Since I create few VLAN at work, the servers and (NOC) workstations are no longer in the same IP subnet (I don't even understand how the previous sys/net admin can leave servers and workstations in the same LAN). So, a java admin ask me why he can't setup a weblogic cluster with one node in our LAN (the NOC one), and one node in the LAN server. I just told him "hold on few mintes". Well, ok, few hours after, it still doesn't working... But It's now ok, I use the following config : ! interface Vlan1 ip address 192.168.1.4 255.255.255.0 ip pim dense-mode ip igmp join-group 232.168.34.65 ip igmp join-group 237.0.0.9 ntp multicast key 1 end ! interface Vlan34 ip address 192.168.34.1 255.255.255.0 ip helper-address 192.168.1.6 ip pim dense-mode ip igmp join-group 232.168.34.65 ip igmp join-group 237.0.0.9 ntp multicast key 1 end ! ip multicasting-routing ! But **the more important point is the TTL** which is set by the multicast application. IT **MUST BE GREATER** than one (1) if you want forwarding multicast. Example : % sudo udp-sender --file docs/CompilingBinaryFilesUsingACompiler.pdf --mcast-all-addr 232.168.34.65 --ttl 64 Udp-sender 2004-05-31 Using mcast address 232.168.34.65 UDP sender for docs/CompilingBinaryFilesUsingACompiler.pdf at 192.168.34.65 on eth0 Broadcasting control to 232.168.34.65 New connection from 192.168.1.50 (#0) 00000019 Ready. Press any key to start sending data. Starting transfer: 00000019 bytes= 67 278 re-xmits=000000 ( 0.0%) slice=0202 67 278 - 0 Transfer complete. Disconnecting #0 (192.168.1.50) % sudo udp-receiver --ttl 64 --mcast-all-addr 232.168.34.65 --file /tmp/output Udp-receiver 2004-05-31 UDP receiver for /tmp/output at 192.168.1.50 on eth0 received message, cap=00000019 Connected as #0 to 192.168.34.65 Listening to multicast on 232.168.34.65 Press any key to start receiving data! Sending go signal 1 Success 0 bytes= 67 278 ( 1.05 Mbps) 67 278 Transfer complete. As you can notice, I use udp-receiver / udp-sender - available [[http://alain.knaff.lu/udpcast/|here]], or maybe with your distrib (Debian include it) - to test the multicast. I just wondering why it doesn't work if the Cisco is not a member of the group, I probably need to check docs again and again.