IPV6 in enterprise best practices/white papaers

Karl Auer kauer at biplane.com.au
Wed Jan 30 10:24:20 UTC 2013

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 at biplane.com.au)

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