Newbie DNS questions

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Cricket Liu

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Jul 18, 1994, 7:13:07 PM7/18/94
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Jeff Detterman (jlde...@cca.rockwell.com) wrote:

: I just found this newsgroup and thought I would ask a few
: questions:

: 1. Can an object be both a CNAME and an MX record? I need this for
: sites that do not understand MX records.

No. A given domain name can either have a single CNAME RR attached or
multiple other RRs, like A, MX, NS, etc.

: 2. IS "_" valid in a hostname, for example is the name
: road_runner.acme.com a valid name?

I believe so, but I've been a bit weak on valid domain names recently.

: 3. Is it a good idea to run bootp to assign IP addresses? If so
: how does it interact with DNS? Is there another alternative?

Depends on whether your hardware supports BOOTP. If you're using something
with BOOTP support, sure, run BOOTP.

BOOTP doesn't usually interact with DNS. A client queries a BOOTP server to
find all kinds of information, like IP address, default gateways, subnet
mask, hostname, bootfile, etc. The BOOTP server doesn't care whether the
IP address it's assigning really maps to the hostname it's assigning in
DNS, nor does DNS care that BOOTP is giving out the information. I suppose
some vendor may have created a nice system to integrate the management of
these services, but I don't know of one.

: 4. I have pulled down the latest version of bind-4.9.3beta7 and
: compiled it. I have machines that have multiple A records for the same
: name. For example

: thor IN A 131.198.213.10
: thor IN A 131.198.186.11

: nslookup will sequence between the two ip addresses but telnet does
: not. Do I need to recompile telnet in order for this to work? We are
: trying to use this to allow users to telnet to one name and have it
: bounce between different servers in a sequential fashion.

My telnet client (HP-UX 9.01) does. If the first IP address is down,
telnet rolls to the next. Do you want the addresses returned randomly?
That functionality is in BIND 4.9.3, too.

: 5. Does anyone know of a program that would allow multiple users to
: assign themsleves IP addresses. Currntly I use h2n and one static file
: controlled via RCS. I would like to automate this so that non-unix
: users could request/assign IP addresses? Is bootp the answer?

I don't think so. Maybe delegating part of your name space to multiple
users would help, or simply $INCLUDEing other files into your zone data and
letting these users add or delete information from those files. Of course,
they could then add almost anything to your zone....

--
cricket

Hewlett-Packard Professional Services, Englewood, CO

Email: cri...@hp.com
URL: http://babs.nsr.hp.com/~cricket/cricket.html

Message has been deleted

obe...@icaen.llnl.gov

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Jul 18, 1994, 8:58:49 PM7/18/94
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In Article <1994Jul18.2...@zodiac.cca.rockwell.com>

jlde...@cca.rockwell.com (Jeff Detterman) writes:
>
>I just found this newsgroup and thought I would ask a few
>questions:

You should get copies of the relevent specs (RFCs) to get a better idea of
what's allowed. Also the book "DNS ad BIND" from O'Reilly and Assoc. is an
excellent source of information.

>1. Can an object be both a CNAME and an MX record? I need this for
>sites that do not understand MX records.

No. Any name used as a CNAME my not be used otherwise. There is not reason to
ever do so. For systems that don't understand MX records, A records will work
fine. Please note that there is no limit on hte number of A records for a
single address, so just use multiple A entries instead of CNAMEs.

>2. IS "_" valid in a hostname, for example is the name
>road_runner.acme.com a valid name?

BIND has no problem with underscores, but the specification prohibits them, so
it's a good idea not to use them. Hyphens ARE allowed, so road-runnner.acme.com
would be legal.

>3. Is it a good idea to run bootp to assign IP addresses? If so
>how does it interact with DNS? Is there another alternative?

It presents a number of problems. My site does not do any non-permanent address
allocations because there is no clear DNS tracking on what system is what.

