Cisco Bug: CSCuo39282 - N3K: QOS Classification Requires Set-QoS Group Cmd to Remark DSCP
Last Modified
Feb 19, 2018
Products (7)
- Cisco Nexus 3000 Series Switches
- Cisco Nexus 3064 Switch
- Cisco Nexus 3016 Switch
- Cisco Nexus 3064-T Switch
- Cisco Nexus 3048 Switch
- Cisco Nexus 3132Q Switch
- Cisco Nexus 3172 Switch
Known Affected Releases
6.0(2)U2(4)
Description (partial)
Symptom: This is day-one Nexus 3x00 QoS behavior (not a bug). A user-defined class-map cannot be configured with the "set qos-group 0" command. A qos-group has to be set when classifying traffic on DSCP value and rewriting it to another value. However, it should be noted that the traffic has to set to a qos-group that is not configured in the network-qos/ergress queuing policy to map it back to the default qos-group 0 when the classification policy matches specific DSCP values and preserves other DSCP values. In the following example, traffic matching DSCP 3 and 4 should be remarked to DSCP 0 and mapped to qos-group 0 (qos-group 7 is configured, but it isn't present in network-qos policy). Traffic matching DSCP 2 is mapped to qos-group 2 and all other traffic with DSCP values not previously matched are honored (not modified) and mapped to qos-group 0 using the "class-default" class-map. QoS Configuration: class-map type qos match-all RDMA match dscp 4 class-map type qos match-all SCAVENGER match dscp 8 class-map type qos match-all LOSSLESSTCP match dscp 3 policy-map type qos UPLINK_REMARKING class LOSSLESSTCP set dscp 0 set qos-group 7 class RDMA set qos-group 7 set dscp 0 class SCAVENGER set qos-group 2 QoS Verification: N3K-2# show policy-map type qos UPLINK_REMARKING Type qos policy-maps ==================== policy-map type qos UPLINK_REMARKING class type qos LOSSLESSTCP set dscp 0 set qos-group 7 class type qos RDMA set qos-group 7 set dscp 0 class type qos SCAVENGER set qos-group 2 class type qos class-default set qos-group 0 Conditions: This is only observed when classifying traffic using a DSCP value and setting it to another DSCP value. the "set qos-group" command has to be configured to rewrite the DSCP value.
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