|Print a help message and exit.|
|If an interface does not yet exist, print a warning and continue. Useful with VPN and other dynamic interfaces. However, mrouted must be restarted to start listening on such interfaces, if they did not exist when mrouted was started.|
|Assume all interfaces are disabled unless explicitly enabled with phyint enable|
|Run in foreground, do not detach from the calling terminal.|
|Specify an alternative configuration file, default /etc/mrouted.conf|
detaches from the invoking terminal.
If this option is specified,
it runs in foreground of the starting terminal and responds to signals.
is given with no argument, the debug level defaults to
igmp, cache, interface, groups, prunes, routes and peers.
Regardless of the debug level, mrouted always writes warning and error messages to the system log daemon. Debug levels have the following effects:
|Debug inbound/outbout packets|
|Pruning operations, or pruned routes|
|Detailed routing information|
|cache||Debug routing cache|
|Show interface, or vif, debug messages|
|Debug group memberships|
|Multicast traceroute information|
|igmp||Debug IGMP messages|
|icmp||Debug ICMP messages|
|rsrr||Debug RSRR messages|
|-p||Start mrouted in a non-pruning mode. This was previously used in routers for test purposes only. However, this is no longer supported and this option is only kept for compatibility reasons.|
|Show state of VIFs and multicast routing tables. This command sends SIGUSR1 to a running mrouted, waits for the dump file to be updated, and then displays the result on stdout.|
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 mrouted directly reachable via those interfaces. To override the default configuration, or to add tunnel links to other mrouted, configuration commands may be placed in /etc/mrouted.conf. There are five types of configuration commands:
cache_lifetime <SEC> name boundary-name | scoped-addr / mask-len phyint local-addr [ altnet network / mask-len ] [ boundary boundary-name | scoped-addr / mask-len ]
[disable | enable]
pruning [off | on] tunnel local-addr remote-addr [ boundary boundary-name | scoped-addr / mask-len ]
The file format is free-form: whitespace (including newlines) is not significant. The boundary option can accept either a name or a boundary; the boundary and altnet options may be specified as many times as necessary.
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.
The name option assigns names to boundaries to make configuration easier.
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 replaced by the interface name (e.g. le0). If a phyint is attached to multiple IP subnets, describe each additional subnet with the altnet keyword. Phyint commands must precede tunnel commands.
The pruning option is provided for mrouted to act as a non-pruning router. This is no longer supported and the configuration option is only kept for compatibility reasons.
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 local IP address local-addr may be replaced by the interface name (e.g. le0). The remote IP address remote-addr may be replaced by a host name, if and only if the host name has a single IP address associated with it. The tunnel must be set up in the mrouted.conf files of both routers before it can be used.
boundary 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.
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 metric defaults to 1. Metrics should be kept as small as possible, because mrouted cannot route along paths with a sum of metrics greater than 31.
rate_limit allows the network administrator to specify a certain bandwidth in kbps which would be allocated to multicast traffic. It defaults to 500 kbps on tunnels, and 0 (unlimited) on physical interfaces.
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.
In general, all mrouted connected to a particular subnet or tunnel should use the same metric and threshold for that subnet or tunnel.
mrouted will not initiate execution if it has fewer than two enabled virtual interfaces (vifs), where a vif 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 184.108.40.206/16 name EE 220.127.116.11/16
# le1 is our gateway to compsci, dont 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 172.16.12.38 boundary EE altnet 172.16.15.0/26 altnet 172.16.15.128/26 altnet 172.16.48.0/24
# atm0 is our ATM interface, which doesnt 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 192.168.5.4 192.168.55.101 metric 1 threshold 1 rate_limit 0
# This is our tunnel to the outside world. # Careful with those boundaries, Eugene. tunnel 192.168.5.4 10.11.12.13 metric 1 threshold 32 boundary LOCAL boundary EE
mrouted responds to the following signals:
HUP Restarts mrouted. The configuration file is reread when SIGHUP is received. INT Terminates execution gracefully (i.e. by sending good-bye messages to all neighboring routers). TERM The same as INT. USR1 Dumps the internal routing tables to /var/run/mrouted/mrouted.dump. USR2 Dumps the internal cache tables to /var/run/mrouted/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 process ID to /var/run/mrouted.pid upon startup.
The routing tables look like this:Virtual Interface Table Vif Local-Address Metric Thresh Flags 0 18.104.22.168 subnet: 36.2 1 1 querier groups: 22.214.171.124 126.96.36.199 pkts in: 3456 pkts out: 2322323
1 188.8.131.52 subnet: 36.11 1 1 querier groups: 184.108.40.206 220.127.116.11 18.104.22.168 pkts in: 345 pkts out: 3456
2 22.214.171.124 tunnel: 126.96.36.199 3 1 peers: 188.8.131.52 (2.2) boundaries: 239.0.1 : 239.1.2 pkts in: 34545433 pkts out: 234342
3 184.108.40.206 tunnel: 220.127.116.11 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 18.104.22.168 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 number 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 look like this:Multicast Routing Cache Table (147 entries) Origin Mcast-group CTmr Age Ptmr IVif Forwvifs 13.2.116/22 22.214.171.124 3m 2m - 0 1 >126.96.36.199 188.8.131.52 138.96.48/21 184.108.40.206 5m 2m - 0 1 >220.127.116.11 128.9.160/20 18.104.22.168 3m 2m - 0 1 >22.214.171.124 198.106.194/24 126.96.36.199 9m 28s 9m 0P >188.8.131.52
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 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.
map-mbone(8), mrinfo(8), mtrace(8), pimd(8)
.Rs Multicast Routing in Internetworks and Extended LANs
.An David Waitzman ,
.An Craig Partridge ,
.An Steve Deering ,
.An Ajit Thyagarajan ,
.An Bill Fenner ,
.An David Thaler , and
.An Daniel Zappala . With contributions by many others.