Christine, Jan, Thank you for your responses. They helped me figure out what was happening in our clusters. We don't specify <cman cluster_id="n"> nor <cman><multicast addr="a.b.c.d"></cman> in cluster.conf. So it looks like cman is hashing the cluster name to get a cluster_id and multicast addr. -Steven Willis On 2014-05-12, at 03:44, Christine Caulfield <ccaulfie@xxxxxxxxxx> wrote: > On 09/05/14 21:03, Steven Willis wrote: >> If one doesn't pick a multicast address in the config file, how does corosync pick the address to use? I have three different clusters, none of them specify mcastaddr in corosync.conf and I see with tcpdump that they're all using different multicast addresses: >> >> 239.192.96.8 >> 239.192.173.163 >> 239.192.93.197 >> >> How does corosync come up with the 'default' multicast address? > > Corosync itself does not pick a multicast address, it needs to be told one. > > if you are running with cman (as I'm guessing you are looking at the > above) then it hashes the cluster name into a 16 bit number (called the > cluster ID) and uses that as the lower 16 bits of a multicast address > starting 239.192. > > cman_tool status will show all of these things and you can change them > in cluster.conf if needs be. > > <cman cluster_id="<n>"/> > > or > > <cman> > <multicast addr="xx.xx.xx.xx"/> > </cman> > > > Chrissie > _______________________________________________ > discuss mailing list > discuss@xxxxxxxxxxxx > http://lists.corosync.org/mailman/listinfo/discuss _______________________________________________ discuss mailing list discuss@xxxxxxxxxxxx http://lists.corosync.org/mailman/listinfo/discuss
