[160001] in North American Network Operators' Group
Re: IPV6 in enterprise best practices/white papaers
daemon@ATHENA.MIT.EDU (Jussi Peltola)
Wed Jan 30 02:39:26 2013
Date: Wed, 30 Jan 2013 09:39:07 +0200
From: Jussi Peltola <pelzi@pelzi.net>
To: nanog@nanog.org
In-Reply-To: <1359528218.20278.57.camel@karl>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
High density virtual machine setups can have 100 VMs per host. Each VM
has at least a link-local address and a routable address. This is 200
groups per port, 9600 per 48 port switch. This is a rather large amount
of state for what it's worth. If you have mld snooping on a switch
aggregating multiple racks like this, you start hitting limits on some
platforms. There is a similar situation with a WLAN that has large
amounts of clients; a single AP, on the other hand, should not see that
many groups.
Multicast always requires state in the whole network for each group, or
flooding. In the case of ndp, flooding may very well be the better
option, especially if you view this as a DoS to your Really Important
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.
