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Re: [Linux-cluster] Choose between broadcast and multicast for cman



On Thu, 1 Jun 2006, Riaan van Niekerk wrote:

> Riaan van Niekerk wrote:
> > Is there any reason or advantage to use multicast over broadcast, which
> > offsets the complexity of multicast (relative to broadcast), e.g more
> > control, less traffic, others?
> 
> Generally multicast behaves the same as broadcast. The only time you would
> need multicast is if your nodes are on different subnets - in which case 
> you
> would also have to make sure the router had sufficiently low latencies to
> support clustering over it.
> 
> 
tnx Patrick


The RHCS 4 documentation does not give a recommendation for a multicast
address. cman man page and http://sources.redhat.com/cluster/doc/usage.txt
mention 224.0.0.1, which is a non-routable multicast address range, 
224.0.0.0/24 .

So if I understand this correctly:

Using this address or anything in the 224.0.0.0/24 range would give the
exact same effect as long as nodes are on the same subnet. If nodes are on
different subnets, a multicast address in another network should be used
(e.g. RHCS 3 defaults to 225.0.0.11).

Riaan



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