Configuring Multicast routing on Linux 2.4.x

Configuring Multicast routing on Linux 2.4.x

Post by Nirmal Vuppulu » Wed, 31 Jul 2002 08:25:33


I know this issue has been dealt with quite a lot in these pages but
please listen me out.

Problem:  Do I need mrouted or pimd for doing mcast routing with a
2.4.x kernel?

After reading the "Multicast Routing" section of the "Linux 2.4
Advanced Routing HOWTO", I concluded that I need pimd or mrouted or
such to actually do mcast routing, even though I enable IP Multicast
routing and PIM-SM v1 and PIM-SM v2 support when doing "make
menuconfig".  Specifically, the following line mentions something
about it:

"In the Linux kernel, you will notice that these options don't appear.
This is because the protocol itself is handled by a routing
application, such as Zebra, mrouted, or pimd. However, you still have
to have a good idea of which you're going to use, to select the right
options in the kernel. "

So, when I try to download "pimd" from the USC website, I read
something like:

"Linux kernel has PIM support. However, kernels historically older
  2.2.11 or 2.3.6 need a small fix. "

That has got me confused.  Any clarifications?  Any information would
be greatly appreciated.  Thanks a bunch,



1. Linux 2.4 and Multicast Tunneling

I am trying to figure out how to connect my machine to the MBone.
I am running the 2.4.2 kernel on a Red Hat 7.0 i686, and this is
where I am so far:

* My kernel supports multicasting and advanced routing:


* My host responds to ping  My gateway (a SDSL modem/router
  made by Netopia for Covad), however, does not, nor does it respond
  to ping  Therefore, I believe I must set up a tunnel to
  a host on the MBone in order to receive multicast datagrams from the
  outside world.

* I have read

* I know about mrouted, have downloaded the Linux version from as instructed in the
  Multicast HOWTO, and have successfully compiled it after messing
  around with the #includes a bit.  But after looking at the HOWTO
  documents and my kernel configuration, I began to wonder if the
  functionality of mrouted had been partially or fully absorbed
  into the Linux kernel.

* I have read
  Unfortunately, Section 7 (Multicast routing) says:

  "FIXME: Editor Vacancy! (somebody is working on it, though)"

This is what I would like to know before I go further with mrouted:

* Is mrouted superfluous if I have the 2.4 kernel or does it provide
  some capability (e.g. multicast tunneling through a virtual interface)
  that the kernel does not?

* Suppose I know the IP address of a nearby multicast router and would
  like to set up a tunnel from my machine to that router (a tunnel to
  the MBone), so that I may receive multicast datagrams in spite of the
  fact that intervening routers are ignorant of multicast routing protocols.
  Can I set up an interface to accomplish this task without having to
  run mrouted?  If so, how?

Dave Bailey

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