it audit checklist

By default, it audit checklist (in accordance with RFC 791 and RFC 2474) marks Interior Gateway Protocol (IGP) traffic (such as Routing Information Protocol [RIP and RIPv2], Open Shortest Path First [OSPF], and Enhanced Interior Gateway Routing Protocol [EIGRP]) to DSCP CS6. However, Cisco IOS Software also has an internal mechanism for granting priority to important control datagrams as they are processed through the router. This mechanism is called PAK_priority

As datagrams are processed though the router and down to the interfaces, they internally are encapsulated with a small packet header, referred to as the PAKTYPE structure. Within the fields of this internal header is a PAK_priority flag that indicates the relative importance of control packets to the router's internal processing systems. PAK_priority designation is a critical internal Cisco IOS Software operation and, as such, is not administratively configurable in any way