Invalid MAC Address receiving at core switch and high CPU utilization

[Sihanu N]

Hi Experts,

We had a core switch in our environment and experiencing high cpu utilization during the office hours( around 80% and some times in above 90%). Also noticed that some invalid source address packet is receiving from some interfaces. But the cpu utilization

1) Is there any relation between the cpu utilization and the invalid sourceaddress packet?

2) Is this indicating an inside attack or a faulty interface in switches/NIC Card?

Please see the output of show logging

Log Buffer (4096 bytes):

ppressed 1 times)Packet received with invalid source MAC address (00:00:00:00:00

:00) on port Gi3/2 in vlan 1

1y1w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: Packet received with invalid sour

ce MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y1w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: Packet received with invalid sour

ce MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 129

1y1w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: Packet received with invalid sour

ce MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y2w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 2 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 129

1y2w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 1 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 129

1y2w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: Packet received with invalid sour

ce MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y2w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 3 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y2w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 2 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y2w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 1 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y2w: %SYS-6-CLOCKUPDATE: System clock has been updated from 07:32:33 UTC Mon Ja

n 30 2012 to 10:32:33 AST Mon Jan 30 2012, configured from console by CWLMS on v

ty1 (10.254.254.63).

1y2w: %SYS-5-CONFIG_I: Configured from console by CWLMS on vty1 (10.254.254.63)

1y2w: %SYS-6-CLOCKUPDATE: System clock has been updated from 10:33:01 AST Mon Ja

n 30 2012 to 18:59:00 AST Mon Jan 30 2012, configured from console by CWLMS on v

ty1 (10.254.254.63).

1y2w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 4 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y2w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: Packet received with invalid sour

ce MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y2w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 1 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y3w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 1 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y3w: %SYS-5-CONFIG_I: Configured from console by CWLMS on vty3 (10.254.254.78)

1y3w: %SYS-5-CONFIG_I: Configured from console by CWLMS on vty3 (10.254.254.78)

1y3w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: Packet received with invalid sour

ce MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y3w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 1 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y3w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: Packet received with invalid sour

ce MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y3w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: Packet received with invalid sour

ce MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 129

1y3w: %SYS-5-CONFIG_I: Configured from console by CWLMS on vty5 (10.254.254.76)

1y3w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: Packet received with invalid sour

ce MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y4w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 1 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y4w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 1 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y4w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: (Suppressed 1 times)Packet receiv

ed with invalid source MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

1y4w: %C4K_L2MAN-6-INVALIDSOURCEADDRESSPACKET: Packet received with invalid sour

ce MAC address (00:00:00:00:00:00) on port Gi3/2 in vlan 1

Kindly post your suggestions regarding this.

Advanced Thanks and Regards,

Sihanu N

[Thotsaphon Lueangwattanaphong · Accepted solution]

Hi,

    It's going to hit on CPU. You may check this link,https://supportforums.cisco.com/docs/DOC-4065

HTH,

Toshi

[Sihanu N]

Hi Toshi,

Many Many thanks for your support and information provided. I will check and revert after finding the source of the invalid MAC address broadcaster (NIC/switchport).

The second solution(switchport security) is not feasible in our environment as the port is connected to another Distribution switch (as the security shutdown will results in the network outage in that particular department)

Regards,

Sihanu N