© Copyright IBM Corp. 2011 Chapter 7. Access Control Lists 89
VMap Example
In this example, EtherType 2 traffic from VLAN 3 server ports is mirrored to a
network monitor on port 4.
Using Storm Control Filters
The G8000 provides filters that can limit the number of the following packet types
transmitted by switch ports:
• Broadcast packets
• Multicast packets
• Unknown unicast packets (destination lookup failure)
Broadcast Storms
Excessive transmission of broadcast or multicast traffic can result in a broadcast
storm. A broadcast storm can overwhelm your network with constant broadcast or
multicast traffic, and degrade network performance. Common symptoms of a
broadcast storm are slow network response times and network operations timing
out.
Unicast packets whose destination MAC address is not in the Forwarding Database
are unknown unicasts. When an unknown unicast is encountered, the switch
handles it like a broadcast packet and floods it to all other ports in the VLAN
(broadcast domain). A high rate of unknown unicast traffic can have the same
negative effects as a broadcast storm.
Configuring Storm Control
Configure broadcast filters on each port that requires broadcast storm control. Set a
threshold that defines the total number of broadcast packets transmitted
(0-2097151), in Megabits per second. When the threshold is reached, no more
packets of the specified type are transmitted.
To filter broadcast packets on a port, use the following commands:
To filter multicast packets on a port, use the following commands:
To filter unknown unicast packets on a port, use the following commands:
RS G8000(config)# access-control vmap 21 packet-format ethernet
ethernet-type2
RS G8000(config)# access-control vmap 21 mirror port 4
RS G8000(config)# vlan 3
RS G8000(config-vlan)# vmap 21 serverports
RS G8000(config)# interface port 1
RS G8000(config-if)# broadcast-threshold <packet rate>
RS G8000(config-if)# multicast-threshold <packet rate>
RS G8000(config-if)# dest-lookup-threshold <packet rate>
RS G8000(config-if)# exit
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