>4. I have pulled down the latest version of bind-4.9.3beta7 and
>compiled it. I have machines that have multiple A records for the same
>name. For example
>
>thor IN A 131.198.213.10
>thor IN A 131.198.186.11
>
>nslookup will sequence between the two ip addresses but telnet does
>not. Do I need to recompile telnet in order for this to work? We are
>trying to use this to allow users to telnet to one name and have it
>bounce between different servers in a sequential fashion.

Check the BOG that is with the distribution for Round Robin records. That is
what you are looking for.

>5. Does anyone know of a program that would allow multiple users to
>assign themsleves IP addresses. Currntly I use h2n and one static file
>controlled via RCS. I would like to automate this so that non-unix
>users could request/assign IP addresses? Is bootp the answer?

I generally prefer static assignments. Letting users do their own usually leads
to trouble, but your milage may vary.

R. Kevin Oberman
Energy Sciences Network (ESnet)
National Energy Research Supercomputer Center (NERSC)
Lawrence Livermore National Laboratory (LLNL)
Internet: kobe...@llnl.gov +1 510-422-6955

Jeff Detterman

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Jul 18, 1994, 6:28:49 PM7/18/94
to

I just found this newsgroup and thought I would ask a few
questions:

1. Can an object be both a CNAME and an MX record? I need this for


sites that do not understand MX records.

2. IS "_" valid in a hostname, for example is the name
road_runner.acme.com a valid name?

3. Is it a good idea to run bootp to assign IP addresses? If so

how does it interact with DNS? Is there another alternative?

4. I have pulled down the latest version of bind-4.9.3beta7 and

compiled it. I have machines that have multiple A records for the same
name. For example

thor IN A 131.198.213.10
thor IN A 131.198.186.11

nslookup will sequence between the two ip addresses but telnet does
not. Do I need to recompile telnet in order for this to work? We are
trying to use this to allow users to telnet to one name and have it
bounce between different servers in a sequential fashion.

5. Does anyone know of a program that would allow multiple users to

assign themsleves IP addresses. Currntly I use h2n and one static file
controlled via RCS. I would like to automate this so that non-unix
users could request/assign IP addresses? Is bootp the answer?

Any help would greatly be appreciated.

Thanks

Jeff Detterman

--
Jeff Detterman Rockwell International Commercial Avionics Division
400 Collins RD NE Cedar Rapids, Iowa 319.395.2274 je...@cca.rockwell.com
--------------- Run fast, big dogs bite hard! ----------------------
The views expressed are mine and not my employers.

Per Weisteen

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Jul 19, 1994, 4:05:49 AM7/19/94
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In article <30f2a3$a...@babs.nsr.hp.com>, cri...@nsr.hp.com (Cricket Liu) says:
>
>Jeff Detterman (jlde...@cca.rockwell.com) wrote:
>
(several lines omitted)

>
>: 3. Is it a good idea to run bootp to assign IP addresses? If so
>: how does it interact with DNS? Is there another alternative?
>
>Depends on whether your hardware supports BOOTP. If you're using something
>with BOOTP support, sure, run BOOTP.
>
>BOOTP doesn't usually interact with DNS. A client queries a BOOTP server to
>find all kinds of information, like IP address, default gateways, subnet
>mask, hostname, bootfile, etc. The BOOTP server doesn't care whether the
>IP address it's assigning really maps to the hostname it's assigning in
>DNS, nor does DNS care that BOOTP is giving out the information. I suppose
>some vendor may have created a nice system to integrate the management of
>these services, but I don't know of one.
>

IBM's AIX has a BOOTP daemon that will use DNS for assigning IP addresses.
It's still a one-way solution. If you move equipment to another subnet you
will usually have to edit BOOTP tables to change default gateway etc. The BOOTP
substitute DHCP (RFC 1541) (of which no implementations is freely available..)
ought to have addressed this issue, but didn't. There is definitely need for a
mechanism where DNS could be updated via secure authorized remote transactions.
We have a situation where more and more PC's are assigned IP-addresses
often on a dynamic basis. (DHCP does this for you...) We definitely need a mechanism
where these PC's show up with the same hostname nomatter which IP-address they are
assigned for the moment.


