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Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
OL_28731-01
Chapter 65 Configuring Flexible NetFlow
VSS Environment
22. Flow aging in flow cache is controlled through active and in-active timer configuration. The
minimum for active and in-active aging timers is 5 seconds. The timers must be in units of 5 seconds.
Note Flows in the hardware table are deleted after 5 seconds of in-activity irrespective of the active
or in-active timer configuration values. This allows you to create new hardware flows quickly.
23. First and Last-seen flow timestamp accuracy is within 3 seconds.
24. 2048 Flow monitors and records are supported.
When TTL is configured as a flow field, the following values are reported for a given packet TTL value.
Table 65-1 lists the packet TTL and reported values.
25. Cisco TrustSec (CTS) fields are supported. These fields use Netflow collector to monitor and
troubleshoot the CTS network, and to segregate traffic based on source group tag (SGT) values.
–
When configuring the source group tag (collect flow cts source group-tag), note the following:
The system copies the packets to software before it retrieves the CTS field. A large number of
flows mean that a large number of packets are copied to the software, possibly affecting CPU
performance.
The maximum number of (unique) hosts allowed in the switch (IP addresses) is 12,000.
In case of burst packets, the software may not be able to retrieve the CTS field because the
software queue is throttled.
–
When configuring the destination group tag (collect flow cts destination group-tag), note that
this CTS field value is collected only if you have already configured an IP-to-SGT mapping.
–
When configuring switch-derived source group tags (collect flow cts switch derived-sgt), note
that the switch derives this value locally.
• When packet length is configured as a flow field, the following values are reported for a given packet
length value. Table 65-2 lists the packet length and reported values.
Table 65-1 TTL Map: TTL Configured
Packet TT Value Reported Value
00
11
2-10 10
11-25 25
26-50 50
51-100 100
100-150 150
150-255 255
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