Re: Forwarding multicast packets in Linux, for different subnets.

From: prg (rdgentry1_at_cablelynx.com)
Date: 04/26/05 

Date: 26 Apr 2005 13:43:26 -0700

smshahr...@gmail.com wrote:
> Here is my setup:
>
>
> Linux Box with two NICS
> PC1 router NIC(eth0)---NIC(eth1) router
> PC2
> 192.168.1.100 192.168.1.1 192.168.1.111 192.168.4.114 192.168.4.1
> 192.168.4.100

No way to match IPs with boxes/nics with this ASCII art :(

> Linux Box:
> ---------
> /proc/sys/net/ipv4/ip_forward
>
>
> PC1
> ----
> ping 192.168.4.1 - works
> ping 224.0.0.1 - only get reply from 192.168.1.1 and 192.168.1.111
>
>
> PC2
> ----
> ping 192.168.4.1 - works
> ping 224.0.0.1 - only get reply from 192.168.4.1 and 192.168.1.114
>
>
> The Linux box does not seem to forward multicast packets. Can someone
> shed any light on this?

Multicast is not routed like other packets...

Newer distros/kernels enable multicast, afaik...

Drivers for nics enable multicast, afaik...

To "route/forward" multicast packets requires a multicast routing
daemon listening for requests to join a multicast group. No evidence
that you're running such a multicast routing protocol daemon.

Look through this dated/abstract howto for some background:
http://www.tldp.org/HOWTO/Multicast-HOWTO.html

Look for which routing daemon(s) comes with your distro (if any) and
read up on it. Decide which kind of routing you need,
install/configure the daemon, test it, then return with specific
questions -- I can bet my private parts that you will have some;)

Would help to know just what application(s) you have in mind for
running multicast. Just on the lan? MBone?

and good luck,
prg

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