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For CLI:
set ip-precedence-map <name> [ip-precedence-0|ip-precedence-1|ip-
precedence-2|ip-precedence-3|ip-precedence-4|ip-precedence-5|ip-
precedence-6|ip-precedence-7]
show ip-precedence-map
show ip-precedence-map <name>
Creating a Policy Map for L3 Priority Mapping
For ingress traffic on Trunk and Edge Ethernet (GE/10GE) ports, you can use a class map
to match the layer-3 priority value of incoming frames, and then use a policy map to assign a
corresponding P-bit (priority) value into the classified traffic.
This topic shows example outlines of single, specific DSCP value and multiple values used to
define mapping onto P-bits. This assumes that the upstream routers or aggregation switch
are not P-bit aware and do not manage traffic based on P-bit marking. Instead, DSCP is used
for this purpose.
For detailed instructions on how to create policy maps, see the following topics:
Creating a Class Map and Rules
(on page
90
)
Creating a Policy Map and Policies
(on page
93
)
Note:
The upstream traffic on a service VLAN must have the same priority value as is set
for downstream traffic.
For further information on layer-3 priority mapping, see:
Mapping Layer-3 Priority Values to P-Bits
The following table shows the different classes of traffic as they correlate to AF ranges.
Classes 1 to 4 are referred to as Assured Forwarding PHB (Per Hop Behavior). AF is divided
into four independently forwarded AF classes and is defined in RFC 2597. Within each AF
class there are three different levels of drop precedence. In case of network congestion, a
packet with a higher drop precedence (drop probability) value would be discarded first.
RFC 2597 recommends the following DSCP codepoints for the four AF classes.
Drop
Probability
Class 1
Class 2
Class 3
Class 4
Low
AF11
(DSCP 10)
AF21
(DSCP 18)
AF31
(DSCP 26)
AF41
(DSCP 34)
Medium
AF12
(DSCP 12)
AF22
(DSCP 20)
AF32
(DSCP 28)
AF42
(DSCP 36)
High
AF13
(DSCP 13)
AF23
(DSCP 22)
AF33
(DSCP 30)
AF43
(DSCP 38)
The AFxy, format uses x as the class number and y as the drop precedence.
