System information

Class of Service Configuration
3-101
Because different priority information may be contained in the traffic, this switch
maps priority values to the output queues in the following manner:
• The precedence for priority mapping is IP Precedence or DSCP Priority, and
then Default Port Priority.
• IP Precedence and DSCP Priority cannot both be enabled. Enabling one of
these priority types will automatically disable the other.
Selecting IP Precedence/DSCP Priority
The switch allows you to choose between using IP Precedence or DSCP priority.
Select one of the methods or disable this feature.
Command Attributes
•Disabled – Disables both priority services. (This is the default setting.)
• IP Precedence – Maps layer 3/4 priorities using IP Precedence.
• IP DSCP – Maps layer 3/4 priorities using Differentiated Services Code Point
Mapping.
Web – Click Priority, IP Precedence/DSCP Priority Status. Select Disabled,
IP Precedence or IP DSCP from the scroll-down menu.
CLI – The following example enables IP Precedence service on the switch.
Mapping IP Precedence
The Type of Service (ToS) octet in the IPv4 header includes three precedence bits
defining eight different priority levels ranging from highest priority for network control
packets to lowest priority for routine traffic. The default IP Precedence values are
mapped one-to-one to Class of Service values (i.e., Precedence value 0 maps to
CoS value 0, and so forth). Bits 6 and 7 are used for network control, and the other
bits for various application types. ToS bits are defined in the following table.
Console(config)#map ip precedence 4-150
Console(config)#
Priority Level Traffic Type Priority Level Traffic Type
7 Network Control 3 Flash
6 Internetwork Control 2 Immediate
5 Critical 1 Priority
4 Flash Override 0 Routine