[KLUG Members] multicast

[John Pesce]

FYI. On my Linux box I have more details. Actually, the new config is LAN 
A on eth0, LAN B on eth2, and T1 on eth1. I currently have the multicast 
app running on machines on LAN A and LAN B and the packets arn't crossing. 
If I ping -c 2 224.0.0.1 I only get responses from machines on eth2.

[root@rts linux-2.4]# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.7.31.0       10.7.35.1       255.255.255.0   UG    0      0        0 eth1
192.168.3.0     *               255.255.255.0   U     0      0        0 eth0
192.168.2.0     *               255.255.255.0   U     0      0        0 eth2
10.7.36.0       10.7.35.1       255.255.255.0   UG    0      0        0 eth1
10.7.32.0       10.7.35.1       255.255.255.0   UG    0      0        0 eth1
10.7.33.0       10.7.35.1       255.255.255.0   UG    0      0        0 eth1
10.7.34.0       10.7.35.1       255.255.255.0   UG    0      0        0 eth1
10.7.35.0       *               255.255.255.0   U     0      0        0 eth1
169.254.0.0     *               255.255.0.0     U     0      0        0 eth2
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
224.0.0.0       *               240.0.0.0       U     0      0        0 eth2
224.0.0.0       *               240.0.0.0       U     0      0        0 eth1
224.0.0.0       *               240.0.0.0       U     0      0        0 eth0
default         192.168.3.1     0.0.0.0         UG    0      0        0 eth0

[root@rts linux-2.4]# ip link show
1: lo: <LOOPBACK,UP> mtu 16436 qdisc noqueue
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 100
    link/ether 00:a0:c9:f1:87:32 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 100
    link/ether 00:a0:c9:8e:cd:65 brd ff:ff:ff:ff:ff:ff
4: eth2: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 100
    link/ether 00:a0:c9:8e:c3:f7 brd ff:ff:ff:ff:ff:ff

[root@rts linux-2.4]# ping -c 2 224.0.0.1
PING 224.0.0.1 (224.0.0.1) 56(84) bytes of data.
64 bytes from 192.168.2.3: icmp_seq=1 ttl=64 time=0.280 ms
64 bytes from 192.168.2.5: icmp_seq=1 ttl=64 time=0.297 ms (DUP!)

The multicast group I'm using is 224.5.13.71



On Wed, 3 Sep 2003, John Pesce wrote:

> Hi Peter,
> 
> I think the John posts from 14 Auguest refer to me :)
> 
> Mine is similiar to the new thread that was started today.
> This is my case:
> 
> I have LAN A and LAN B connected to a Linux box as eth0 and eth1 with 
> IP_FORWARD turned on to pass TCP/IP traffic between them.
> 
> Yesturday the T1 in question came online and at the moment I plugged the 
> Ethernet port on the Cisco conencted to it into a new eth2 on my Linux 
> box. 
> 
> On the other side of the T1 are more T1s connecting serveral LANs. All the 
> T1 routers have PIM-DM turned on. My my point of view the address of the 
> ethernet port on the Cisco is 10.7.35.1 and will be the gateway to 
> everything else. I added static routes to those networks on my Linux box.
> I don't have direct control over those Cisco routers.
> 
> So, the deal is I have a multicast program that will be run on Linux boxes 
> on all the above mentioned LANs joining the same multicast group.
> 
> I need to forward pass the multicast traffic through the Linux box so 
> everyone can talk while running a firewall on the Linux box to protect my 
> two LANs from everything over the T1 except the multicast traffic.
> 
> I looked at the kernel config on my RH9 install and multicast forwarding 
> is enabled by default. I just need to know how to get the multicast 
> flowing through the firewall.
> 
> John
> 
> On Wed, 3 Sep 2003, Peter Buxton wrote:
> 
> > 
> > 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
> > 
> > 
> 
> 

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|                                    Software Engineer               |
|       John Pesce          o     o  Air Traffic Management Lab      |
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