[c-nsp] multicast on layer 2

[Andrew Fort]

Andrew K Ho wrote:
> Yes, I'm aware of the fact that every frame will be broadcast, but our 
> "planners" have "decided" it should be "that way."  I better stop there or 
> else everything I say will be in quotes :)  I'll pursue the PIM route but 
> as far as I was guessing, the server would have taken care of that, 
> otherwise, how would it work without a router interface or on a purely 
> layer 2 setup--i.e. using a hub only?
> 
> Thx again.
> 
> Andy

We had a variety of these problems on WS-SUP720, WS-X6816 and so on, 
including:

  - IGMP Snooping "not working" properly.  Customer moaned, we disabled, 
their PIM traffic worked.  We re-enabled, and PIM snooping did indeed 
show the PIM traffic.  Worked fine.  Then it randomly stopped working. 
Disable IGMP snooping (on their VLAN, or the whole switch).  Starts 
working.  Anyone know what commands to use to debug this further? 
(considering that you can't see the multicast destinations using 'show 
mac-').

  - After various network events, non-ARP'd IP/Multicast addresses (e.g. 
224.0.0.x such as the IP routing protocols that use multicast 
propogation) failed to work for customers in various VLANs.  Only way to 
recover these services was to remove the VLAN from all ports on the 
affected switch, remove the VLAN from the switch, and re-add.  Sounds 
like an ASIC programming problem, but again, very difficult to diagnose, 
as very difficult to reproduce in a lab environment. We still hit this 
one every now and then.

-andrew