Default Rewrite Rule - Juniper JUNOS OS 10.3 - SOFTWARE Manual

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Default Rewrite Rule

Table 407: Default Packet Header Rewrite Mappings
Map from Forwarding Class
expedited-forwarding
expedited-forwarding
assured-forwarding
assured-forwarding
best-effort
3164
®
OS for EX Series Ethernet Switches, Release 10.3
NOTE: On Juniper Networks EX8200 Ethernet Switches, tagged Layer 3
interfaces and tagged RVIs do not automatically rewrite packets using the
default IEEE 802.1p rewrite rule. You must explicitly assign the IEEE 802.1p
rewrite rule to these interfaces for rewrites to occur.
Also, only one rewrite rule of each type can be assigned to any interface on
an EX8200 switch.
In effect, the rewrite rule performs the opposite function of the behavior aggregate (BA)
classifier used when the packet enters the switch. As the packet leaves the switch, the
final CoS action is generally the application of a rewrite rule.
You configure rewrite rules to alter CoS values in outgoing packets on the outbound
interfaces of an edge switch to meet the policies of a targeted peer. This allows the
downstream switch in a neighboring network to classify each packet into the appropriate
service group.
NOTE: When an IP precedence rewrite rule is active, bits 3, 4, and 5 of the
ToS byte are always reset to zero when code points are rewritten.
To enable a rewrite rule on an interface, you can either create your own rewrite rule and
enable it on the interface or enable a default rewrite rule. See "Defining CoS Rewrite
Rules (CLI Procedure)" on page 3216.
Table 407 on page 3164 shows the default rewrite-rule mappings. These are based on the
default bit definitions of Differentiated Services code point (DSCP), IEEE 802.1p, and IP
precedence values and the default forwarding classes.
When the CoS values of a packet match the forwarding-class and packet-loss-priority
(PLP) values, the switch rewrites markings on the packet based on the rewrite table.
PLP Value
low
high
low
high
low
Map to DSCP/IEEE 802.1p/IP Precedence
Value
ef
ef
af11
af12 (DSCP)
be
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