Cisco Systems 3560 Manual De Usuario

After the hierarchical policy map is attached to an SVI, the interface-level policy map cannot 
be modified or removed from the hierarchical policy map. A new interface-level policy map 
also cannot be added to the hierarchical policy map. If you want these changes to occur, the 
hierarchical policy map must first be removed from the SVI. You also cannot add or remove a 
class map specified in the hierarchical policy map.

These are the policing guidelines:

The port ASIC device, which controls more than one physical port, supports 256 policers (255 
user-configurable policers plus 1 policer reserved for system internal use). The maximum number 
of user-configurable policers supported per port is 63. For example, you could configure 32 policers 
on a Gigabit Ethernet port and 8 policers on a Fast Ethernet port, or you could configure 64 policers 
on a Gigabit Ethernet port and 5 policers on a Fast Ethernet port. Policers are allocated on demand 
by the software and are constrained by the hardware and ASIC boundaries. You cannot reserve 
policers per port; there is no guarantee that a port will be assigned to any policer.

Only one policer is applied to a packet on an ingress port. Only the average rate and committed burst 
parameters are configurable.

You can create an aggregate policer that is shared by multiple traffic classes within the same 
nonhierarchical policy map. However, you cannot use the aggregate policer across different policy 
maps.

On a port configured for QoS, all traffic received through the port is classified, policed, and marked 
according to the policy map attached to the port. On a trunk port configured for QoS, traffic in all 
VLANs received through the port is classified, policed, and marked according to the policy map 
attached to the port. 

If you have EtherChannel ports configured on your switch, you must configure QoS classification, 
policing, mapping, and queueing on the individual physical ports that comprise the EtherChannel. 
You must decide whether the QoS configuration should match on all ports in the EtherChannel.

These are general QoS guidelines:

Control traffic (such as spanning-tree bridge protocol data units [BPDUs] and routing update 
packets) received by the switch are subject to all ingress QoS processing.

You are likely to lose data when you change queue settings; therefore, try to make changes when 
traffic is at a minimum.

A switch that is running the IP services image supports QoS DSCP and IP precedence matching in 
policy-based routing (PBR) route maps with these limitations:

You cannot apply QoS DSCP mutation maps and PBR route maps to the same interface.

You cannot configure DSCP transparency and PBR DSCP route maps on the same switch.