Configuring Span Max-Queued-Packets; Configuring Span For Generation 2 Fabric Switches - Cisco AP776A - Nexus Converged Network Switch 5020 Configuration Manual
Cisco mds 9000 family cli configuration guide - release 4.x (ol-18084-01, february 2009)
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Chapter 51
Monitoring Network Traffic Using SPAN
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
Command
Step 3
switch(config-span)# source interface fc9/1 tx
switch(config-span)# source filter vsan 1-2
switch(config-span)# source interface fc7/1 rx
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.
To configure a span max-queued-packets for a SPAN session, follow these steps:
Command
Step 1
switch# config t
Step 2
switch(config)# span max-queued-packtes 1
switch(config-span)#
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.
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
Note
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.
Configuring SPAN for Generation 2 Fabric Switches
Cisco Generation 2 Fabric Switches (such as MDS 9124) support SPAN sessions in both directions, Rx
and Tx.
Note
While using Generation 2 Fabric Switches, you cannot create an additional active SPAN session when
you already have one.
The following example shows how to configure SPAN sessions for the ingress direction for this switch.
OL-18084-01, Cisco MDS NX-OS Release 4.x
Purpose
Configures the source fc9/1 interface in the
egress (Tx) direction.
Configures VSANs 1 and 2 as session filters.
Configures the source fc7/1 interface in the
ingress (Rx) direction.
Purpose
Enters configuration mode.
Configures the SPAN max-queued-packets.
Cisco MDS 9000 Family CLI Configuration Guide
Configuring SPAN
51-9
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