From: ron.wilkerson@gmail.com
Date: Mon Dec 22 2008 - 17:04:39 ARST
Right, but another way to say it would be:
A hex character is made up of only 4 bits, so breakdown the 01000010 into 2 parts.
(1st) 0100 - 4
(2nd) 0010 - 2
Then you have 42.
-----Original Message-----
From: Hobbs <deadheadblues@gmail.com>
Date: Mon, 22 Dec 2008 11:54:29
To: Atlanta CCIE<atlantaccie@gmail.com>
Cc: Cisco certification<ccielab@groupstudy.com>
Subject: Re: Question regarding CAR and IP Prec
Each bit in the mask corresponds to one of the prec/exp bits. Careful not to
confuse this with binary.
7=10000000
6=01000000
5=00100000
4=00010000
3=00001000
2=00000100
1=00000010
0=00000001
so to match 6 and 1 you would do: 01000010 which is 42 in hex.
On Mon, Dec 22, 2008 at 11:43 AM, Atlanta CCIE <atlantaccie@gmail.com>wrote:
> 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.
>
>
> Blogs and organic groups at http://www.ccie.net
>
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