Re: Class "A" prefix-list

*

Class A networks that are NOT subnetted:

R2(config)#ip prefix-list Class-A seq 5 permit 0.0.0.0/1 ge 8 le 8

Class A networks are identified as follows:

Where n identifies the network bits and h identifies the host bits.

0nnnnnnn hhhhhhhh hhhhhhhh hhhhhhhh

7 First bit is set to 0; Therefore there are
7 network bits; 24 host bits

7 First octet: 0 - 127

7 126 Class As exist (0 and 127 are
reserved)

7 16,777,214 hosts on each Class A

Note the most significant bit of the first octet is set to a binary 0, the
rest of the bits in the first octet can be zeros or ones, therefore, if the
most significant bit of the first octet is 0 it must be class A. The
prefix-list picks on the first bit by using a /1 prefix-length.

Class A networks that are or are not subnetted:

R2(config)#ip prefix-list Class-A seq 5 permit 0.0.0.0/1 ge 8 le 32

Note in this case the prefix-list picks on class A, with a prefix-length of
greater than or equal 8 and less than or equal 32, which means that all
major class A networks, plus all class A networks that are subnetted.

*On Wed, Jun 1, 2011 at 1:45 PM, Hammer cisco <cisco.iers_at_gmail.com> wrote:

> thanks danel ,
>
> but still i need to know exactly what's the difference between 0.0.0.0/1ge
> 8 and 0.0.0.0/1 le 32
>
> as i think all class A networks starting from mask 8 and greater , i have
> not seen a network with mask less 8
>
> On 1 June 2011 23:35, Daniel Kutchin <daniel_at_kutchin.com> wrote:
>
> > If you just want to match Class A's with 8 bit masks, Class B's with 16
> bit
> > masks, and class C's with 24 bit masks.
> >
> > 0.0.0.0/1 ge 8 le 8
> > 128.0.0.0/2 ge 16 le 16
> > 192.0.0.0/3 ge 24 le 24
> >
> > If you want to match anything in the individual address spaces for class
> > A,B, C
> > 0.0.0.0/1 le 32
> > 128.0.0.0/2 le 32
> > 192.0.0.0/3 le 32
> >
> >
> > Class A- binary first bit 0.
> > Class B - binary first two bits 10.
> > Class C - binary first three bits 110.
> >
> > -
> > Daniel
> >
> >
> > -----Original Message-----
> > From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> > Hammer cisco
> > Sent: Mittwoch, 1. Juni 2011 21:38
> > To: ccielab_at_groupstudy.com
> > Subject: Class "A" prefix-list
> >
> > Hi experts,
> >
> > i am a little bit confused about the exact prefix-list we can use to
> match
> > all class A network address routes :
> >
> > ip prefix-list 0.0.0.0/1 ge 8
> >
> > or
> >
> > ip prefix-list 0.0.0.0/1 le 32
> >
> >
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> >
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--
*Narbik Kocharians
*CCSI#30832, CCIE# 12410 (R&S, SP, Security)
www.MicronicsTraining.com <http://www.micronicstraining.com/>
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