From: Atlanta CCIE (atlantaccie@gmail.com)
Date: Mon Dec 22 2008 - 17:34:04 ARST
Thanks everyone for the quick input. I knew this but it was just not
clicking. As soon as I read these few explainations it all started to make
sense again. THanks again!
On Mon, Dec 22, 2008 at 2:04 PM, <ron.wilkerson@gmail.com> wrote:
> 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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>
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