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Level 10
Level 10

Core issue

The default form of error message is:

%C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: Packet received with invalid source MAC address ([mac-addr] ) on port [char] in vlan [dec]

This means a packet was received with an all zero (00:00:00:00:00:00) or a multicast source address, for example, FF:FF:FF:FF:FF:FF. which is a Layer 2 broadcast. The packet is treated as invalid and no learning is done. Excessive flow of such packets can waste CPU cycles. This message is rate-limited and is displayed only for the first such packet received on any interface or VLAN. Subsequent messages display the cumulative count of all such packets received in given interval on all interfaces.


Check the switch configuration file in order to find the source of these packets on the specified port and take corrective action in order to fix them at the source end. For example, it can be due to a faulty NIC or connected hub. You can also setup a SPAN session to identify the source.

Alternatively,  you can also issue the switchport port-security limit rate invalid-source-mac command in order to enable port security on that interface in order to shutdown the port if the incoming rate of packets with invalid source mac address is too high.

Refer to these articles for more information:

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