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38-11
Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter 38 Configuring NetFlow
Configuring NetFlow Statistics Collection
Configuring a NetFlow Minimum Prefix Mask for Router-Based Aggregation
The minimum prefix mask specifies the shortest subnet mask that will be used for aggregating flows
within one of the IP-address based aggregation caches (e.g. source-prefix, destination-prefix, prefix). In
these caches, flows are aggregated based upon the IP address (source, destination, or both, respectively)
and masked by the longer of the Minimum Prefix mask and the subnet mask of the route to the
source/destination host of the flow (as found in the switch routing table).
Note The default value of the minimum mask is zero. The configurable range for the minimum mask is from
1 to 32. You should chose an appropriate value depending on the traffic. A higher value for the minimum
mask will provide more detailed network addresses, but it may also result in increased number of flows
in the aggregation cache.
To configure a minimum prefix mask for the Router-Based Aggregation feature, perform the tasks
described in the following sections. Each task is optional.
• Configuring the Minimum Mask of a Prefix Aggregation Scheme
• Configuring the Minimum Mask of a Destination-Prefix Aggregation Scheme
• Configuring the Minimum Mask of a Source-Prefix Aggregation Scheme
• Monitoring and Maintaining Minimum Masks for Aggregation Schemes
Configuring the Minimum Mask of a Prefix Aggregation Scheme
To configure the minimum mask of a prefix aggregation scheme, perform this task:
Configuring the Minimum Mask of a Destination-Prefix Aggregation Scheme
To configure the minimum mask of a destination-prefix aggregation scheme, perform this task:
Command Purpose
Step 1
Router(config)# ip flow-aggregation cache prefix
Configures the prefix aggregation cache.
Step 2
Router(config-flow-cache)# mask source minimum
value
Specifies the minimum value for the source
mask.
Step 3
Router(config-flow-cache)# mask destination minimum
value
Specifies minimum value for the
destination mask.
Command Purpose
Step 1
Router(config)# ip flow-aggregation cache destination-prefix
Configures the destination aggregation
cache.
Step 2
Router(config-flow-cache)# mask destination minimum
value
Specifies the minimum value for the
destination mask.