I thought with ip subnet zero
the no. of networks is 2^x-1
--- John Biel <[EMAIL PROTECTED]> wrote:
> IOS v11.3 to 12 requires the use of "ip subnet zero"
> command to allow 2^x
> instead of (2^x)-2.
> IOS v12 up enables this by default.
>
> So with IOS 12 its:
>
> Class A: 128 networks (minus loopback)
> Class B: 16384 networks
> Class C: 2,097,152 networks
>
> with default 11.3 it is as you show below, however
> you can set "ip subnet
> zero" to recover the use of them
> with IOS previous to 11.3 it is as you state below.
>
> (Taken from Exam Prep: Routing by Robert E. Larson
> et al p.31)
>
> "Ole Drews Jensen" <[EMAIL PROTECTED]> wrote in
> message
>
2019FB428FD3D311893700508B71EBFB48499F@RWR_MAIL_SVR">news:2019FB428FD3D311893700508B71EBFB48499F@RWR_MAIL_SVR...
> > Let me reconstruct my message.
> >
> > After having read through some more RFC's, I now
> believe that the
> following
> > is the truth. If you do not agree, please reply.
> >
> > CLASS A : 1.h.h.h - 126.h.h.h = 126 networks
> > CLASS B : 128.1.h.h - 191.254.h.h = 16382 networks
> > CLASS C : 192.0.1.h - 223.255.254.h = 2097150
> networks
> >
> > and
> >
> > CLASS A : n.0.0.1 - n.255.255.254 = 16777214 hosts
> > CLASS B : n.n.0.1 - n.n.255.254 = 65534 hosts
> > CLASS C : n.n.n.1 - n.n.n.254 = 254 hosts
> >
> > Thanks,
> >
> > Ole
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > Ole Drews Jensen
> > Systems Network Manager
> > CCNA, MCSE, MCP+I
> > RWR Enterprises, Inc.
> > [EMAIL PROTECTED]
> > http://www.oledrews.com/ccnp
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > NEED A JOB ???
> > http://www.oledrews.com/job
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> >
> >
> > -----Original Message-----
> > From: Ole Drews Jensen
> [mailto:[EMAIL PROTECTED]]
> > Sent: Monday, December 18, 2000 8:21 AM
> > To: '[EMAIL PROTECTED]'
> > Subject: IP addressses - Are networks 2^x or
> (2^x)-2 ???
> >
> >
> > I thought I knew it by heard now, but when I had
> to prove a point to
> > someone, I grapped some of my books, and they all
> have different
> > explanations. I therefore jumped to IETF's
> homepage and started surfing
> > their RFC's. BUT...
> >
> > On RFC 943 (Assigned Numbers) it says on page 1:
> >
> > Class A has 7 bit network number which allows 128
> (2^7) networks.
> > Class B has 14 bit network number which allows
> 16384 (2^14) networks
> > Class C has 21 bit network number which allows
> 2097152 (2^21) networks
> >
> > This looks right, because the MSB is 0 in a Class
> A, thus the 7 bits. It
> is
> > only 127 networks though, since 127.x.x.x is
> reserved. That is also
> > explained later in the RFC. The MSB in Class B is
> 10, thus the 14 bits.
> And
> > finally, the MSB in Class C is 110, thus the 21
> bits.
> >
> > On page page 10 however, it says that the maximum
> allowed networks are:
> >
> > Class A : (2^7 - 2) 126
> > Class B : (2^14 - 2) 16382
> > Class C : (2^21 - 2) 2097150
> >
> > It now looks like it follows the same rule as host
> calculations, where you
> > cannot use all 0's or all 1's.
> >
> > I have looked through all my books (I have a lot)
> and they all have
> slightly
> > different opinions about this.
> >
> > What is the right answer?
> >
> > Class A is from 0.x.x.x to 126.x.x.x OR 1.x.x.x to
> 126.x.x.x ?
> >
> > Class B is from 128.0.x.x to 191.255.x.x OR
> 128.1.x.x to 191.254.x.x ?
> >
> > Class C is from 192.0.0.x to 223.255.255.x OR
> 192.0.1.x to 223.255.254.x ?
> >
> > Regarding SUBNET's, they all have the same
> explanation, but here it is
> > anyway. If you use 192.168.1.0/28, you have 4 bits
> for the subnet and 4
> bits
> > for the hosts, which give you 2^4 - 2 = 14 subnets
> with 14 hosts each. I
> am
> > pretty sure that that is the right explanation.
> >
> > Thanks for any comments on this,
> >
> > Ole
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > Ole Drews Jensen
> > Systems Network Manager
> > CCNA, MCSE, MCP+I
> > RWR Enterprises, Inc.
> > [EMAIL PROTECTED]
> > http://www.oledrews.com/ccnp
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > NEED A JOB ???
> > http://www.oledrews.com/job
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> >
> > _________________________________
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>
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