[c-nsp] Multicast flooding

[Blake Dunlap]

This is probably TCN based purging of snooping, and then it is being overly
cautious.

there is a good bit of tuning you can do related to this though

I'd start reading the documentation
http://www.cisco.com/en/US/docs/switches/metro/me3600x_3800x/software/release/12.2_52_ey/configuration/guide/swigmp.html#wp999774

-Blake


On Mon, Apr 8, 2013 at 5:50 PM, Jason Lixfeld <jason at lixfeld.ca> wrote:

> Quick question about multicast flooding/blocking...
>
> I know that by default a switch will forward multicast on all ports in the
> same broadcast domain.  I think I've got it disabled with switchport block
> multicast and igmp snooping enabled on the multicast vlan (4004) on the
> 15.0(2)SE1 3560G-24TS I have running here.  However, whenever I bounce a
> port configured with vlan 4004 on it (trunk or access), I get a period of
> 120 seconds where all ports in that VLAN are flooded with multicast traffic
> from Gi0/24.  After 120 seconds has elapsed, the multicast traffic from
> Gi0/24 dies off and the flooding to any other connected vlan 4004 ports
> subsides.
>
> There is an ME3600 connected to Gi0/24 and the multicast source is
> connected to an access port on that ME3600 in VLAN 4004.  The switchport
> block multicast is configured there as well.
>
> It seems like I'm missing, or, have misconfigured a knob somewhere, but
> I'm not quite sure what or where.
>
> Any insight?
>
> !
> interface range GigabitEthernet0/1 - 10
>  description Facing Client
>  switchport trunk encapsulation dot1q
>  switchport trunk native vlan 4082
>  switchport trunk allowed vlan 4004,4032,4082,4086
>  switchport mode trunk
>  switchport block multicast
>  switchport block unicast
>  spanning-tree portfast
> !
> interface GigabitEthernet0/24
>  description Facing Multicast Source
>  switchport access vlan 4004
>  switchport block multicast
>  switchport block unicast
> !
>
> Systems-Dev_Pit#sh ip igmp snooping vlan 4004
> Global IGMP Snooping configuration:
> -------------------------------------------
> IGMP snooping                : Enabled
> IGMPv3 snooping (minimal)    : Enabled
> Report suppression           : Enabled
> TCN solicit query            : Disabled
> TCN flood query count        : 2
> Robustness variable          : 2
> Last member query count      : 2
> Last member query interval   : 1000
>
> Vlan 4004:
> --------
> IGMP snooping                       : Enabled
> CAPWAP enabled                      : Disabled
> IGMPv2 immediate leave              : Disabled
> Multicast router learning mode      : pim-dvmrp
> CGMP interoperability mode          : IGMP_ONLY
> Robustness variable                 : 2
> Last member query count             : 2
> Last member query interval          : 1000
> Systems-Dev_Pit#
>
> Thanks in advance.
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