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From: root@naucse.cse.nau.edu (Paul Balyoz)
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Subnetting and RFC 1101
Keywords: subnetting rfc 1101 host zero
Message-ID: <2858@naucse.cse.nau.edu>
Date: 7 Nov 90 21:59:31 GMT
Organization: Northern Arizona University, Flagstaff AZ
Lines: 36


I have a few questions on Subnetting (and domains) for anyone out there:

Is it legal to use an address for a NETWORK such that the subnet portion
is all zeroes?  For example, suppose that the class-B address 134.114
has been assigned to you, and you use 8-bit subnetting (netmask
is 255.255.255.0).  Does this mean that 134.114.0 can be used as a
legal subnetwork, which can have hosts assigned below it (134.114.0.23),
or must there be a non-zero value for the subnet portion (3rd octet)?

How about 255 for the 3rd octet?  Seems like this should be OK,
because your broadcast address would be 134.114.255.255, which,
with the aforementioned netmask, is only broadcast for the network
134.114.255 .

			     ----------

If this is legal, then I see a problem with the extensions described
by RFC 1101.  Suppose addresses 134.114 are subnetted 255.255.255.0,
but then subnet 134.114.0 is subnetted FURTHER: netmask 255.255.255.248!

Both of those networks would have the SAME HOST-ZERO ADDRESS(!):

		0.0.114.134.in-addr.arpa.

They therefore cannot be described separately in the Domain Name Server
resource-records, the way RFC 1101 says to do it.


Facts/ideas/opinions, anyone?

-- 
Paul Balyoz, Software Specialist II    pab@naucse.cse.nau.edu
Northern Arizona University            root@naucse.cse.nau.edu
PO Box 15600, Flagstaff, AZ 86011      pab%naucse@arizona.edu
NICname for whois: PB1                 ...arizona!naucse!pab