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I'm trying to install Oracle Grid Infrastructure on two machines. Their documentation states:

You must enable multicasting for the cluster on the IP address subnet ranges and

So I ran:

route add -net dev eth2
route add -net dev eth2

route -n produces:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface   U     0      0        0 eth2   U     0      0        0 eth2
# and others

An ifconfig eth2 shows, among other things, UP BROADCAST RUNNING MULTICAST.

However, when I run their multicast test utility, it fails me:

Test for Multicast address
Sep  3 19:40:39 | Multicast Failed for eth2 using address

Test for Multicast address
Sep  3 19:41:10 | Multicast Failed for eth2 using address

What am I doing wrong?

share|improve this question
Did you open the necessary ranges in your firewall? – Michael Hampton Sep 4 '12 at 1:56
@MichaelHampton I don't think I have a firewall enabled. How would I know if I did? iptables --list doesn't give me anything. – NullUser Sep 4 '12 at 2:28
Is multicast enabled on the switch/router where your machines are connected to? – Nils Sep 7 '12 at 20:58

What's the output of netstat -gn?

By default, your multicast joins are going to go out of the lowest-numbered interface cough, eth0. Since you're attempting to do this via eth2, you're going to need another step to establish connectivity.

Does the test utility provide a means of specifying the interface? If so, you'll need to explicitly state "eth2". If that is not an option, you can add another static route to make sure your multicast traffic uses that interface.

Something like:

route add -net netmask dev eth2 (route all multicast through eth2)

Try that...

If it all works, be sure to make everything persistent by creating a /etc/sysconfig/network-scripts/route-eth2 file with your static routes.


If you have the ability to select interfaces in your application, then you DO NOT need any static routes on your interfaces. It would be up to the Oracle test utility to handle IGMP.

Try that first...

If that does not work, please verify if multicast is enabled on the network switch that the systems are connected to. What type of switches are they? I can give more detail instructions based on the switch model/type. If Cisco, for instance...

sh ip igmp snooping
sh run | i multicast-routing

Following that, there seems to be a known bug related to this product. Are you certain that you're fully-patched? It appears to be an unpublished patch, so you may have to go to Oracle to resolve this if everything else is in place.

See: Grid infrastructure multicast issue - Oracle Bug 9974223

share|improve this answer
Here's the output of netstat -gn: ; and yes, the utility allows me to specify the interface (I'm using eth2) – NullUser Sep 4 '12 at 2:30
@nulluser Yeah, joins going out of eth0, probably. You didn't answer my question about whether the test utility allows you to specify an interface. That makes a difference! – ewwhite Sep 4 '12 at 2:35
It does. I'm specifying eth2. – NullUser Sep 4 '12 at 2:40
Hmm... Remove the route statements you have, then re-add them. Maybe add the one I specified first. Try that. If it doesn't work, then we'd need to look at tcpdump. You are making the changes on both servers, right? – ewwhite Sep 4 '12 at 2:48 is subnet local and all multicast-capable interfaces will be (and must be) able to join. The other potential issue is rpf - if the source of the 230.x.x.x group is not local then there could potentially be problems if the unicast routes don't correspond. – rnxrx Sep 4 '12 at 7:02

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