All things related to multicast

[Ray Soucy <>]

We noticed that a recent upgrade on our Catalyst 3560 and 3750s made
it so that MLD broke ND (and thus IPv6).  I haven't had time to check
into it more, but we assumed it was a bug and disabled MLD snooping
for now.  MLD snooping seemed to work OK in previous releases.

I did some searching a few weeks ago and couldn't find anyone else
talking about the problem.  This is the first time I've seen someone
else mention the issue.

Has anyone else seen MLD snooping break ND or is it just a
configuration oversight?

On Mon, Nov 8, 2010 at 2:27 AM, Multicast maillist
<>
 wrote:
> As per RFC 4541 (Considerations for Internet Group Management Protocol
> (IGMP)and Multicast Listener Discovery (MLD) Snooping Switches), it is
> inferred that forwarding criteria for all multicast IPv6 address (except
> ff02::1) is always based on group database as MLD is mandated for all the
> multicast v6 address.
>
> As per this, there is no special consideration for solicited multicast
> addresses or multicast addresses used for protocol control traffic.
>
> I feel this could cause issues in protocol adjacency maintenance or DAD
> process.
>
> Below is the link discussing about CISCO mld snooping breaking DAD
> functionality.
>
> http://networking.itags.org/networking-tech/148011/
>
> OSPFv3 adjacency could break if MLD snooping is enabled on a L2 switch
> between two OSPFv3 neighbors. (If the enable configuration happens just
> after a MLD query in the network, It would take another 120+ seconds to get
> the MLD report for FF02::5. OSPFv3 hello packets will not be forwarded by
> the MLD snooping enabled switch till report for FF02::5 is received and
> adjacency will break).
>
> There was a draft draft-pashby-magma-simplify-mld-snooping-01.txt stating
> that multicast traffic for solicited addresses and control packet reserved
> addresses should be forwarded to all ports. But that draft was not taken
> forward and has expired.
>
> What is the stand taken by vendors implementing MLD snooping to address the
> above issues?
>
> Shouldn’t the MLD snooping enabled switch forward the traffic for solicited
> multicast address and protocol control packets to all the ports of VLAN?
>
>
> Regards,
>
> Magna.



-- 
Ray Soucy

Epic Communications Specialist

Phone: +1 (207) 561-3526

Networkmaine, a Unit of the University of Maine System
http://www.networkmaine.net/