Cisco Cisco IOS XE 3.5E Guide De Dépannage
The configuration of QoS in the 3850 line has been improved due to its implementation of MQC (universal
QoS configuration model) configuration instead of the old MLS QoS (platform−dependent QoS
configuration) commands from the 3750 and 3560 lines of switches.
QoS configuration model) configuration instead of the old MLS QoS (platform−dependent QoS
configuration) commands from the 3750 and 3560 lines of switches.
The main differences are highlighted in this table:
Switch Type
3750
3850
Basic structure
MLS
MQC
QoS default
Disabled
Enabled
Global config
Support MLS QoS
Support some of MQC at ingress
Does not support MLS QoS
Support MQC [class−map, policy−map]
Interface config
Support MLS QoS config and some of MQC
CLI at ingress
CLI at ingress
Attach the policy to the interface
Port trust default
Disabled
Enabled
Port Ingress
Classification/Policing/Marking/
Queuing
Classification/Policing/marking
[NO Iingress Queuing !]
Port Egress
Queuing
Classification/Policing/marking/queuing
Switch Virtual
Interface (SVI)
Ingress
Interface (SVI)
Ingress
Classification/Policing/Marking
Classification/Marking
SVI Egress
None
Classification/Marking
It is important to recognize the main fundamental change in the QoS approach.
On the 3750, by default the QoS is disabled whereas on the 3850, it is enabled. Also in order to preserve
Layer 2 (L2)/Layer 3 (L3) QoS marking on the 3750 platform, a trust configuration must be applied.
Layer 2 (L2)/Layer 3 (L3) QoS marking on the 3750 platform, a trust configuration must be applied.
In the case of the 3850, all packets by default are trusted (the L2/L3 QoS marking is preserved), unless you
change it with an application of a specific policy map on the ingress or egress interface.
change it with an application of a specific policy map on the ingress or egress interface.
3750 QoS Model