<div dir="ltr"><div class="gmail_default" style="font-size:small">Thank you, Ken!</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, May 11, 2017 at 11:19 AM, Ken Gaillot <span dir="ltr"><<a href="mailto:kgaillot@redhat.com" target="_blank">kgaillot@redhat.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On 05/05/2017 03:09 PM, Sergei Gerasenko wrote:<br>
> Hi,<br>
><br>
> I have a very simple question.<br>
><br>
> Pacemaker uses a dedicated "multicast" interface for the totem protocol.<br>
> I'm using pacemaker with LVS to provide HA load balancing. LVS uses<br>
> multicast interfaces to sync the status of TCP connections if a failover<br>
> occurs.<br>
><br>
> I can understand services using the same interface if ports are used.<br>
> That way you can get a socket (ip + port). But there's no ports in this<br>
> case. So how can two services exchange messages without specifying<br>
> ports? I guess that's somehow related to multicast, but how exactly I<br>
> don't get.<br>
><br>
> Can somebody point me to a primer on this topic?<br>
><br>
> Thanks,<br>
> S.<br>
<br>
Corosync is actually the cluster component that can use multicast, and<br>
it does use a specific port on a specific address. By default, it uses<br>
ports 5404 and 5405 when using multicast. See the corosync.conf(5) man<br>
page for mcastaddr and mcastport. Also see the transport option;<br>
corosync can be configured to use UDP unicast rather than multicast.<br>
<br>
I don't remember much about LVS, but I would guess it's the same -- it's<br>
probably just using a default port if not specified in the config.<br>
<br>
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</blockquote></div><br></div>