Digimer, Did you ever get a reply from anyone? If what you say is true, failure of one of our HSRP(HA) switches/routers might break the cluster. (if they don't share multicast menberships) I would guess that multicast groups originate in the cluster, not the switch. In that case, if the switch has been rebooted, the cluster needs to re-create the multicast groups on the switch. I would guess that the cluster itself needs to check if the switch is properly handling multicast. (subscribe to its own group and check if the packets are being handles correctly) This should provide an insight into clustering/multicast: http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note0918 6a008059a9df.shtml Regards, Kit -----Original Message----- From: linux-cluster-bounces@xxxxxxxxxx [mailto:linux-cluster-bounces@xxxxxxxxxx] On Behalf Of Digimer Sent: maandag 24 januari 2011 16:37 To: linux clustering Subject: A better understanding of multicast issues Hi all, It seems to me that a very good number of clustering problems end up being multicast and smart switch related. I know that IGMP snooping and STP are often the cause, and PIM can help solve it. Despite understanding this, though, I can't quite understand exactly *why* IGMP snooping and STP break things. Reading up on them leads me to think that they should cleanly create and handle multicast groups, but this obviously isn't the case. When a switch restarts, shouldn't it send a request to clients asking to resubscribe to multicast groups? When corosync starts, I expect it would also send multicast joins. Sorry if the question is a little vague or odd. I'm trying to get my head around the troubles when, on the surface, the docs seem to make the process of creating/managing multicast quite simple and straight forward. Thanks! -- Digimer E-Mail: digimer@xxxxxxxxxxx AN!Whitepapers: http://alteeve.com Node Assassin: http://nodeassassin.org -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
