Juniper IP SERVICES - CONFIGURATION GUIDE V 11.1.X, Configuration Manual

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Specifying an interval less than 10 sets a very high sampling rate that can severely
degrade performance. The lower the packet-sampling interval you configure, the
faster the sampling rate.
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For information about the effects of using the ip flow-sampling-mode
packet-interval command for the ES2 10G LM with either the ES2-S1 GE-8 IOA
or the ES2-S2 10GE PR IOA on E120 routers and E320 routers, see “Defining a
Sampling Interval” on page 100
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Example—Samples 1 out of 50 packets from the line module on which the
interface resides
host1(config)# ip flow-sampling-mode packet-interval 50
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Use the no version to return the sampling interval to its default value, 4 billion.
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See ip flow-sampling-mode packet-interval.
Setting Cache Size
Use the ip flow-cache entries command to limit the number of main flow cache
entries for the virtual router (as collected across all line modules that are running
J-Flow). After the cache size exceeds the flow-cache entry limit, the least recently
used flow is removed.
The possible flow-cache range is 1,024 – 524,288 entries. The default value is 65,536
entries.
ip flow-cache entries
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Use to limit J-Flow main flow cache entries.
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Example
host1(config)# ip flow-cache entries 80000
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Use the no version to return the cache size to its default value, 65535.
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See ip flow-cache entries.
Defining Aging Timers
After the virtual router creates a flow in the cache, the virtual router can remove the
flow at the expiration of either the active or the inactive timer.
Specifying the Activity Timer
Use the ip flow-cache timeout active command to specify a value for the activity
timer. The activity timer measures the amount of time that the virtual router has
been recording a datagram for a given flow. When this timer expires, the virtual
router exports the flow cache entry from the cache and removes the entry. This
process prevents active flows from remaining in the flow cache, and allows collected
data to appear in a timely manner. The possible range for the activity timer value is
1 – 60 minutes. The default value is 30 minutes.
Configuring Flow-Based Statistics Collection
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Chapter 3: Configuring J-Flow Statistics