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The NDP protocol makes use of the solicited-node multicast address.

A host joins its own solicited-node multicast address group both localy (netsh int ipv6 show joins) and on the layer2 domain (a wireshark trace shows that a host configured with a new IPv6 address sends a MLD message for its solicited-node multicast address group).

Yet, a Cisco layer2 switch (S0) with IPv6 MLD snooping enabled, placed in between three hosts PC1,PC2,Server1 and an IPv6 PIMv2 router shows:

. no display of any solicited-node multicast groups recorded

. a recorded link-local multicast group (Multicast DNS, FF02::FB) proving link-local scopes multicast can be snooped

Doing some experiments shows that:

. IPv6 MLD snooping is functionning OK with regular IPv6 Multicast traffic, where the traffic is correctly switched relevant to the multicast joined clients (ie not-flooded)

. solicited-node multicast is not snooped, but flooded instead

So is IPv6 MLD snooping not performed by switches over solicited-node multicast address? Is it flooded by design ?

This is really puzzling / Thanks for any input :-)

networkIT
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  • See _[Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches](https://tools.ietf.org/html/rfc4541)_. – Ron Maupin May 07 '18 at 19:28

1 Answers1

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It seems your test is right. Please refer to: https://insinuator.net/2015/04/mld-yet-another-tale-on-complexity-in-ipv6/

There is one sentence included: A Cisco switch running IOS 15.4 configured to perform MLD-Snooping still leaves traffic related to ND untouched, it is broadcasted.

Twinkle Chu
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