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igmp snooping

tedauction
Level 1
Level 1

Hello, I am running IGMP snooping.

When I run the command 'sh ip igmp snooping groups' I get the following populated result, however when I run the command 'sh mac address-table multicast' I get no result. I thought that if my IGMP groups table is getting populated, then the multicast mac address-table also would. Can anyone explain why not ?

i.e. from what I understood, the multicast mac address table should reflect the ports that comprise the multicast groups so if groups are showing up, how can the multicast mac address-table be empty ?

Thank you kindly.

sh ip igmp snooping groups (gives a result)


Vlan Group Type Version Port List
-----------------------------------------------------------------------
31 232.44.44.233 igmp v2 Gi0/5, Gi0/10
31 239.255.255.250 igmp v2 Gi0/5, Gi0/10
40 238.38.38.38 igmp v2 Gi0/1, Gi0/9
40 239.192.0.0 igmp v2 Gi0/1, Gi0/2,
Gi0/9
40 239.192.209.88 igmp v2 Gi0/2, Gi0/9
40 239.192.211.16 igmp v2 Gi0/1, Gi0/9
40 239.192.211.17 igmp v2 Gi0/1, Gi0/9
40 239.192.211.57 igmp v2 Gi0/1, Gi0/9
40 239.192.212.8 igmp v2 Gi0/1, Gi0/9

sh mac address-table multicast (shows no result)

Vlan Mac Address Type Ports
---- ----------- ---- -----

1 Reply 1

playerplease
Level 1
Level 1

Fortunately nowadays switches no longer forward multicast based on their destination MAC addresses , check the 32:1 IP Mac overlap to understand why . 

They instead use Layer 3 destination addresses .

Im however not sure why the multicast MAC address command is still there .. 

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