[KLUG Members] multicast

[Peter Buxton]

Okay. I just went back and read all of your posts, John. I have a much
better grip on just who said what when. On 14 August you said you have
two subnets and a third to a foreign group of subnets across a T1
router/CSU/DSU. I take it this router doesn't do multicast routing? And
as I understand it, you don't have any multicast connectivity between
the three? Correct?

Is this a different problem than the 6 August post:

> We started testing it between LANs using multicast routers.  Linux
> reports that the computer is joining the group, the routers show that
> the host on the port joined a group so it joins the group. but the
> traffic doesn't seem to flow, at least not as expected. We played with
> it for over an hour last week with no packets getting through and then
> suddently they did and everything worked with no explaination.
> Yesturday we tried again and again there was nothing.

Can you post the netfilter script on the gateway between your networks
and the foreign nets?

Okay, Rusty has the four network segments.

> I have a system with 4 network segments that are connected with a
> single Linux firewall system... I need to get multicast info from one
> side of the system to the others.... I have done some research ... it
> seems like if the kernel is setup to support it (not sure if the stock
> SuSE 8.2 kernel is) then I might only have to put in a static route.

No, not with route, I don't think. Remember that the route command
simply establishes the internal, "Where do I send this next outgoing
packet?" routing table. It is very different than iptables.

ip route might do what you want, but the LARTC document says you need
kernel-side:

CONFIG_IP_MULTICAST:
CONFIG_IP_MROUTE:
 CONFIG_IP_PIMSM_V1: for the PIM-SM/DIM protocols
 CONFIG_IP_PIMSM_V2: ditto

Also, the userspace Zebra, mrouted or pimd is needed to route these
packets.  Which of these are you using? Or you, John? They are used
mainly by MBONE hosts, not LAN gateways. Are your network segments
joined by iptables or ip route?

> I have ip forwarding turned on.  I am using iptables to perform
> firewalling and nat'ing to the one side that ultimately goes to the
> Internet....   I think I just need to add the ip route command.  Not
> sure which device to use though... the one that has the multicast
> server on it??? 

That would be most convenient. As long as you are relaying all the
multicast traffic along all the segments, you can just add one interface
as a multicast receiver -- as opposed to forwarder.

However, I think you need to add iptables commands if your four segments
are being joined by iptables, as well.

iptables -A FORWARD -m pkttype --pkt-type multicast -j ACCEPT

-- 
-16
OS/2? Hah. I've got Linux. What a cool name. -- l.torvalds