Cisco IOS lets you change the EXP bits to a new value or implement the behavior of copying the EXP bits to the exposed IP precedence/DSCP bits on the egress LSR. In Cisco IOS, you can use the Modular QoS Command Line Interface (MQC) or Committed Access Rate (CAR) for this. However, MQC is the newest implemented feature and the one with the most capabilities, so it is the only one mentioned here.
You can use two commands in MQC to change the EXP bits of labels. The following command sets the EXP bits in the topmost label:
set mpls experimental topmost value
You can use it in an input or an output service policy.
The next command sets the EXP bits in the pushed label(s):
set mpls experimental imposition value