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Configuring ITM and Top Traffic Using the CLI Integrated Traffic Monitoring

Any of the configured parameters can be changed at any time, once ITM is enabled; however, changing the

sample rate while enabled forces traffic flow entry expiration. Other configurations, such as disabling

traffic monitoring on an interface or changing expiration timers, will take place immediately but will not

force the expiration of any traffic flow entries.

Configuring Sampling

To employ sampling on an interface with ITM enabled, define the desired sample rate. By specifying a

certain number of packets out of a range of packets for collection, less traffic data is collected and stored

while still providing an accurate view of traffic activity. The following command is used to specify

sampling rates:

(config)#ip flow cache sample one-out-of <number> [random | deterministic]

For example, if you were configuring a sample rate of 1 packet out of every 200 for traffic monitoring on

any interface, the command would appear as follows:

(config)#ip flow cache sample one-out-of 200

Sampling can also be set to random or deterministic. Selecting random indicates that the one packet

collected from the packet flow will not be the same one every time. Selecting deterministic indicates that

the one packet collected from the packet flow will be the same one every time. By default, sampling is set

to random.

The command also supports a no parameter, which disables sampling. Sampling also has a range limit of 1

to 255 packets at a time.

Traffic Flow Entry Expiration

Traffic flow entries are the data collected about traffic flows. Entries are stored in flow cache and are

termed either active or inactive. Active traffic flows refer to single flows that continue to have packets

detected at the observation point; for example, with a long download. Active flows are forcibly expired in

30 minute intervals by default. Inactive traffic flows refer to idle flows which have no packets detected at

ip flow export template timeout-rate <minutes> Template information is re-sent to the export

destination every 30 minutes by default.

ip flow cache sample one-out-of <number>

[random | deterministic]

Sampling is disabled and every packet is

recorded. When enabled, sampling is set to

random.

ip flow cache timeout [active | inactive] Active is 30 minutes; inactive is 15 seconds.

For users of large routers (the NetVanta 5305 for example), sampling at a rate greater

than or equal to one out of every 100 packets is recommended.

Table 3. ITM Default Parameters

Command Default Value

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ADTRAN FNID Technical Information Seite 28