Cisco N5010P-N2K-BE, Руководство по настройке программного обеспечения

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S e n d f e e d b a c k t o n x 5 0 0 0 - d o c f e e d b a c k @ c i s c o . c o m
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Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
OL-16597-01
Chapter 31 Configuring QoS
Configuration Guidelines and Limitations
The system provides two predefined class maps for matching broadcast or multicast traffic. These class
maps are convenient for creating separate policy maps for unicast and multicast traffic. The predefined
class maps are as follows:
• class-all-flood
The class-all-flood class map matches all broadcast, multicast and unknown unicast traffic (across
all CoS values). If you configure a policy map with the class-all-flood class map, the system
automatically utilizes all available multicast queues for this traffic.
• class-ip-multicast
The class-ip-multicast class map matches all IP multicast traffic. Policy options configured in this
class map apply to traffic across all Ethernet CoS values. For example, if you enable optimized
multicast for this class, the IP multicast traffic for all CoS values is optimized.
If you configure this class as a no-drop class, the priority flow control capability is applied across
all Ethernet CoS values. In this configuration, pause will be applied to unicast and multicast traffic.
Note Only one of these predefined classes can be configured in the system QoS policy.
Policy for Fibre Channel Interfaces
The egress queues are not configurable for native Fibre Channel interfaces. Two queues are available as
follows:
• A strict priority queue to serve high-priority control traffic.
•
A queue to serve all data traffic and low-priority control traffic.
QoS for Traffic Directed to the CPU
The switch automatically applies QoS policies to traffic that is directed to the CPU to ensure that the
CPU is not flooded with packets. Control traffic, such as BPDU frames, is given higher priority to ensure
delivery.
Configuration Guidelines and Limitations
Switch resources (such as buffers, virtual output queues, and egress queues) are partitioned based on the
default and user-defined system classes. The switch software automatically adjusts the resource
allocation to accommodate the configured system classes.
To maintain optimal switch performance, follow these guidelines when configuring system classes and
policies:
• If less than four Ethernet classes are defined, up to two of these classes can be configured as no-drop
classes
. If more than three Ethernet classes are defined, only one of these classes can be configured
as a no-drop class. The default drop class is counted as an Ethernet class.
•
If priority flow control is enabled on an Ethernet interface, pause will never be applied to traffic with
a drop system class. PFC does not apply pause to drop classes and the link-level pause feature is
never enabled on an interface with PFC.