ACX-5448/ACX-710 IRB to rewrite CoS is Not supported, causing traffic issue 

When you use IRB to rewrite CoS traffic, you may see unexpected traffic impact due to the undesired COS bit.

L3 rewrite (IP Prec /DSCP) on L2 is not supported on IRB interfaces for the ACX5448. 
If we use irb+L2, it hits the ACX5448 limitation, and there is no way to perform a DSCP 
rewrite on the IRB interface.

As a workaround you can use the following on the DUT:

set interfaces xe-0/0/1 flexible-vlan-tagging

set interfaces xe-0/0/1 native-vlan-id 4093

set interfaces xe-0/0/1 speed 1g

set interfaces xe-0/0/1 encapsulation flexible-ethernet-services

set interfaces xe-0/0/1 unit 315 description JTAC

set interfaces xe-0/0/1 unit 315 vlan-id 315

set interfaces xe-0/0/1 unit 315 family inet address 172.160.160.222/28

 

set routing-instances JTAC instance-type vrf

set routing-instances JTAC protocols ospf area 0.0.0.0 interface xe-0/0/1.315

set routing-instances JTAC interface xe-0/0/1.315

set routing-instances JTAC route-distinguisher 172.16.1.3:65501

set routing-instances JTAC vrf-target target:65501:1

set routing-instances JTAC vrf-table-label

 

set class-of-service interfaces xe-0/0/1 unit 315 rewrite-rules dscp dscp-rewrite

set class-of-service rewrite-rules dscp dscp-rewrite import default

set class-of-service rewrite-rules dscp dscp-rewrite forwarding-class best-effort loss-priority high code-point 000000

set class-of-service rewrite-rules dscp dscp-rewrite forwarding-class best-effort loss-priority low code-point 000000