|
|
.It Fl c Ar config
|
|
This option specifies an alternate configuration file location as
|
|
.Ar config .
|
|
The default location is
|
|
.Pa /etc/mrouted.conf .
|
|
.It Fl d Ar debuglevel
|
|
This option sets the debuging level to
|
|
.Ar debuglevel .
|
|
Regardless of the debug level,
|
|
.Nm
|
|
always writes warning and error messages to the system
|
|
log demon. Non-zero debug levels have the following effects:
|
|
.Bl -tag -width "level 3"
|
|
.It level 1
|
|
all syslog'ed messages are also printed to stderr.
|
|
.It level 2
|
|
all level 1 messages plus notifications of
|
|
.Dq significant
|
|
events are printed to stderr.
|
|
.It level 3
|
|
all level 2 messages plus notifications of all packet
|
|
arrivals and departures are printed to stderr.
|
|
.El
|
|
.It Fl p
|
|
This option disables pruning of uninterested links in the multicast
|
|
distribution tree.
|
|
.El
|
|
.Sh CONFIGURATION
|
|
.Nm
|
|
automatically configures itself to forward on all multicast-capable
|
|
interfaces; i.e., interfaces that have the
|
|
.Dv IFF_MULTICAST
|
|
flag set (excluding the loopback), and it finds other
|
|
.Nm
|
|
programs directly reachable via those interfaces. To override the
|
|
default configuration, or to add tunnel links to other
|
|
.Nm
|
|
programs, configuration commands may be placed in
|
|
.Pa /etc/mrouted.conf
|
|
(or an alternate location can be specified using the
|
|
.Fl c
|
|
option).
|
|
There are four types of configuration commands:
|
|
.Bd -literal
|
|
|
|
phyint <local-addr> [disable] [metric <m>]
|
|
[threshold <t>] [rate_limit <b>]
|
|
[boundary <scoped-addr>/<mask-len>]
|
|
|
|
tunnel <local-addr> <remote-addr> [metric <m>]
|
|
[threshold <t>] [srcrt] [rate_limit <b>]
|
|
[boundary <scoped-addr>/<mask-len>]
|
|
|
|
cache_lifetime <ct>
|
|
|
|
pruning <off/on>
|
|
|
|
.Ed
|
|
.Pp
|
|
One note about the configuration commands--all the phyint and tunnel
|
|
command options must be on a single line except for the boundary option
|
|
which may begin on a separate line. A single phyint or tunnel command may
|
|
have multiple boundary options.
|
|
.Pp
|
|
The phyint command can be used to disable multicast routing on the physical
|
|
interface identified by local IP address <local-addr>, or to associate a
|
|
non-default metric or threshold with the specified physical interface.
|
|
The local IP address <local-addr> may be alternatively replaced by the
|
|
interface name (e.g., le0) for the phyint command only.
|
|
Phyint commands must precede tunnel commands.
|
|
.Pp
|
|
The tunnel command can be used to establish a tunnel link between local
|
|
IP address <local-addr> and remote IP address <remote-addr>, and to associate
|
|
a non-default metric or threshold with that tunnel. The tunnel must be set
|
|
up in the mrouted.conf files of both routers before it can be used.
|
|
For backwards compatibility with older
|
|
.Nm
|
|
programs, the srcrt keyword specifies
|
|
encapsulation using IP source routing.
|
|
.Pp
|
|
The cache_lifetime is a value that determines the amount of time that a
|
|
cached multicast route stays in kernel before timing out. The value of this
|
|
entry should lie between 300 (5 min) and 86400 (1 day). It defaults to 300.
|
|
.Pp
|
|
The pruning <off/on> option is provided for
|
|
.Nm
|
|
to act as a non-pruning router. It is also possible to start
|
|
.Nm
|
|
in a non-pruning mode using the
|
|
.Fl p
|
|
flag on the command line. It is expected that a router would be
|
|
configured in this manner for test purposes only. The default mode is
|
|
pruning enabled.
|
|
.Pp
|
|
The metric is the
|
|
.Dq cost
|
|
associated with sending 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
|
|
.Nm
|
|
cannot route along paths with a sum of metrics greater
|
|
than 31.
|
|
.Pp
|
|
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 1.) The default threshold is 1.
|
|
.Pp
|
|
In general, all
|
|
.Nm mrouted
|
|
programs connected to a particular subnet or tunnel should
|
|
use the same metric and threshold for that subnet or tunnel.
|
|
.Pp
|
|
The rate_limit option allows the network administrator to specify a
|
|
certain bandwidth in Kbits/second which would be allocated to multicast
|
|
traffic.
|
|
.Pp
|
|
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.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
program
|
|
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
|
|
.Nm
|
|
configuration would be better replaced by more
|
|
direct tunnels (i.e., eliminate the middle man).
|
|
.Sh SIGNALS
|
|
The
|
|
.Nm
|
|
program responds to the following signals:
|
|
.Bl -tag -width SIGTERMx
|
|
.It Dv SIGHUP
|
|
restarts
|
|
.Nm mrouted .
|
|
The configuration file is reread every time this signal is evoked.
|
|
.It Dv SIGINT
|
|
terminates execution gracefully (i.e., by sending
|
|
good-bye messages to all neighboring routers).
