MAC address flooding

What is MAC address flooding

MAC address flooding is an attack where the attacker sends frames to the switch with random source MAC addresses and flooding the MAC-address table in the switch. The CAM - Content Addressable Memory - gets full, and frames from valid hosts are flooded out of all ports.

Protecting against MAC Address flooding

Is done on a port basis.

Example

Up to five MAC address are allowed on user ports.

Port shutdown

If you want the port to go in err-disabled if more than five MAC-addresses are seen on the port

Switch(config)# interface range fastethernet 0/1 - 24
Switch(config-if)switchport port-security maximum 5
Switch(config-if)switchport port-security violation shutdown

Allow legal traffic and discard rest. No logging

If you want the port continue forwarding traffic from five MAC-addresses and discard remaining traffic and you don't want to log the attempt to use more than five MAC-addresses, use:

Switch(config)# interface range fastethernet 0/1 - 24
Switch(config-if)switchport port-security maximum 5
Switch(config-if)switchport port-security violation protect

Allow legal traffic and discard rest. SNMP trap logging

If you want the port continue forwarding traffic from five MAC-addresses and discard remaining traffic and you want to log the attempt to use more than five MAC-addresses. SNMP traps are sent, use:

Switch(config)# interface range fastethernet 0/1 - 24
Switch(config-if)switchport port-security maximum 5
Switch(config-if)switchport port-security violation restrict