+-----------------------------------------------------------------------+
| Per Weisteen Email: Per.We...@hda.hydro.com |
| Hydro Data Phone: +47 2273 8227 |
| Norsk Hydro "It is better to light a candle, |
| Norway no matter how small, than to curse darkness" |
| Kung-fu-tse |
+-----------------------------------------------------------------------+

Paul A Vixie

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Jul 18, 1994, 10:40:46 PM7/18/94
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>No. A given domain name can either have a single CNAME RR attached or
>multiple other RRs, like A, MX, NS, etc.

It turns out that, due to sloppy code (which in this increasingly rare instance
I inherited rather than wrote), multiple CNAME's also work, and given round
robin, are an interesting way to do load balancing. But don't everybody go out
and use this yet, because I'm considering fixing the bug.
--
Paul Vixie
Redwood City, CA
decwrl!vixie!paul
<pa...@vix.com>

Ian Dickinson

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Jul 19, 1994, 6:04:26 AM7/19/94
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In article <30f2a3$a...@babs.nsr.hp.com>,
cri...@hp.com writes:

>Jeff Detterman (jlde...@cca.rockwell.com) wrote:
>: 2. IS "_" valid in a hostname, for example is the name
>: road_runner.acme.com a valid name?
>I believe so, but I've been a bit weak on valid domain names recently.

It's valid as far as pure Internet stuff is concerned, but seems to break
a number of X.400 gateways. It's much safer to only use alphanumerics and
hyphen, and that won't break anything anywhere that I'm aware of.

Cheers,
--
Ian 'Vato' Dickinson [ID17] Kibo bait :-)
cu...@csv.warwick.ac.uk ...!uknet!warwick!cudep va...@spuddy.uucp
MIME mail welcome - don't send me no steenkin' X.400
Click <A HREF="http://www.csv.warwick.ac.uk/~cudep/">here</A>.

Rainer Schulze

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Jul 19, 1994, 6:34:21 AM7/19/94
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In article c...@spatula.csv.warwick.ac.uk, cu...@csv.warwick.ac.uk (Ian Dickinson) writes:
>In article <30f2a3$a...@babs.nsr.hp.com>,
> cri...@hp.com writes:
>>Jeff Detterman (jlde...@cca.rockwell.com) wrote:
>>: 2. IS "_" valid in a hostname, for example is the name
>>: road_runner.acme.com a valid name?
>>I believe so, but I've been a bit weak on valid domain names recently.
>
>It's valid as far as pure Internet stuff is concerned, but seems to break
>a number of X.400 gateways. It's much safer to only use alphanumerics and
>hyphen, and that won't break anything anywhere that I'm aware of.
>
Of course, it is a problem of interconnecting networks;-)
And not only underscores in hostnames result in problems
at some X.400/SMTP-gateways, but also underscores in
the local part of an email address like
firstname...@some.dom.ain.

Thus avoid not only underscores in hostnames but also in
any part of your email address until all gateways have no
problems with underscores. (Don't know when this will be;-)))


---
Rainer Schulze PHONE: +49 30 / 89604-187
Konrad-Zuse-Zentrum fuer EMAIL: Sch...@ZIB-Berlin.DE
Informationstechnik Berlin (ZIB) FAX: +49 30 / 89604-125
Heilbronner Str. 10
D-10711 Berlin-Wilmersdorf


Chris Walsh

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Jul 19, 1994, 11:47:46 AM7/19/94
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In article <30g1gt$2r...@vkhdib01.hda.hydro.com>,

Per Weisteen <Per.We...@hda.hydro.com> wrote:
>
>IBM's AIX has a BOOTP daemon that will use DNS for assigning IP addresses.
>It's still a one-way solution. If you move equipment to another subnet you
>will usually have to edit BOOTP tables to change default gateway etc. The BOOTP
>substitute DHCP (RFC 1541) (of which no implementations is freely available..)
>ought to have addressed this issue, but didn't. There is definitely need for a
>mechanism where DNS could be updated via secure authorized remote transactions.
>We have a situation where more and more PC's are assigned IP-addresses
>often on a dynamic basis. (DHCP does this for you...) We definitely need a mechanism
>where these PC's show up with the same hostname nomatter which IP-address they are
>assigned for the moment.


