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everyone

Having trouble with multicast on cisco WS-C4948-10GE (MPC8540).

I have two switches running:

System image file is "bootflash:cat4000-i5k91s-mz.122-25.EWA9.bin" and System image file is "bootflash:cat4500-entservicesk9-mz.122-46.SG.bin"

Both suffers from the same problem. I've configure several ports with vlan 100 which has multicast. Then it floods multicast to all ports which has vlan 100 what consumes 50Mb/s of link bandwith.

Swtich-2#show ip igmp snooping

Vlan 100:
--------
IGMP snooping                       : Enabled
IGMPv2 immediate leave              : Disabled
Explicit host tracking              : Enabled
Multicast router learning mode      : pim-dvmrp
CGMP interoperability mode          : IGMP_ONLY

Swtich-2#show mac address-table interface gigabitEthernet 1/7
Unicast Entries
 vlan   mac address     type        protocols               port
-------+---------------+--------+---------------------+--------------------
 100    64d1.5415.8a7b   dynamic ip                    GigabitEthernet1/7    

Multicast Entries
 vlan    mac address     type    ports
-------+---------------+-------+--------------------------------------------
100     ffff.ffff.ffff  system   Gi1/3,Gi1/7,Po1

Swtich-2#show ip igmp snooping mrouter 
Vlan    ports
----    -----
 100    Po1(dynamic)
Tomato
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1 Answers1

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The 4900 series doesn't support a snooping querier. So IGMP snooping will only work if there's IGMP to snoop on.

IGMP is used to dynamically register individual hosts in a multicast group on a particular LAN. Hosts identify group memberships by sending IGMP messages to their local multicast router. Under IGMP, routers listen to IGMP messages and periodically send out queries to discover which groups are active or inactive on a particular subnet. Cisco - IP Multicast Tech Overview

As this says, the local multicast router sends the IGMP queries. So there must be a local router on that VLAN that supports multicast and has PIM enabled. Otherwise, IGMP snooping will have nothing to snoop on.

David Schwartz
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  • Thanks for clarifying. There were plans to try another version of IOS. I will configure this according to your recommendations. – Tomato Dec 08 '18 at 12:23