Path: utzoo!utgpu!watserv1!watmath!att!pacbell!pacbell.com!mips!zaphod.mps.ohio-state.edu!sdd.hp.com!ucsd!ucbvax!BBN.COM!tmallory
From: tmallory@BBN.COM
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Hosts whose IP numbers end in 0........
Message-ID: <9008311622.AA15998@ucbvax.Berkeley.EDU>
Date: 31 Aug 90 12:48:10 GMT
References: <9008292357.AA05692@cincsac.arc.nasa.gov>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 29



> However, the network wide broadcast addresses will always be broadcasts
> and grounds for potential filtering.  Something like 128.102.255.255 will
> always be a broadcast no matter what subnet scheme is in use, unless
> you are doing something really weird(!)...  Packets to this address should
> NEVER be forwarded...

If YOUR router(no interface on 128.89.0.0) ALWAYS filters 128.89.255.255
before MY router sees it, I will have to look elsewhere for transit service.
ALL bits in the host part of the address must be considered to have only local
significance.  The fact that 128.89.255.255 must be recognized as the
broadcast address by all hosts(and routers) on my network allows for
interoperability on my network.  It's nobody else's business.  Packets to this
address MUST never be forwarded when received from an interface on this
network, and MAY never be forwarded to this network if I choose to have them
filtered.

After all that, if this flies in the face of router requirements specified
beyond rfc1009, my apologies.  It doesn't seem right that all one's in the
host field(or all 0's for that matter), is grounds for always filterring
packets to someone else's network.  I probably can accept filtering packets
whose source address is a broadcast address, but I'd prefer that to also be a
local issue.

(Hardware broadcast addresses, on the other hand, need the absolute filtering
we've been talking about.)

Tracy