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What does switchport block multicast do?
block multicast Enables unknown multicast flooding to the port.
What is Storm Control multicast?
Storm control enables the device to monitor traffic levels and to drop broadcast, multicast, and unknown unicast packets when a specified traffic level—called the storm control level or storm control bandwidth—is exceeded, thus preventing packets from proliferating and degrading the LAN.
What is block multicast?
Multicast traffic is network traffic that is addressed to a group of IP addresses instead of to a single address. If you want to block even more multicast traffic and reduce your risk of a denial of service (DoS) attack, you can choose to block multicast traffic from unknown addresses.
What is storm control in a switch?
When storm control is enabled on an interface, the switch monitors packets received on the interface and determines whether the packets are broadcast. The switch monitors the number of broadcast packets received within a one-second time interval.
Can a switchport block unicast / multicast-IP?
Considering above requirements, “ Unicast ” and “ Multicast ” traffic flooding can be stopped from some designated ports. Note – The flood blocking feature is supported on all switched ports (including PVLAN ports) and is applied to all VLANs on which the port is forwarding.
How does storm control work in a Cisco switch?
Storm control operates the same way across Cisco platforms; if the destination-mac-address is not in the CAM table, then then the switch must flood it out all ports in the Vlan (except the one it came in on). Suffient quantities of this kind of traffic would trigger your Unicast Storm Control thresholds.
Why is my switch flooded with unicast traffic?
Occasionally, unknown unicast or multicast traffic is flooded to a switch port because a MAC address has timed out or has not been learned by the switch. switchport block unicast and switchport block multicast commands to enable flood blocking on the switch.
Can a Cisco IOS switch affect unicast traffic?
The reality is (at least on IOS platforms) that unicast storm control affects all unicast traffic; the Cisco Nexus doc I quoted said it only affected traffic that was unknown unicast. I will endeavor to test on Nexus at a later date. Configure a Cisco IOS switch with unicast storm-control to throttle at 1Mbps.