Cisco N5K-C5010P-BF Troubleshooting Guide - Page 66

PFC, Link pause (flow control) not enabled on back to back Nexus 5000 switch links

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Chapter 4 Troubleshooting QoS Issues PFC Send document comments to [email protected]. switch# PFC Link pause (flow control) not enabled on back to back Nexus 5000 switch links When link pause (flow control) is not enabled on back-to-back Nexus 5000 switch links, packets are dropped while sending traffic on a no-drop class. Possible Cause If the peer Nexus 5000 switch supports PFC TLV with DCBX, then configuring flowcontrol send on and flowcontrol receive on will not enable the link pause. You have to disable the PFC TLV sent by DCBX on that interface. Use one of the following commands to verify: • Use the show interface ethx/y flowcontrol command and check to see if the operating state is off. • Use the show interface ethx/y priority-flow-control command and check to see if the operating state is on. Solution Configure the following commands under interface ethx/y to enable link pause instead of PFC on backto-back switch links. • no priority-flow-control mode on • flowcontrol receive on • flowcontrol send on Cannot enable "pause no-drop" on more than one ethernet class Cannot enable pause no-drop on more than one Ethernet class. CLI commands fail with the following error when trying to enable pause no-drop. ERROR: Module 1 returned status "Not enough buffer space available. Please change your configuration and re-apply" Possible Cause Nexus 5000 supports a maximum of three no drop classes (including FCoE). If five Ethernet classes are created, then there will be insufficient buffers to enable twoof the five Ethernet no-drop classes. You will get an error if not enough buffers exist to enable the no-drop. Example: class type network-qos s4 pause no-drop ERROR: Module 1 returned status "Not enough buffer space available. Please change your configuration and re-apply" Solution Cisco Nexus 5000 Series Troubleshooting Guide 4-8 OL-25300-01

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Send document comments to [email protected].
4-8
Cisco Nexus 5000 Series Troubleshooting Guide
OL-25300-01
Chapter 4
Troubleshooting QoS Issues
PFC
switch#
PFC
Link pause (flow control) not enabled on back to back Nexus 5000 switch links
When link pause (flow control) is not enabled on back-to-back Nexus 5000 switch links, packets are
dropped while sending traffic on a no-drop class.
Possible Cause
If the peer Nexus 5000 switch supports PFC TLV with DCBX, then configuring
flowcontrol send on
and
flowcontrol receive on
will not enable the link pause. You have to disable the PFC TLV sent by
DCBX on that interface.
Use one of the following commands to verify:
•
Use the
show interface ethx/y flowcontrol
command and check to see if the operating state is off.
•
Use the
show interface ethx/y priority-flow-control
command and check to see if the operating
state is on.
Solution
Configure the following commands under
interface ethx/y
to enable link pause instead of PFC on back-
to-back switch links.
•
no priority-flow-control mode on
•
flowcontrol receive on
•
flowcontrol send on
Cannot enable “pause no-drop” on more than one ethernet class
Cannot enable pause no-drop on more than one Ethernet class.
CLI commands fail with the following error when trying to enable pause no-drop.
ERROR:
Module 1 returned status "Not enough buffer space available. Please change your
configuration and re-apply"
Possible Cause
Nexus 5000 supports a maximum of three no drop classes (including FCoE). If five Ethernet classes are
created, then there will be insufficient buffers to enable twoof the five Ethernet no-drop classes.
You will get an error if not enough buffers exist to enable the no-drop.
Example:
class type network-qos s4
pause no-drop
ERROR:
Module 1 returned status "Not enough buffer space available. Please change your
configuration and re-apply"
Solution