mrouted is a 3-clause BSD licensed implementation of the DVMRP multicast routing protocol. It can run on any UNIX based system, from embedded Linux systems to workstations, turning them into multicast routers with tunnel support, which can be used to cross non-multicast-aware routers.

DVMRP is a distance vector based protocol, derived from RIP, suitable for closely located multicast users in smaller networks. It simply floods all multicast streams to all routers, i.e. implicit join. This is also known as "flood and prune" since you can opt out from groups you do not want. For a detailed explanation of the protocol, consult RFC 1075.

The mrouted routing daemon was developed by David Waitzman, Craig Partridge, Steve Deering, Ajit Thyagarajan, Bill Fenner, David Thaler and Daniel Zappala. With contributions by many others.

The last release by Mr. Fenner was 3.9-beta3 on April 26 1999 and mrouted has been in "beta" status since then. Several prominent UNIX operating systems, such as AIX, Solaris, HP-UX, BSD/OS, NetBSD, FreeBSD, OpenBSD as well as most GNU/Linux based distributions have used that beta as a de facto stable release, with (mostly) minor patches for system adaptations. Over time however many dropped support, but Debian and OpenBSD kept it under their wings.

In March 2003 OpenBSD, led by the fearless Theo de Raadt, managed to convince Stanford to release mrouted under a fully free license, the 3-clause BSD license. Unfortunately, and despite the license issue being corrected by OpenBSD, in February 2005 Debian dropped mrouted as an "obsolete protocol".

For a long time the OpenBSD team remained the sole guardian of this project. In 2010 Joachim Nilsson revived mrouted on GitHub. The 3.9.x stable series represent the first releases in over a decade. Patches from all over the Internet, including OpenBSD, have been merged.

mrouted is primarily developed on Linux and should work as-is out of the box on all major distributions. Other UNIX variants should also work, but are not as thoroughly tested. For some tips and details, see the configure script.

When building mrouted from source you first need to run the configure script to generate the file config.mk. The script relies on Bourne shell standard features as well as expr and uname. Any optional mrouted features, such as --enable-rsrr are activated here as well.

Example:

./configure --enable-rsrr
make

sudo make install

The Makefile supports de facto standard environment variables such as prefix and DESTDIR for the install process. E.g., to install mrouted to /usr instead of the default /usr/local, but redirect to a binary package directory in /tmp:

VERSION=3.9.7-1 prefix=/usr DESTDIR=/tmp/mrouted-3.9.7-1 make clean install

mrouted must run as root.

For the native mrouted tunnel to work in Linux based systems, you need to have the "ipip" kernel module loaded or as built-in:

modprobe ipip

mrouted reads its configuration file from /etc/mrouted.conf. You can override the default by specifying an alternate file when invoking mrouted:

mrouted -f /path/file.conf

mrouted can be reconfigured at runtime like any regular UNIX daemon, simply send it a SIGHUP to activate changes to the configuration file. The PID is saved automatically to the file /var/run/mrouted.pid for your scripting needs.

By default, mrouted configures itself to act as a multicast router on all multicast capable interfaces, excluding loopback. Therefore, you do not need to explicitly configure mrouted, unless you need to setup tunnel links, change the default operating parameters, disable multicast routing over a specific physical interfaces, or have dynamic interfaces.

For more help, see the man page.

The basic functionality has been tested thoroughly over the years, but that does not mean mrouted is bug free. Please report bugs, feature requests, patches and pull requests in the GitHub issue tracker

Routing Support for Resource Reservations (RSRR) is required for running RSVP and was contributed by Daniel Zappala daniel@isi.edu.

RSRR allows RSVP to query mrouted for its routing entry for a particular source-group pair. Using the routing entry and the IP_MULTICAST_VIF socket call, RSVP can forward distinct control messages out each outgoing interface. This version of mrouted supports RSRR messages using a Unix datagram socket.

RSRR currently includes two pairs of query-reply messages. RSVP sends an Initial Query when it starts. Mrouted responds with an Initial Reply that includes the set of vifs it is using, flagging those that are administratively disabled. When RSVP needs the routing entry for a source-group pair, it sends a Route Query. Mrouted responds with a Route Reply that includes the incoming vif and outgoing vifs for the source-group pair.

RSVP may request route change notification by setting the notification bit in the Route Query. If mrouted can provide route change notification for the source-group pair, it sets the notification bit in its Route Reply. When the routing entry for the source-group pair changes, mrouted sends an unsolicited Route Reply containing the new routing information.