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56-11
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 56 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 is used for aggregating flows within
one of the IP-address based aggregation caches (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 provides 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, page 56-11
• Configuring the Minimum Mask of a Destination-Prefix Aggregation Scheme, page 56-11
• Configuring the Minimum Mask of a Source-Prefix Aggregation Scheme, page 56-12
• Monitoring and Maintaining Minimum Masks for Aggregation Schemes, page 56-12
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
Switch(config)# ip flow-aggregation cache prefix
Configures the prefix aggregation cache.
Step 2
Switch(config-flow-cache)# mask source minimum value
Specifies the minimum value for the source
mask.
Step 3
Switch(config-flow-cache)# mask destination minimum value
Specifies minimum value for the
destination mask.
Command Purpose
Step 1
Switch(config)# ip flow-aggregation cache destination-prefix
Configures the destination aggregation
cache.
Step 2
Switch(config-flow-cache)# mask destination minimum value
Specifies the minimum value for the
destination mask.