mrouted.conf File

Purpose

Default configuration information for the multicast routing daemon mrouted.

Description

The /etc/mrouted.conf configuration file contains entries that provide configuration information used by mrouted. You can specify any combination of these entries in this file.

The file format is free-form; white space and newline characters are not significant. The phyint, tunnel, and name entries can be specified more than once. The boundary and altnet values can be specified as many times as necessary.

The following entries and their options can be used in the mrouted.conf file:

phyint local_addr [disable] [metric m] [threshold t] [rate_limit b] [boundary

(boundary_name | scoped_addr/mask_len)] [altnet network/mask_len]

The phyint entry can be used to disable multicast routing on the physical interface identified by the local IP address local_addr, or to associate a non-default metric or threshold with the specified physical interface. The local IP address can be replaced by the interface name (for example, le0). If a physical interface is attached to multiple IP subnets, describe each additional subnet with the altnet option. Phyint entries must precede tunnel entries.

The options for the phyint entry and the actions they generate are as follows:

local_addr: Specifies the local address, using either an IP address or an interface name, such as en0.
disable: Disables multicast routing on the physical interface identified by local_addr.
metric m: Specifies the "cost" associated with sending a datagram on the given interface or tunnel. This option can be used to influence the choice of routes. The default value of m is 1. Metrics should be kept as small as possible, because mrouted cannot route along paths with a sum of metrics greater than 31.
threshold t: Specifies the minimum IP time-to-live (TTL) required for a multicast datagram to be forwarded to the given interface or tunnel. This option controls the scope of multicast datagrams. (The TTL of forwarded packets is compared only to the threshold, it is not decremented by the threshold.) The default value of t is 1. In general, all mrouted daemons connected to a particular subnet or tunnel should use the same metric and threshold for that subnet or tunnel.
rate_limit b: Specifies a bandwidth in Kilobits/second, which is allocated to multicast traffic. The default value of b is 500 Kbps on tunnels, and 0 (unlimited) on physical interfaces.
boundary boundary_name|scoped_addr/mask_len: Configures an interface as an administrative boundary for the specified scoped address. Packets belonging to this address are not forwarded on a scoped interface. The boundary option accepts either a boundary name or a scoped address and mask length. The boundary_name is the name assigned to a boundary with the name entry. The scoped_addr value is a multicast address. The mask_len value is the length of the network mask.
altnet network/mask_len: Specifies an additional subnet (network) attached to the physical interface described in the phyint entry. mask_len is the length of the network mask.

tunnel local_addr remote_addr [metric m] [threshold t] [rate_limit b] [boundary {boundary_name | scoped_addr/mask_len}] [altnet network/mask_len]

The tunnel entry can be used to establish a tunnel link between the local IP address ( local_addr ) and the remote IP address ( remote_addr ), and to associate a non-default metric or threshold with that tunnel. The local IP address can be replaced by the interface name (for example, le0 ). The remote IP address can 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. The phyint entry can be used to disable multicast routing on the physical address interface identified by the local IP address local_addr , or to associate a non-default metric or threshold with the specified physical interface. The local IP address can be replaced by the interface name (for example, le0 ). If a physical interface is attached to multiple IP subnets, describe each additional subnet with the altnet option. Phyint entries must precede tunnel entries.

For a description of the options used with the tunnel entry, see the preceding option descriptions in the phyint entry.

cache_lifetime ct

The cache_lifetime entry determines the amount of time that a cached multicast route stays in the kernel before timing out. The value of ct is in seconds, and should lie between 300 (five minutes) and 86400 (one day). The default value is 300 seconds .

pruning state

The pruning entry enables mrouted to act as a non-pruning router. The value of state can be either on or off . You should configure your router as a non-pruning router for test purposes only. The default mode is on , which enables pruning.

name boundary_name scoped_addr/mask-len

The name entry lets you assign names to boundaries to make it easier to configure. The boundary option on the phyint and tunnel entries accepts either a boundary name or a scoped address. The boundary_name is the name you want to give to the boundary. The scoped_addr value is a multicast address. The mask_len value is the length of the network mask.

Example

This example shows a configuration for a multicast router at a large school.

#
# mrouted.conf
#
# Name our boundaries to make it easier
name LOCAL 239.255.0.0/16 name EE 239.254.0.0/16
#
# le1 is our gateway to compsci, don't forward our
#   local groups to them
phyint le1 boundary LOCAL
#
# le2 is our interface on the classroom network,
#   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 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 192.168.5.4 192.168.55.101 metric 1 threshold 1
  rate_limit 0
# This is our tunnel to the outside world.
tunnel 192.168.5.4 10.11.12.13 metric 1 threshold 32
  boundary LOCAL boundary EE