Path: utzoo!attcan!uunet!lll-winken!ncis.tis.llnl.gov!helios.ee.lbl.gov!pasteur!ucbvax!DSYS.ICST.NBS.GOV!rbj
From: rbj@DSYS.ICST.NBS.GOV (Root Boy Jim)
Newsgroups: comp.protocols.tcp-ip
Subject: Reconciling /etc/hosts, yp, and named?
Message-ID: <8905161521.AA02497@dsys.icst.nbs.gov>
Date: 16 May 89 15:21:12 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: National Institute of Standards and Technology
	formerly National Bureau of Standards
Lines: 64

? From: steve@umiacs.umd.edu (Steven D. Miller)

?    It seems to me that the following combinations of DNS/YP/host table usage
? are valid:

? 	1) You're using the domain name system.  In this case, *all* host
? 	lookups should go through the DNS.  The only exception here is that
? 	at boot time, you'll need to be able to fall back on the host table
? 	so that you can do a host name lookup to configure your network
? 	interface.  Other than that, you *never* fall back on the host
? 	tables, as host table information is out-of-date, wrong, and won't
? 	be around for too much longer.  I'd rather have no answer than a
? 	wrong one, though I suppose this is something of a religious issue.

True. I would like to add one more belief to our religion. I would
caution against using the host tables even to bring the network up.
First, consider a gateway, with two interfaces with two different
IP addresses but only one name. You obviously can't do:

	ifconfig ie0 foo.bar.com
	ifconfig ie1 foo.bar.com

Now perhaps one could (and should?) define a foo-gw.bar.com address, but
the order of addresses in /etc/hosts will determine which IP address is
returned first, so you really need three names, especially if you are
using the same host table on multiple hosts on multiple subnets. Simpler
to just use one name, and use naked IP addresses on the ifconfigs.

Now consider a host on an subnet with only one gateway to the rest of
the would. It needs a `route add default <gateway> 1' line. Again,
the order of the entrys in the host table will determine which IP
address is returned first. Another good place to use IP addresses.

? 		(Note that it's important for your customers to be able to
? 		purge YP entirely from their systems without causing any
? 		catastrophes.)

This is an important point. So far, Sun has amazingly shown great
restraint in not forcing YP down everyone's throat. As far as I know,
YP has nothingh to do with the Arpanet Reference Model. It is a
proprietary service, an RFC has not been written for it, and there is
no mention in any of the host requirements for or of it.

True, it is found in other vendor's implementations of NFS; Sequent,
for example, has all the YP stuff in it's NFS librarys. It is my
belief that for such vendors it is easier to just take the whole
package than to split off just the good parts. Besides, they paid
for it anyway, and too much software is better than not enuf,
especially if you can throw the excess away.

However, there remains a significant number of people out there (Steve
and myself, among others) which are constitutionally opposed to YP.
We will certainly not use it in its current form and may never use it
in any form whatsoever.

? 	-Steve

? Spoken: Steve Miller    Domain: steve@mimsy.umd.edu    UUCP: uunet!mimsy!steve
? Phone: +1-301-454-1808  USPS: UMIACS, Univ. of Maryland, College Park, MD 20742

ESIG2WIDE.

	Root Boy Jim is what I am
	Are you what you are or what?