Storm controll and unicast flooding
Question:
What is the difference between storm controll and unicast flooding? Also, why is unicast flooding called "unicast" if it refers to multicast as well? I know the second questions is picky but just wanted to hear opinoons on it.
Answer:
Storm control is a feature that can be used to independently control the level of broadcast, multicast or unicast traffic coming in on a particular port and take action based on the level of the traffic. Unicast flooding and storm control are not directly related features.
Unicast flooding does not refer to multicast flooding. When we talk aboiut unicast flooding in the context of transparent switching, we're really talking about "unknown unicast flooding" - the process on the switch that happens when it receives frame with the DA that it does not have an entry in its CAM table.
This example shows how to enable multicast traffic storm control on Gigabit Ethernet interface 3/16 and how to configure the traffic storm control level at 70.5 percent in Cisco WS-C3750X-24T-L :
Router# configure terminal
Router(config)# interface gigabitethernet 3/16
Router(config-if)# storm-control multicast level 70.5
Router(config-if)# end
This example shows how the traffic storm control level configured for one mode affects all other modes that are already configured on the Gigabit Ethernet interface 4/10:
Router# show run inter gig4/10
Building configuration...
Current configuration : 176 bytes
!
Router# interface GigabitEthernet4/10
Router# switchport
Router# switchport mode access
Router# storm-control broadcast level 70.00
Router# storm-control multicast level 70.00
Router# spanning-tree portfast edge
Router# end
Router# configure terminal
Router(config)# interface gigabitethernet 4/10
Router(config-if)# storm-control unicast level 20
Router(config-if)# end
Router# show interfaces gigabitethernet 4/10 counters storm-control
Port UcastSupp % McastSupp % BcastSupp % TotalSuppDiscards
Gi4/10 20.00 20.00 20.00 0
Router#