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Cisco MDS 9000 Family Fabric Manager Configuration Guide
OL-17256-03, Cisco MDS NX-OS Release 4.x
Chapter 60 Monitoring Network Traffic Using SPAN
Configuring SPAN
Configuring SPAN max-queued-packets
When a SPAN destination port is oversubscribed or has more source traffic than the speed of the
destination port, the source ports of the SPAN session will reduce in their throughput. The impact is
proportional to the amount of source traffic flowing in. Lowering the max-queued-packets value from
the default value of 15 to 1 prevents the impact on the source ports. It is necessary to reconsider the
default value for this setting as it may impact the source interface throughput.
By default, SPAN frames are dropped if the sum of the bandwidth of the source interfaces exceed the
bandwidth of the destination port. With a higher value, the SPAN traffic has a higher probability of
reaching the SPAN destination port instead of being dropped at the expense of data traffic throughput.
Note The span max-queued-packets can be changed only if no span sessions are currently active on the switch.
Note If you are spanning the traffic going through an FCIP interface, span copies may be dropped even if the
SD interface has more bandwidth than the amount of traffic being replicated. To avoid span drops, set
the max-queued-packets to a higher value; for example, 100.
Creating SPAN Sessions
To create SPAN sessions using Device Manager, follow these steps:
Step 1 Choose Interface > SPAN. You see the SPAN dialog box.
Step 2 Click the Sessions tab.
Step 3 Click Create.
You see the Create SPAN Sessions dialog box shown in Figure 60-5.
Figure 60-5 Create SPAN Sessions Dialog Box
Step 4 Choose the session ID (from 1-16) using the up or down arrows and click Create.
Step 5 Repeat Step 4 for each session you want to create.
Step 6 Enter the destination interface in the Dest Interface field for the appropriate session.
Step 7 Enter the filter VSAN list in the Filter VSAN List field for the appropriate session.
Step 8 Choose active or in active admin status in the Admin drop-down list.
Step 9 Click Apply to save your changes.
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