I apologize if this is a shade off-topic for this newsgroup, but I was
wondering if anyone is aware of any work in progress which addresses the
need Mr. Weisteen is pointing out. A colleague of mine was thinking of
writing up some code (in his copious free time :^)), but if there's
already a solution in the works, I'd very much like to hear of it.

Chris Walsh

Tim Goodwin

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Jul 19, 1994, 1:06:50 PM7/19/94
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In article <30g8fa$c...@spatula.csv.warwick.ac.uk>, Ian Dickinson

<cu...@csv.warwick.ac.uk> wrote:
>In article <30f2a3$a...@babs.nsr.hp.com>, cri...@hp.com writes:
>>: 2. IS "_" valid in a hostname, for example is the name
>>: road_runner.acme.com a valid name?
>>I believe so, but I've been a bit weak on valid domain names recently.
>
>It's valid as far as pure Internet stuff is concerned, but seems to break
>a number of X.400 gateways. It's much safer to only use alphanumerics and
>hyphen, and that won't break anything anywhere that I'm aware of.

I hesitate to contradict two people whose opinions I respect as much
as Ian and Cricket, but, well, are you sure?

RFC-952 seems fairly clear to me.

1. A "name" (Net, Host, Gateway, or Domain name) is a text string up
to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus
sign (-), and period (.). Note that periods are only allowed when
they serve to delimit components of "domain style names". (See
RFC-921, "Domain Name System Implementation Schedule", for
background). No blank or space characters are permitted as part of a
name. No distinction is made between upper and lower case. The first
character must be an alpha character. The last character must not be
a minus sign or period. [...]

RFC-1123 references this definition, and modifies it slightly: the first
character may now be a numeric character (as in 1776.com, for example).

Although BIND will happily handle names with underscores, dnswalk picks
up the error.

[ I'm slightly puzzled by the 24 character restriction. Although
RFC-1123 states that host software should handle names up to 255
characters, it doesn't explicitly say that this is a modification to
RFC-952. ]

Tim.
--
Tim Goodwin | "Any time *anything* goes wrong on a
Public IP Exchange | PC, I immediately suspect a hardware
Cambridge, UK | problem :-)." -- Chris Torek

Tim Goodwin

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Jul 19, 1994, 1:16:58 PM7/19/94
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In article <1994Jul18.2...@zodiac.cca.rockwell.com>,

Jeff Detterman <jlde...@cca.rockwell.com> wrote:
>1. Can an object be both a CNAME and an MX record? I need this for
>sites that do not understand MX records.

<pedantic>

A host which does SMTP but does not understand MX records is in
violation of a MUST clause in RFC-1123 (section 5.3.5). RFC-1123 is a
required Internet standard. Such a host, therefore, is not suitable
for connection to the Internet.

<\pedantic>

Seriously, these hosts are either misconfigured (maybe they forgot to
use sendmail.mx, if it's a Sun system) or hopelessly broken. In either
case, you should not be wasting *your* time fixing *their* problem.

Cricket Liu

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Jul 19, 1994, 4:40:42 PM7/19/94
to
Tim Goodwin (t...@pipex.net) wrote:
: In article <30g8fa$c...@spatula.csv.warwick.ac.uk>, Ian Dickinson

: <cu...@csv.warwick.ac.uk> wrote:
: >In article <30f2a3$a...@babs.nsr.hp.com>, cri...@hp.com writes:
: >>: 2. IS "_" valid in a hostname, for example is the name
: >>: road_runner.acme.com a valid name?
: >>I believe so, but I've been a bit weak on valid domain names recently.
: >
: >It's valid as far as pure Internet stuff is concerned, but seems to break
: >a number of X.400 gateways. It's much safer to only use alphanumerics and
: >hyphen, and that won't break anything anywhere that I'm aware of.

: I hesitate to contradict two people whose opinions I respect as much
: as Ian and Cricket, but, well, are you sure?

