Cisco CAR 实现方法和机制

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Use the mask keyword to assign multiple IP precedence's to the same rate-limit list. To　　determine the mask value, perform the following steps:
　　Step 1 Decide which precedence's you want to assign to this rate-limit access list.
　　Step 2 Convert the precedence's into an 8-bit numbers with each bit corresponding to one
　　precedence. For example, an IP precedence of 0 corresponds to 00000001, 1 corresponds
　　to 00000010, 6 corresponds to 01000000, and 7 corresponds to 10000000.
　　Step 3 Add the 8-bit numbers for the selected precedence's together. For example, the
　　mask for precedence's 1 and 6 is 01000010.
　　Step 4 Convert the binary mark into the corresponding hexadecimal number. For
　　example, 01000010 becomes 0x42. This value is used in the access-list rate-limit
　　command. Any packets that have an IP precedence of 1 or 6 will match this access list. A
　　mask of FF matches any precedence, and 00 does not match any precedence.
　　In this example, a mask of 07 translates to 00000111, so IP precedence 0, 1, and 2 will be
　　policed.