On Wed, 2013-01-30 at 09:39 +0200, Jussi Peltola wrote:
High density virtual machine setups can have 100 VMs per host.
OK, I see where you are coming from now. Hm. If you have 100 VMs per host and 48 hosts on a switch, methinks you should probably invest in the finest switches money can buy, and they will have no problem tracking that state. While it is certainly a hefty dose *more*, it is geometrically, not exponentially more, so not a scalability issue IMHO. An ordinary old IPv4 switch tracks 4800 L2/port mappings in the scenario you describe. If each VM had just two addresses, it would be 9600... I wonder if there is hard information out there on how many multicast groups a modern switch can actually maintain in this regard. Are you saying you have seen actual failures due to this, or are you supposing? Serious question - is this a possible problem or an actual problem?
multicast groups - some virtual hosters give /64 per VM, which brings about all kinds of trouble not limited to multicast groups if the client decides to configure too many addresses to his server.
There is always some way to misconfigure a network to cause trouble. It's a bit unfair to make that IPv6's fault. As a matter of interest, what is the "all kinds of trouble" that a client can cause by configuring too many addresses on their server? Things that are not the client-side problems, obviously ;-) Regards, K. -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Karl Auer (kauer@biplane.com.au) http://www.biplane.com.au/kauer http://www.biplane.com.au/blog GPG fingerprint: B862 FB15 FE96 4961 BC62 1A40 6239 1208 9865 5F9A Old fingerprint: AE1D 4868 6420 AD9A A698 5251 1699 7B78 4EEE 6017