From: Atlanta CCIE (atlantaccie@gmail.com)
Date: Mon Dec 22 2008 - 16:43:22 ARST
Ok I thought I was ok with CAR but then I came across this example in DOCCD.
Usage Guidelines
Use this command to classify packets by the specified IP precedence, MAC
address, or MPLS experimental field values for a particular CAR access list.
You can then apply CAR policies, using the *rate-limit* command, to
individual rate-limit access lists. When packets in an access list are
classified in this manner, the packets with different IP precedences, MAC
addresses, or MPLS experimental field values are treated differently by the
CAR process.
You can specify only one command for each rate-limit access list. If you
enter this command multiple times using the same access list number, the new
command overwrites the previous command.
Use the *mask* keyword to assign multiple IP precedences or MPLS
experimental field values to the same rate-limit list. To ascertain the *
mask*value, perform the following steps.
*1. *Decide which precedences you want to assign to this rate-limit access
list.
*2. *Convert the precedences or MPLS experimental field values into 8-bit
numbers with each bit corresponding to one value. For example, an MPLS
experimental field value of 0 corresponds to 00000001; 1 corresponds to
00000010; 6 corresponds to 01000000; and 7 corresponds to 10000000.
*3. *Add the 8-bit numbers for the selected MPLS experimental field values.
For example, the mask for MPLS experimental field values 1 and 6 is
01000010.
*4. *The *access-list rate-limit* command expects hexadecimal format.
Convert the binary mask into the corresponding hexadecimal number. For
example, 01000010 becomes 42 and is used in the command. Any packets that
have an MPLS experimental field value of 1 or 6 will match this access list.
A mask of FF matches any precedence, and 00 does not match any precedence.
Can someone explain how they got a Mask of 42? I know its in HEX but I think
I am missing a point here.
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