Administrator Guide
5. Queue the packet according to the DSCP marking. The DSCP to Queue mapping is as noted in Honoring dot1p Values on
Ingress Packets.
The behavior is similar for trust dot1p fallback in a Layer2 input policy map; the dot1p-to-queue mapping is noted in
Honoring dot1p Values on Ingress Packets.
To enable fall back to trust diserve or dot1p, use the following command.
• Classify packets according to their DSCP value as a secondary option in case no match occurs against the congured class
maps.
POLICY-MAP-IN mode
trust {diffserve | dot1p} fallback
Mapping dot1p Values to Service Queues
All trac is by default mapped to the same queue, Queue 0.
If you honor dot1p on ingress, you can create service classes based the queueing strategy in Honoring dot1p Values on Ingress
Packets. You may apply this queuing strategy globally by entering the following command from CONFIGURATION mode.
• All dot1p trac is mapped to Queue 0 unless you enable service-class dynamic dot1p on an interface or globally.
• Layer 2 or Layer 3 service policies supersede dot1p service classes.
• Create service classes.
INTERFACE mode
service-class dynamic dot1p
Guaranteeing Bandwidth to dot1p-Based Service Queues
To guarantee bandwidth to dot1p-based service queues, use the following command.
Apply this command in the same way as the bandwidth-percentage command in an output QoS policy (refer to Allocating
Bandwidth to Queue). The bandwidth-percentage command in QOS-POLICY-OUT mode supersedes the service-class
bandwidth-percentage command.
• Guarantee a minimum bandwidth to queues globally.
CONFIGURATION mode
service-class bandwidth-percentage
Applying an Input Policy Map to an Interface
To apply an input policy map to an interface, use the following command.
You can apply the same policy map to multiple interfaces, and you can modify a policy map after you apply it.
• You cannot apply an input Layer 2 QoS policy on an interface you also congure with the vlan-stack access command.
• If you apply a service policy that contains an ACL to more than one interface, the system uses ACL optimization to conserve
CAM space. The ACL optimization behavior detects when an ACL exists in the CAM rather than writing it to the CAM multiple
times.
• Apply an input policy map to an interface.
INTERFACE mode
service-policy input
Specify the keyword layer2 if the policy map you are applying a Layer 2 policy map; in this case, INTERFACE mode must be in
Switchport mode.
644
Quality of Service (QoS)