I appreciate the respect, but you're quite right, and I'm quite wrong! ;-)

I couldn't remember whether it was the use of underscores or dashes which
was deprecated, and--just like last time--I mixed them up.

Does anyone know why underscores are verboten and dashes are alright?

Russell Nelson

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Jul 20, 1994, 10:53:10 AM7/20/94
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In article <30f2a3$a...@babs.nsr.hp.com> cri...@nsr.hp.com (Cricket Liu) writes:

Cricket is being modest. If you have questions about the DNS, you
can't go wrong with the O'Reilly and Associates _DNS and Bind_,
written by Paul Albitz & Cricket Liu.

The BOOTP server doesn't care whether the IP address it's assigning
really maps to the hostname it's assigning in DNS, nor does DNS
care that BOOTP is giving out the information. I suppose some
vendor may have created a nice system to integrate the management
of these services, but I don't know of one.

Here's some code I wrote for a customer. It's public domain. It
parses a named input file, looking for special comments. Here's an
example of the input. The host's IP address is remembered, and
combined with the Ethernet address on the BOOTP comment line.

ray8180 IN A 137.143.111.245
; BOOTP 000094573758
ray8152 IN A 137.143.111.246
; BOOTP AA000400A34F
ray8153 IN A 137.143.111.247
; BOOTP AA000400A44F
ray9154 IN A 137.143.111.248
; BOOTP AA000400A24F


#! /bin/sh
# This file is /usr/lib/named/makebootptab
# create /etc/bootptab from /etc/bootptab.head and /var/dss/namedb/named.potsdam
cat /etc/bootptab.head >/tmp/bootptab
nawk '$2 == "IN" {
host = $1
ip = $4
}

$2 == "BOOTP" {
if ($3 in addr_to_host) {
print "# Duplicate hardware address " $3 " for " host " and " addr_to_host[$3]
} else {
addr_to_host[$3] = host
}
printf("%s:tc=global.dummy:ht=ethernet:ha=%s:ip=%s:\n", host, $3, ip);
}' /var/dss/namedb/named.potsdam >>/tmp/bootptab

mv /etc/bootptab /etc/bootptab.bak
mv /tmp/bootptab /etc/bootptab
exit 0


#and this is all that needs to be in /etc/bootptab.head:
global.dummy:\
:sm=255.255.252.0:\
:ds=137.143.110.101:\
:gw=137.143.110.254:\
:to=18000:

--
-russ <nel...@crynwr.com> http://www.crynwr.com/crynwr/nelson.html
Crynwr Software | Crynwr Software sells packet driver support | ask4 PGP key
11 Grant St. | +1 315 268 1925 (9201 FAX) | What is thee doing about it?
Potsdam, NY 13676 | LPF member - ask me about the harm software patents do.

Robert A. Rosenberg

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Jul 22, 1994, 12:07:49 AM7/22/94
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In Article <30hdoa$c...@babs.nsr.hp.com>, cri...@nsr.hp.com (Cricket Liu) wrote:

>Does anyone know why underscores are verboten and dashes are alright?
>


Taking a wild stab, I'd guess that it maybe has something to do with "_" not
making it though all gateways without being code converted into a form that
will not map back to "_". This (if I am SWAGing correctly) is the same
problem that would place this character on the list to be Quoted in MIME QP
format. I am just guessing and I've _not_ verified this with the list of
"transparent"/"non-transparent" characters in the MIME RFCs.

Paul A Vixie

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Jul 21, 1994, 7:50:05 PM7/21/94
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Most of the time I can make a bootptab just by perl-postprocessing "arp -a".

Tim Goodwin

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Jul 27, 1994, 7:37:45 AM7/27/94
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In article <30hdoa$c...@babs.nsr.hp.com>, Cricket Liu <cri...@hp.com> wrote:
>Does anyone know why underscores are verboten and dashes are alright?

Allowing both would be far too confusing.

Tim.
--
Tim Goodwin | If alt is the sewer of Usenet,
Public IP Exchange | com is the sewer of the DNS.

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