[ClusterLabs] newbie question

[Sergei Gerasenko]

Thank you, Ken!

On Thu, May 11, 2017 at 11:19 AM, Ken Gaillot <kgaillot at redhat.com> wrote:

> On 05/05/2017 03:09 PM, Sergei Gerasenko wrote:
> > Hi,
> >
> > I have a very simple question.
> >
> > Pacemaker uses a dedicated "multicast" interface for the totem protocol.
> > I'm using pacemaker with LVS to provide HA load balancing. LVS uses
> > multicast interfaces to sync the status of TCP connections if a failover
> > occurs.
> >
> > I can understand services using the same interface if ports are used.
> > That way you can get a socket (ip + port). But there's no ports in this
> > case. So how can two services exchange messages without specifying
> > ports? I guess that's somehow related to multicast, but how exactly I
> > don't get.
> >
> > Can somebody point me to a primer on this topic?
> >
> > Thanks,
> >   S.
>
> Corosync is actually the cluster component that can use multicast, and
> it does use a specific port on a specific address. By default, it uses
> ports 5404 and 5405 when using multicast. See the corosync.conf(5) man
> page for mcastaddr and mcastport. Also see the transport option;
> corosync can be configured to use UDP unicast rather than multicast.
>
> I don't remember much about LVS, but I would guess it's the same -- it's
> probably just using a default port if not specified in the config.
>
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