Cisco Nexus 9000 Series Configuration Manual page 71

Configuring Classification
• QoS classification is not supported on the FEX interfaces ingressing the VXLAN traffic. This limitation
is applicable to all Cisco Nexus 9000 Series switches.
• For matching the packets based on DSCP, CoS, or precedence in Cisco Nexus 9300-EX platform switches,
the TCAM entries for both IPv4 (single-wide is 1 entry) and IPv6 (double-wide are 2 entries) are installed
in the hardware. For example, if you match DSCP 4, 3 entries are installed in the hardware, 1 entry for
IPv4 and 2 entries for IPv6.
• You can specify a maximum of 1024 match criteria in a class map.
• You can configure a maximum of 128 classes for use in a single policy map.
• When you match on an ACL, the only other match you can specify is the Layer 3 packet length in a
match-all class.
• The match-all option in the class-map type qos match-all command is not supported. The match criteria
of this command becomes the same as in the class-map type qos match-any command. The class-map
type qos match-all command yields the same results as the class-map type qos match-any command.
• You can classify traffic on Layer 2 ports based on either the port policy or VLAN policy of the incoming
packet but not both. If both are present, the device acts on the port policy and ignores the VLAN policy.
• When a Cisco Nexus Fabric Extender (FEX) is connected and in use, data traffic should not be marked
with a CoS value of 7. CoS 7 is reserved for control traffic transiting the Fabric Extender.
• Control traffic (control frames) from the switch to the FEX are marked with a CoS value of 7 and are
limited to a jumbo MTU frame size of 2344 bytes.
• FEX host interfaces (HIF) are supported by the FEX QoS policy.
• A jumbo ping (MTU of 2400 or greater) from a switch supervisor with a COS of 7 to a FEX host fails
because the control queue on a FEX supports an MTU limited to 2240.
• QoS classification policies are not supported under system qos for Layer 2 switch ports. However, you
can configure a QoS policy to classify the incoming traffic based on CoS/DSCP and map it to different
queues. The QoS policy needs to be applied under all the interfaces that require the classification.
• A QoS policy with a MAC-based ACL as a match in the class map does not work for IPv6 traffic. For
QoS, IPv6 traffic needs to be matched based on IPv6 addresses and not on MAC addresses. (7.0(3)F3(3)
and later 7.0(3)F3(x) releases)
• As a best practice, avoid having a voice VLAN configuration where an access VLAN is same as the
voice VLAN.
The following are alternative approaches:
• Cisco Nexus 9230QC, 9272Q, 9232C, 9236C, and 92300YC switches; and Cisco Nexus 9160YC-X
switches.
• QoS TCAM carving is supported on ALE (Application Leaf Engine) enabled switches.
• Only system level policies are supported.
• Match on CoS is supported.
• Match on QoS-group is supported.
Cisco Nexus 9000 Series NX-OS Quality of Service Configuration Guide, Release 7.x
Guidelines and Limitations
57