Multicast Flood from a switch ip address???

A week or so ago, the following occured:

Out of the clear blue, we started experiencing network issues. Some of our main switches (4948TG) fiber ports went into err disable mode, WAN router was up and down, etc.

Wireshark captured IGMP coming from a switch (3750) ip address. This switch had nothing plugged into it at the time. Fiber was connected. We disconnected the switch from fiber and wireshark still captured the traffic. Rebooted the 6509E and it stopped. A few days later, we experienced the same from a different switch ip in another closet.

Here is a sample of the wireshark capture. It cames so fast that it just scrolled up the screen as fast as it could.

No.     Time        Source                Destination           Protocol Info
      1 0.000000            IGMP     V2 Membership Query / Join group

Frame 1: 60 bytes on wire (480 bits), 60 bytes captured (480 bits)
Ethernet II, Src: Cisco_d0:8e:c1 (00:18:ba:d0:8e:c1), Dst: IPv4mcast_00:00:23 (01:00:5e:00:00:23)
Internet Protocol, Src: (, Dst: (
Internet Group Management Protocol

Network in a nutshell: 6509E - Fiber Blades - 2 sup 720s-PIM Dense mode-Multicast routing
Closets - 3750's Fiber connected to 6509e
Multiple VLAN's configured., etc

Any ideas?
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Have you configured any special settings on main switche(4948TG) fiber ports. just show me the config for the switch...

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MrRudeAuthor Commented:
Nothing out of the ordinary on the 4948's. They aren't the core switches, the 6509 is. My main question is what would cause multicast from a switch ip? address aliasing?,etc.
Switch will not send any kind of is some host which is sending multicast and switch is forwarding it...
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MrRudeAuthor Commented:
Anyway to determine which host?
MrRudeAuthor Commented:
Lokking at the switch it states "ip multicast-routing distributed" is not configured - IP Mulicast packets will not be forwarded.
MrRudeAuthor Commented:
Not really what I was looking for, but at least shub answered.
is your issue resolved....?
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Network Management

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