Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ucbvax!ANDREW.CMU.EDU!ddp+
From: ddp+@ANDREW.CMU.EDU (Drew Daniel Perkins)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: bootp/rarp
Message-ID: <IVvafXy00UoJJq40C9@andrew.cmu.edu>
Date: 15 Jan 88 19:24:19 GMT
References: <1957@munnari.oz>
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
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I'm pretty sure that the original 4.2bsd only supported net.0.  I'm sure Mike 
Karel's will correct me if I'm wrong...  We were faced with the same problem 
when we implemented a BOOTP for PCIP (IBMPC).  My solution was to use 
255.255.255.255 as the defautl, as was specified by the RFC.  However I left a 
hook to extend it to net.0 if desired.  With PCIP, the IP address is normally 
stored on a disk and is loaded into memory at boot time.  All programs use the 
IP address in memory, not the disk.  Thus, my BOOTP program modified the IP 
address in memory after it found the address.  However, it figures out which 
broadcast address to use by seeing what is in memory when it starts, which is 
the IP address on the disk.  If the address is 0.0.0.0, it uses the default of 
255.255.255.255.  However, if it is stored as net.0 or net.subnet.0, it uses 
that as the address.  This is not per the spec, but I couldn't think of 
anything it would break.  Currently all of our PC's are configured to use 
128.2.0.0 since we still have plenty of 4.2 machines.  Of course if you are 
using a ROM and can't even store this much info (i.e. you don't have an EEPROM 
or battery backed up memory or...) then I don't think there is going to be 
much you can do.

Drew