Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!amdahl!uunet!mcvax!enea!kth!draken!chalmers!cs.chalmers.se!lindberg
From: lindberg@cs.chalmers.se (Gunnar Lindberg)
Newsgroups: comp.unix.wizards
Subject: Re: Setting netmask
Message-ID: <2816@fnatte.cs.chalmers.se>
Date: 30 Dec 88 13:49:42 GMT
References: <17644@adm.BRL.MIL> <272@istsists.ca>
Organization: Dept. of CS, Chalmers, Sweden
Lines: 23

In article <17644@adm.BRL.MIL>, VINCE%UCONNVM.BITNET@cunyvm.cuny.edu writes:
>...
>     In fact this works on the diskless clients (in fact one sees the
>comforting message "Setting the netmask" during the boot process), but
>it does not work on the file server, where the option seems to be
>ignored.

I guess this depends on what SunOS you run, but for 3.x (x >= 4) the
discless clients simply broadcast an "icmp(ICMP_MASKREQ)" on the net
and use the first reply. File servers don't - instead they depend on
"ifconfig" to explicitly set the mask.

The idea of using broadcast has a few disadvantages:

    1)	You may get bad answers (wrong byte order) e.g. from VAXen.
	This was fixed in 3.4.2.

    2)	If the network is large, many hosts may try to answer, which
	gives quite a peak in network traffic (first one ARP for
	each reply, than the reply itself). This was discussed in
	"comp.sys.sun" a while ago.

		Gunnar Lindberg