chan@dciem.dciem.dnd.ca (Kam Tim CHAN) (10/20/89)
I am in the process of setting up a new subnetting environment, and
I noted the following comment :
In RFC950 (Internet Standard Subnetting Procedure) :
: Special Addresses:
:
: From the Assigned Numbers memo [9]:
:
: "In certain contexts, it is useful to have fixed addresses
: with functional significance rather than as identifiers of
: specific hosts. When such usage is called for, the address
: zero is to be interpreted as meaning "this", as in "this
: network". The address of all ones are to be interpreted as
: meaning "all", as in "all hosts". For example, the address
: 128.9.255.255 could be interpreted as meaning all hosts on
: the network 128.9. Or, the address 0.0.0.37 could be
: interpreted as meaning host 37 on this network."
:
: It is useful to preserve and extend the interpretation of these
: special addresses in subnetted networks. This means the values
: of all zeros and all ones in the subnet field should not be
: assigned to actual (physical) subnets.
However, I was thinking of using just 1 bit to be the subnet field,
therefore my subnet field is either all zero or all one. Would any one of
you comment on this special case issue, please ?
Thanks in advance.
Tim Chan
--
Tim Chan, Systems Specialist (416)-635-2073
Defence and Civil Institute of Environmental Medicine
UUCP: uunet!mnetor!dciem!chan or {decvax|ihnp4|watmath}!utzoo!dciem!chan
Internet: chan@dretor.dciem.dnd.ca or chan%dretor@zorac.dciem.dnd.cacarlson@uxh.cso.uiuc.edu (10/22/89)
(This is a perfect example of quoting ASCII documents;
I couldn't do this with a PostScript file!)
RFC1122 INTERNET LAYER October 1989
IP addresses are not permitted to have the value 0 or -1 for
any of the <Host-number>, <Network-number>, or <Subnet-
number> fields (except in the special cases listed above).
This implies that each of these fields will be
at least two bits long.
^^ ^^^^^ ^^^ ^^^^ ^^^^
Internet Engineering Task Force [Page 31]
--------------------
Brad Carlson <carlson@mrcnext.cso.uiuc.edu> or <brad-carlson@uiuc.edu>
University of Illinois -- Consultant -- NeXT guru -- Windows Programmer