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What is the default mapping of code points to Junos CoS forwarding classes?
The simplest way to classify a packet is to use behavior aggregate (BA) classification. The DSCP, DSCP IPv6, or IP precedence bits of the IP header convey the behavior aggregate class information. The information might also be found in the MPLS EXP bits, or IEEE 802.1p CoS bits.
By default, all incoming IPv4 packets are automatically assigned an implicit IP precedence classifier called ipprec-compatibility. The ipprec-compatibility IP precedence classifier maps IP precedence bits to forwarding classes and loss priorities, as shown in https://www.juniper.net/techpubs/en_US/junos15.1/topics/reference/general/default-ip-prec-compatibility-table-cos-config-guide.html.
The other default IP precedence classifier (called ipprec-default) overrides the ipprec-compatibility classifier when you explicitly associate it with a logical interface. The link https://www.juniper.net/techpubs/en_US/junos15.1/topics/reference/general/default-ip-prec-table-cos-config-guide.html, shows the forwarding class and PLP that are assigned to the IP precedence CoS bits when you apply the default IP precedence classifier.
Default DSCP and DSCP IPv6 classifiers: https://www.juniper.net/techpubs/en_US/junos15.1/topics/reference/general/default-dscp-table-cos-config-guide.html
Default MPLS EXP classifiers: https://www.juniper.net/techpubs/en_US/junos15.1/topics/reference/general/default-mpls-exp-table-cos-config-guide.html
Default IEEE802.1p classifiers: https://www.juniper.net/techpubs/en_US/junos15.1/topics/reference/general/default-802-1p-table-cos-config-guide.html
Default IEEE802.1ad classifiers: https://www.juniper.net/techpubs/en_US/junos15.1/topics/reference/general/default-802-1ad-table-cos-config-guide.html