Cisco N5K-M1600 - Expansion Module - 6 Ports Troubleshooting Manual page 61

Chapter 4 Troubleshooting QoS Issues
S e n d d o c u m e n t c o m m e n t s t o n e x u s 5 k - d o c f e e d b a c k @ c i s c o . c o m .
MTU for "class-default" value is 1500 when jumbo MTU configured
When the configuration for the network-qos policy-map sets the class-default to jumbo MTU, the show
queuing interface command indicates that the MTU for class-default is 1500.
Possible Cause
An incorrect startup configuration may exist after an upgrade.
Solution
If the switch has been upgraded to the 4.2(1)N1(1) release, make sure that you have used the write erase
command to delete the startup configuration. You can save the configuration first to another file name.
After the Nexus 5000 switch boots up with an empty configuration, reapply the original configuration.
You might lose your connectivity to the Nexus 5000 if you are using Telnet or SSH. It is recommended
that you use the console for this procedure.
Traffic not queued or prioritized correctly on Nexus 2148, Nexus 2232, and
Nexus 2248
After configuring all three types of policy maps (QoS, Network-QoS, and Queuing), the traffic is not
queued or prioritized correctly on Nexus 2148, Nexus 2232, and Nexus 2248 switches.
Possible Cause
The Nexus 2148, Nexus 2232, and Nexus 2248 FEX can only support CoS-based traffic classification.
The QoS service policy type configured under System QoS is populated from the Nexus 5000 to FEX
only when all the matching criteria are match cos. If other match clauses exist, such as match dscp or
match ip access-group in the QoS policy map, then the FEX does not accept the service policy. As a
result, all the traffic is placed into the default queue.
Use the show queuing interface command to ensure that the queues have been created properly.
Note
Solution
For the ingress traffic (from server to network) that is not marked with a CoS value, the traffic is placed
into the default queue on FEX. Once the traffic is received on the Nexus 5000, it is classified based on
a configured rule and are placed in the proper queue.
For the egress traffic (from Nexus 5000 to FEX, and then FEX to server), it is recommended that you
mark mark the traffic with a CoS value on the Nexus 5000 so that the FEX can classify and queue the
traffic properly.
The following example is a complete Nexus 5000 and Nexus 2232/Nexus 2248 configuration that
classifies the traffic and configures the proper bandwidth for each type of traffic. This example applies
only to the Nexus 5000 and Nexus 2248. The configuration for the Nexus 2148 is slightly different due
to the fact that Nexus 2148 has only two queues for user data. The Nexus 2232/Nexus 2248 has six
hardware queues for user data, which is the same as Nexus 5000.
Example:
//class-map for global qos policy-map, which will be used to create CoS-queue mapping.//
class-map type qos voice-global
match cos 5
class-map type qos critical-global
match cos 6
class-map type qos scavenger-global
OL-25300-01
Cisco Nexus 5000 Series Troubleshooting Guide
Improper Configurations
4-3