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IGMP Snooping Port List

Hi all,


As output below, hosts that want to subscribe multicast from a publisher and are not able to for a particular group, all  the other groups in subnet 239.181.4.x work apart from, why is Po400 not included in the Port list as below? All hosts sit on the same vlan and on the same switch which is a Layer 2 switch attached to switch SW2-VDC10.


Po400 is a special Po that sends multicast across buildings so that multicast doesn't traverse our OTV network for these streams to work. Po31 is a Po that connects to L2 switch

SW2-VDC10# show ip igmp snooping groups | i 239.181.4.
901 v2 D Po31 Po400
901 v2 D Po400 Po31
901 v2 D Po400 Po31
901 v2 D Po400 Po31
901 v2 D Po31
901 v2 D Po400
901 v2 D Po400 Po31
901 v2 D Po400 Po31
901 v2 D Po400 Po31



show ip igmp snooping vlan 901
IGMP Snooping information for vlan 901
IGMP snooping enabled
Lookup mode: IP
Optimised Multicast Flood (OMF) enabled
IGMP querier present, address: 10.x.x.3, version: 2, i/f Po400
Switch-querier disabled
IGMPv3 Explicit tracking enabled
IGMPv2 Fast leave disabled
IGMPv1/v2 Report suppression enabled
IGMPv3 Report suppression disabled
Link Local Groups suppression enabled
Router port detection using PIM Hellos, IGMP Queries
Number of router-ports: 2
Number of groups: 205
VLAN vPC function disabled
Active ports:
Po31 Po400


sh ip igmp groups
IGMP Connected Group Membership for VRF "default" - matching Group ""
Type: S - Static, D - Dynamic, L - Local, T - SSM Translated
Group Address Type Interface Uptime Expires Last Reporter D Vlan901 21:03:17 00:03:32 10.x.x.24

Cisco Employee



Usually that means we didn't get a membership report on that interface asking for that multicast group. Are we sure membership reports are making it across Po400 to this switch? A packet capture would confirm. 


Without seeing configs it would be difficult to say if you maybe have a filter in place or something. However, if the rest of the multicast works in the vlan, you would think this group would as well. Is the source of over Po31 or Po400?


Hope that helps!

-Bradley Selzer
CCIE# 60833

Hi Bradley,


Po31 is the port channel to another VDC which controls all other traffic excluding vlan901


Po400 is the port channel in our Multicast VDC so any multicast for vlan 901 will not route across OTV as above.


Multicast VDC there is a Prefix List:


ip pim auto-rp listen forward
ip pim use-shared-tree-only group-list prefix-list SHARED-TREE-LIST
vlan 901

ip prefix-list SHARED-TREE-LIST

ip prefix-list SHARED-TREE-LIST description multicast groups which are forced to use the shared tree

seq 5 permit





Is the source of local to the switch or is it over Po400? Is there a client over Po400 that is requesting that group? It seems you are not getting an IGMP membership report from a client over Po400. 


That PIM config looks fine. All groups in the should behave the same. 


Hope that helps!

-Bradley Selzer
CCIE# 60833

Host is on a separate L2 switch. Host ports configured for L2 Vlan901


L2 switch (9300) trunks to Distribution Switch VDC2 (7710) on a different Port channel Po203 on this Switch 7710 we have configured another VDC for Multicast where Po400 is configured and also where the Layer 3 Interface Vlan 901 is configured.


Hope this explains things.


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