Figure 122. Statically and Dynamically Assigned dot1p for VLAN StackingWhen configuring Dynamic Mode CoS, you have two options:• Mark the S-Tag dot1p and queue the frame according to the original C-Tag dot1p. In this case, you must have other dot1p QoSconfigurations; this option is classic dot1p marking.• Mark the S-Tag dot1p and queue the frame according to the S-Tag dot1p. For example, if frames with C-Tag dot1p values 0, 6,and 7 are mapped to an S-Tag dot1p value 0, all such frames are sent to the queue associated with the S-Tag 802.1p value 0. Thisoption requires two different CAM entries, each in a different Layer 2 ACL FP block.NOTE: The ability to map incoming C-Tag dot1p to any S-Tag dot1p requires installing up to eight entries in the Layer 2QoS and Layer 2 ACL table for each configured customer VLAN. The scalability of this feature is limited by the impact ofthe 1:8 expansion in these content addressable memory (CAM) tables.Dell Networking OS Behavior: For Option A shown in the previous illustration, when there is a conflict between the queue selectedby Dynamic Mode CoS (vlan-stack dot1p-mapping) and a QoS configuration, the queue selected by Dynamic Mode CoS takesprecedence. However, rate policing for the queue is determined by QoS configuration. For example, the following access-portconfiguration maps all traffic to Queue 0:vlan-stack dot1p-mapping c-tag-dot1p 0-7 sp-tag-dot1p 1However, if the following QoS configuration also exists on the interface, traffic is queued to Queue 0 but is policed at 40Mbps (qos-policy-input for queue 3) because class-map "a" of Queue 3 also matches the traffic. This is an expected behavior.Examples of QoS Interface Configuration and Rate Policingpolicy-map-input in layer2service-queue 3 class-map a qos-policy 3!class-map match-any a layer2match mac access-group a!mac access-list standard aseq 5 permit any!qos-policy-input 3 layer2rate-police 40Likewise, in the following configuration, packets with dot1p priority 0–3 are marked as dot1p 7 in the outer tag and queued to Queue3. Rate policing is according to qos-policy-input 3. All other packets will have outer dot1p 0 and hence are queued to Queue 1.They are therefore policed according to qos-policy-input 1.policy-map-input in layer2service-queue 1 qos-policy 1service-queue 3 qos-policy 3!qos-policy-input 1 layer2rate-police 10!782 Service Provider Bridging
