Packet Rewriting on Services Interfaces
On M Series routers, you can configure rewrite rules to change packet header information and attach it to an output interface. Because these rules can possibly overwrite the DSCP marking configured on Multiservices and Services PICs, it is important to create system-wide configurations carefully.
For example, knowing that the Services or Multiservices PICs can mark packets with any ToS or DSCP value and the output interface is restricted to only eight DSCP values, rewrite rules on the output interface condense the mapping from 64 to 8 values with overall loss of granularity. In this case, you have the following options:
Remove rewrite rules in the output interface.
Configure the output interface to include the most important mappings.