can't see multicast mac-address (Server, Firewall) on a Cisco-Switch

[rnolden]

can't see multicast mac-address on a Cisco-Switch ! should i see the multicast mac-address from a node (Server, Firewall, etc.) which is connected to a Cisco-Switch L2 or L3-Port(29xx/35xx/45xx/65xx..)

Switch-default: IGMP + IGMP-Snooping enabled

no MCST-MAC's but CDP and STP uses MCST too !!!

known commands, and tested:

sh mac-address-table / IOS

sh cam dyn / CatOS

sh cam system /CatOS

regards,

Ralf

[Richard Burts · Accepted solution]

I am not sure what you are really looking for. And I am not sure how you are looking. But I assume that you are probably doing show cam dynamic (or show mac-address depending on switch model) and expecting to see multicast MAC addresses. Multicast MAC addresses do not show up in the cam (or mac-address table). The content of cam (or mac-address table) are learned by looking at incoming frames and noting the source MAC address. Since the source MAC is almost always a unicast address (the multicast MAC is the destination) you will not see the multicast MAC in the cam (or mac-address table).

If you are looking for multicast MACs on the switch you might try the show multicast group.

HTH

Rick

[Kevin Dorrell]

It depends which model you are using, but on my 2950, I get a good table from show mac-address-table multicast. You can even refine this to show mac-address-table multicast igmp-snooping. But this does not include the link-local multicasts like CDP and STP.

Kevin Dorrell

Luxembourg