[Linux-cluster] multicast howto

[Patrick Caulfield]

Steven Dake wrote:
> On Tue, 2006-04-25 at 12:38 -0600, Wolfgang Pauli wrote:
>> Hi,
>>
>> I am trying to setup gfs on a cluster that spans over two subnets. dream is a 
>> node with to interefaces, one on each subnet. I thought the below setup 
>> should work (taken from http://gfs.wikidev.net/Installation ). But it does 
>> not. Can anybody tell me what is wrong with that?
>>
>> cheers,
>>
>> wolfgang
>>
>> <?xml version="1.0" ?>
>> <cluster config_version="2" name="alpha_cluster">
>> 	<fence_daemon post_fail_delay="0" post_join_delay="3"/>
>> 	<clusternodes>
>> 		<clusternode name="dream" votes="1">
>> 			<altname name"dream-e1">
>> 			<multicast addr="224.0.0.1" interface="eth0"/>
>> 			<multicast addr="224.0.0.9" interface="eth1"/>
>> 			<fence>
>> 				<method name="1">
>> 					<device name="human" nodename="dream"/>
>> 				</method>
>> 			</fence>
>> 		</clusternode>
>> 		<clusternode name="neo" votes="1">
>> 			<multicast addr="224.0.0.1" interface="eth0"/>
>> 			<fence>
>> 				<method name="1">
>> 					<device name="human" nodename="neo"/>
>> 				</method>
>> 			</fence>
>> 		</clusternode>
>> 		<clusternode name="node1" votes="1">
>> 			<multicast addr="224.0.0.9" interface="eth0"/>
>> 			<fence>
>> 				<method name="1">
>> 					<device name="human" nodename="node1"/>
>> 				</method>
>> 			</fence>
>> 		</clusternode>
>> 	</clusternodes>
>> 	<cman expected_votes="1" two_node="1">
>> 		<multicast addr="224.0.0.1"/>
>> 		<multicast addr="224.0.0.9"/>
>> 	</cman>
>> 	<fencedevices>
>> 		<fencedevice agent="fence_manual" name="human"/>
>> 	</fencedevices>
>> 	<rm>
>> 		<failoverdomains/>
>> 		<resources/>
>> 	</rm>
>> </cluster>
>>
> 
> Wolfgang
> Do not use the multicast address 224.0.0.1.  It is reserved for some
> various ipv4 operations.
> 
> Try using 225.0.0.9.  If you have a switch between the two subnets, I
> would expect RHCS to work.  If you have a router, I'd expect it not to
> work as the TTL must be set for multicast packets to hop across routers.
> For IPV6 the hop count must be set.  It appears you are using ipv4.
> 
> If you have a switch and it doesn't work, try turning off IGMP filtering
> in the switch +if it is a smart switch.  If it is a dumb switch it
> should just work with some additional latencies.

Good advice.

I've fixed the Wiki page, so it reflects reality a little more. I don't know
where that came from but it was confusing.


-- 

patrick