On Sun, Nov 17, 2002 at 06:03:37PM +0100, Michael Schwendt wrote: > On 17 Nov 2002 07:44:38 -0500, Doug Potter wrote:
> > Actually that is a class B address.
> >
> > The first octet of a class A is 1-126 (127 reserved for loop back)
> > class B is 128-191
> > class C is 192-223
> > since 172 is between the ranges of 128-191 that would make it class B
> > Class B subnet 255.255.0.0 or /16
> The step from Class B to /16 is beyond me. If memory serves
> correctly, the Class B subnet in RFC1918 is 172.16.0.0/12
> which would be netmask 255.240.0.0.
No no no... This is totally wrong.
RFC 1918 has nothing to do with the old and deprecated classful
address system. 172.16.0.0/12 is one of the ranges (that happens to
be in the old Class B address space) for private addresses.
I've heard enough erronious information in this thread at this
point and nobody has mentioned the fact that "Class A", "Class B",
"Class C", and "Class D" no longer exist for any intent and purposes.
The Internet now runs on CIDR. Classless Inter Domain Routing.
I've seen too many people arbitrarily refer to a /24 (CIDR notation)
at being a Class C. This is also WRONG. The old Class C addresses were a
/24 netmask (255.255.255.0 - 24 bits in the network field) and in the
address range of 192.0.0.0 through 223.255.255.255. An address of
172.16.10.0/24 is NOT a Class C nor was it ever. It meets the netmask
specification but is not in the Class C range.
It's in the Class B address space but, assuming that it's a
/24 netmask, it's not a Class B network either because it doesn't meet
the netmask specification. At most, it's a SUBNET of a Class B
network, under the old deprecated classful system. It also happens
to be a part of the private address space allocations, which is something
else, yet again.
Old Notation:
0.0.0.0 - 127.255.255.255 Class A range 255.0.0.0 netmask /8
128.0.0.0 - 191.255.255.255 Class B range 255.255.0.0 netmask /16
192.0.0.0 - 223.255.255.255 Class C range 255.255.255.0 netmaks /24
These are now, at best, default conditions for netmasks when the
netmask or CIDR bits are not specified. It would be better if we
simply DROPPED references to the old Classes entirely. I now refer
to my address space as being one of the "fossil Class B" addresses
(a Class B address allocated under the old Classful system and now
merely a /16 allocation).
To answer another message, the number in a / number (such as /12)
describe the number of network bits in the netmask. A netmask of 255.0.0.0
has 8 bits set so it's a /8. A netmask of 255.240.0.0 is a /12 because
it has 12 bits set (1111 1111 . 1111 0000 . 0000 0000. 0000 0000).
The original question asked was poorly phrased and has no real
deterministic answer. The "tightest" netmask, which totally encloses
all of those addresses in the original question, is a /24 which covers
the range from 172.16.0.0 - 172.16.0.255. It could also be contained
in a /23 netmask from 172.16.0.0 - 172.16.1.255 or a /22 netmask from
172.16.0.0 - 172.16.2.255, etc. The private address space, of which this
is a SMALL part, is specified by RFC to be 172.16.0.0 - 172.31.255.255
which is a /12 address space (encompassing 16 of the old Class B network
addresses) and which also encloses the entire address range listed
in the original message (plus a WHOLE lot more).
The best answer I could come up with is that it is PROBABLY
contained within a /24 address space (netmask 255.255.255.0) but may
be contained within a larger address space. The specific addresses
in question are in RFC allocated private address space and may not
be routed on the Internet (which wasn't asked but may be relevant).
Mike
--
Michael H. Warfield | (770) 985-6132 | [EMAIL PROTECTED]
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