Cisco N5K-M1600 - Expansion Module - 6 Ports Troubleshooting Manual page 67

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 .
If you create five ethernet classes, then there will be an insufficient number of buffers to configure two
of the five Ethernet no-drop classes. If you delete two Ethernet classes and configure the remaining three
Ethernet classes (including class-default), then no-drop can be enabled on two of the Ethernet classes.
Changing no-drop configuration causes VPC peer-link to go down and FEX to go
offline
Changing the QoS no-drop configuration causes the VPC MCT peer-link to go down and FEX to go
offline.
Possible Cause
The network QoS policy parameters, such as MTU and pause, are treated as type1 parameters and should
match between the VPC primary and secondary nodes. If a mismatch exists between the VPC primary
and secondary nodes, then the VPC peer-link does not come up and FEX goes offline. Only CoS based
class no-drop/MTU parameters are considered as type 1 consistency checked for VPC. If you configure
an ACL based class, then it is not treated as a vtype 1 parameter for VPC.
Use one of the following commands to verify:
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•
Solution
Configure the similar no-drop class configuration between the VPC primary and secondary nodes. Any
mismatch of no-drop policy on nqos CoS-based class parameters causes a type1 inconsistency.
Pause enabled on all cos values when no-drop enabled on class-ip-multicast
Priority flow control enables pause on all CoS values when no-drop is enabled on the class-ip-multicast
class.
Possible Cause
When you create a class-ip-multicast class and no-drop is enabled, then pause is enabled on all of the
CoS values.
Use the show interface ethx/y priority-flow-control command and check that the VL bitmap is enabled
for all CoS values (ff).
Solution
Use the following commands to enable PFC on CoS 4 only, instead of on all CoS values under the
class-ip-multicast class.
•
•
•
OL-25300-01
show vpc brief
show vpc consistency-parameters global
Policy-map type network-qos system
Class type network-qos class-ip-multicast
Pause no-drop pfc-cos 4
Cisco Nexus 5000 Series Troubleshooting Guide
PFC
4-9