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Community Member

** PLS HELP ** Multicast GDA Deletion after STP change occurs

Hello all :)

I have searched the bug toolkit to no avail, but I see a problem with a pair of 6500s.

Every time a port (any port) enters the STP transistion operation, all my mcast groups get deleted from the switch? I cant see a reason for why this would be normal operation? The port that enters STP state can be any port and does not even run multicast apps on them and is not in the "show multicast group" table.

Can anyone help as this "may" be causing us a GREAT deal of pain for our multicast apps?

Many thx from a troubled engineer :(

2003 Jan 28 17:02:39 GMT +00:00 %SPANTREE-6-PORTFWD: port 8/12 state in vlan 36 changed to forwarding.

2003 Jan 28 17:02:39 GMT +00:00 %MCAST-6-DELGDA:Deleting a GDA 01-00-5e-7f-00-01 in vlan 36

2003 Jan 28 17:02:39 GMT +00:00 %SNMP-5-TOPOTRAP:Topology Change Trap for Vlan [36]

2003 Jan 28 17:02:39 GMT +00:00 %MCAST-6-DELGDA:Deleting a GDA 01-00-5e-7f-00-02 in vlan 36

2003 Jan 28 17:02:40 GMT +00:00 %MCAST-6-DELGDA:Deleting a GDA 01-00-5e-7f-00-03 in vlan 36

2003 Jan 28 17:02:40 GMT +00:00 %MCAST-6-DELGDA:Deleting a GDA 01-00-5e-7f-00-04 in vlan 36

2003 Jan 28 17:02:40 GMT +00:00 %MCAST-6-DELGDA:Deleting a GDA 01-00-5e-7f-00-0a in vlan 36

4 REPLIES
Community Member

Re: ** PLS HELP ** Multicast GDA Deletion after STP change occur

I had this exact problem on our network but with a different series of switches. When a topology change occurs the multicast entries in the CAM table will be purged. Can you enable portfast on these ports to stop them from causing a topology change?

Community Member

Re: ** PLS HELP ** Multicast GDA Deletion after STP change occur

You might take a look at this doc... sounds like normal operation if I understand the document correctly.

http://www.cisco.com/en/US/tech/tk648/tk363/technologies_tech_note09186a00800ae957.shtml

Community Member

Re: ** PLS HELP ** Multicast GDA Deletion after STP change occur

That sounds like normal operation then. I assume the same goes for IGMP snooping as well as CGMP.

top stuff, many thx indeed :)

Community Member

Re: ** PLS HELP ** Multicast GDA Deletion after STP change occur

as the doc states, this is usual for CGMP but is it for an IGMP-only switch?

switchcat5500> sh igmp mode

IGMP Mode: auto

IGMP Operational Mode: igmp-only

IGMP Address Aliasing Mode: normal

I would have thought that an STP change for a port would not purge the WHOLE multicast table on a switch for a particular VLAN???

Is the stream interupted by this action, while the multicast table is rebuilt?

This looks very strange?

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