|
|
.It Dv SIGTERM
|
|
same as
|
|
.Dv SIGINT
|
|
.It Dv SIGUSR1
|
|
dumps the internal routing tables to
|
|
.Pa /var/tmp/mrouted.dump .
|
|
.It Dv SIGUSR2
|
|
dumps the internal cache tables to
|
|
.Pa /var/tmp/mrouted.cache .
|
|
.It Dv SIGQUIT
|
|
dumps the internal routing tables to stderr (only if
|
|
.Nm
|
|
was invoked with a non-zero debug level).
|
|
.El
|
|
.Sh EXAMPLE
|
|
The routing tables look like this:
|
|
.Bd -literal
|
|
|
|
Virtual Interface Table
|
|
Vif Local-Address Metric Thresh Flags
|
|
0 36.2.0.8 subnet: 36.2 1 1 querier
|
|
groups: 224.0.2.1
|
|
224.0.0.4
|
|
pkts in: 3456
|
|
pkts out: 2322323
|
|
|
|
1 36.11.0.1 subnet: 36.11 1 1 querier
|
|
groups: 224.0.2.1
|
|
224.0.1.0
|
|
224.0.0.4
|
|
pkts in: 345
|
|
pkts out: 3456
|
|
|
|
2 36.2.0.8 tunnel: 36.8.0.77 3 1
|
|
peers: 36.8.0.77 (2.2)
|
|
boundaries: 239.0.1
|
|
: 239.1.2
|
|
pkts in: 34545433
|
|
pkts out: 234342
|
|
|
|
3 36.2.0.8 tunnel: 36.6.8.23 3 16
|
|
|
|
Multicast Routing Table (1136 entries)
|
|
Origin-Subnet From-Gateway Metric In-Vif Out-Vifs
|
|
36.2 1 0 1* 2 3*
|
|
36.8 36.8.0.77 4 2 0* 1* 3*
|
|
36.11 1 1 0* 2 3*
|
|
.
|
|
.
|
|
.
|
|
|
|
.Ed
|
|
.Pp
|
|
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
|
|
.Nm
|
|
is the one responsible for sending periodic group
|
|
membership queries on the vif 0 and vif 1 subnets, as indicated by the
|
|
.Dq querier
|
|
flags. The list of boundaries indicate the scoped addresses on that
|
|
interface. A count of the number of incoming and outgoing packets is
|
|
also shown at each interface.
|
|
.Pp
|
|
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 incoming vif for multicasts from that origin, and a list of
|
|
outgoing vifs.
|
|
.Dq Li \&*
|
|
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.
|
|
.Pp
|
|
.Nm
|
|
also maintains a copy of the kernel forwarding cache table. Entries
|
|
are created and deleted by
|
|
.Nm mrouted .
|
|
.Pp
|
|
The cache tables look like this:
|
|
.Bd -literal
|
|
|
|
Multicast Routing Cache Table (325 entries)
|
|
Origin-Subnet Mcast-group CTmr IVif Prcv# Psnt Forwvifs
|
|
134.207.7 224.2.140.239 300 1 0 0 2
|
|
138.15.103 224.2.203.214 295 1 2 P 0p 2p
|
|
128.237.0 224.2.253.119 290 1 1 0 2p
|
|
129.215.200 224.2.207.48 40 1 1 0p 2
|
|
36.77.14 239.0.1.234 345 2b
|
|
|
|
.Ed
|
|
.Pp
|
|
Each entry is characterized by the origin subnet number and the
|
|
destination multicast group. The
|
|
.Dq CTmr
|
|
field indicates the lifetime
|
|
(in seconds) of the entry. The entry is deleted from the cache table
|
|
when the timer decrements to zero. The
|
|
.Dq 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 neighbouring
|
|
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
|
|
.Dq Li \&P
|
|
in the
|
|
.Dq Psnt
|
|
field. The
|
|
.Dq Forwvifs
|
|
field shows the
|
|
interfaces along which datagrams belonging to the source-group are
|
|
forwarded. A
|
|
.Dq Li \&p
|
|
indicates that no datagrams are being forwarded along
|
|
that interface. An unlisted interface is a leaf subnet with are no
|
|
members of the particular group on that subnet. A
|
|
.Dq Li \&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.
|
|
.Sh FILES
|
|
.Bl -tag -compact -width /var/tmp/mrouted.cache
|
|
.It Pa /etc/mrouted.conf
|
|
default configuration file
|
|
.It Pa /var/tmp/mrouted.cache
|
|
kernel forwarding cache dump file
|
|
.It Pa /var/tmp/mrouted.dump
|
|
routing table dump file
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr map-mbone 8 ,
|
|
.Xr mrinfo 8 ,
|
|
.Xr mtrace 8
|
|
.Rs
|
|
.%A "S. Deering"
|
|
.%B "Proceedings of the ACM SIGCOMM '88 Conference"
|
|
.%T "Multicast Routing in Internetworks and Extended LANs"
|
|
.Re
|
|
.Sh AUTHORS
|
|
Steve Deering & Ajit Thyagarajan
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
program first appeared in
|
|
.Tn FreeBSD
|
|
2.0.
|