We're probably of the same opinion, but talking two different languages.
Would it be correct to say that:
CLASS A networks MSB in the first octet is 0, hence it has the following
range:
0.h.h.h - 127.h.h.h
After that has been said, we would go a step further and look at network
addresses in Class A that can be used.
We all know that 127.h.h.h is reserved for loopback, and the network address
cannot be all 0's, hence the addresses we're looking for has the following
range:
1.h.h.h - 126.h.h.h
If this is true, I must assume that the following goes with Classes B and C:
Class B range:
128.0.h.h - 191.255.h.h
Class B usable addresses:
128.1.h.h - 191.254.h.h
Class C range:
192.0.0.h - 223.255.255.h
Class C range:
192.0.1.h - 223.255.254.h
Am I correct in those statements? - If not, please explain.
Thanks,
Ole
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ole Drews Jensen
Systems Network Manager
CCNA, MCSE, MCP+I
RWR Enterprises, Inc.
[EMAIL PROTECTED]
http://www.oledrews.com/ccnp
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-----Original Message-----
From: Leigh Anne Chisholm [mailto:[EMAIL PROTECTED]]
Sent: Monday, December 18, 2000 1:18 PM
To: Ole Drews Jensen; Cisco@Groupstudy. Com
Subject: RE: IP addressses - Are networks 2^x or (2^x)-2 ???
I disagree. You've identified the VALID range of Class A, B, and C
addresses - addresses that can be assigned to end-systems. You have NOT
identified the FULL SCOPE of the Classes.
As per your previous email:
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
Class A addresses are those where the first octet value begins with 0.
Thus, all addresses in the range of 0.0.0.0 through 127.255.255.255 are
Class A addresses. Using the formula 2^n-2, you identify those addresses
within that range that can be used on end-systems. Using the formula 2^n-2,
you create the valid IP address range from within the Class A address range
of 1.0.0.0 through 126.255.255.255...
Class B addresses are those where the first octet value begins with the
combination "10". Class B addresses are in the range of 128.0.0.0 through
191.255.255.255. The VALID range of Class B IP addresses is determined by
the formula 2^n-2 when applying the Class B default subnet mask of
255.255.0.0.
Class C addresses are those where the first octet value begins with the
combination "110". Class C addresses are in the range of 192.0.0.0 through
223.255.255.255. The VALID range of Class C IP addresses is determined by
the formula 2^n-2 when applying the Class C default subnet mask of
255.255.255.0.
What John was pointing out, is that once you apply IP subnet zero, what
you've posted below as the VALID END-SYSTEM ASSIGNABLE range of IP addresses
changes (but the FULL SCOPE of the classes always remains the same).
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Ole Drews Jensen
Sent: December 18, 2000 9:59 AM
To: Ole Drews Jensen; '[EMAIL PROTECTED]'
Subject: RE: IP addressses - Are networks 2^x or (2^x)-2 ???
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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