Wednesday, September 26, 2012

IPv6 neighbor discovery on Nexus 7000

If you attach multiple devices directly to a Nexus 7000 switch and expect them to communicate with each other over IPv6 in the same VLAN, you really want to set no ip igmp snooping optimise-multicast-flood. Otherwise they can communicate with the L3 interface on the switch, but not with the others. All your attempts to do neighbor discovery fail, as this runs over multicast and non-IPv4 multicast is dropped due to this setting. Sadly it's on by default, so you need to apply this fix on any Nexus 7k where you want to do serious IPv6 switching on.

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