Q: Help ! How do I use the Completely new configuration syntax in BIND 8 ? I've attempted to upgrade bind from 4.9.5 to 8.1, but unfortunately it didn't seem to like the same config/zone files.. is this normal or should 8.1 be able to read the same files as 4.9.5 did?
A: If you then look in doc/html/config.html, you will find directions
on how to convert a 4.9.x .boot file to 8.x .conf file, as well as
directions on how to utilize all of the new features of the 8.x .conf file format.
Question 5.2. Changing a Secondary server to a Primary server
?
Date: Fri Jul 5 23:54:35 EDT 1996
For 4.8.3, it's prudent to kill and restart following any changes to named.boot.
In BIND 4.9.3, you only have to kill and restart named if you change a primary zone to a secondary or v-v, or if you delete a zone and remain authoritative for its parent. Every other case should be taken care of by a HUP. (Ed. note: 4.9.3b9 may still require you to kill and restart the server due to some bugs in the HUP code).
You will also need to update the server information on the root
servers. You can do this by filing a new domain registration form to inform
InterNIC of the change. They will then update the root server's SOA
records. This process usually takes 10-12 business days after they
receive the request.
Question 5.3. Moving a Primary server to another
server
Date: Fri Jul 5 23:54:35 EDT 1996
The usual solution is to move the primary to ns.newserver.com, and have ns.oldserver.com be configured as a secondary server until the change to the root servers takes place after the request has been made to the InterNIC.
If you are moving to a different ISP which will change your IP's, the recommend setting for the SOA that would minimize problems for your name servers using the old settings can be done as follows:
Gradually lower the TTL value in your SOA (that's the last one of the five numbers) to always be equal to the time left until you change over. (assuming that none of your resource records have individual TTL's set, if so, do likewise with them.) So, the day before, lower to 43200 seconds (12 hours). Then lower every few hours to be the time remaining until the change-over. So, an hour before the change, you may just want to lower it all the way to 60 seconds or so. That way no one can cache information past the change-over.
After the change, start gradually incrementing the TTL value, because you'll probably be making changes to work out problems. Once everything stabilizes, move the TTL up to whatever your normal values are.
To minimize name servers from using the "old settings", you can do the same thing with the "refresh" interval in the SOA (the second number of the SOA). That will tell the secondaries to refresh every X seconds. Lower that value as you approach the changeover date. You probably don't want to go much below an hour or you'll start the primary thrashing as all the secondaries perpetually refresh.
Also see the answer to the "How can I change the IP address of
our server ?" in the INTRODUCTION section.
Question 5.4. How do I subnet a Class B Address
?
Date: Mon Jun 15 23:21:39 EDT 1998
That you need to subnet at all is something of a misconception. You can also think of a class B network as giving you 65,534 individual hosts, and such a network will work. You can also configure your class B as 16,384 networks of 2 hosts each. That's obviously not very practical, but it needs to be made clear that you are not constrained by the size of an octet (remember that many older devices would not work in a network configured in this manner).
So, the question is: why do you need to subnet? One reason is that it is easier to manage a subnetted network, and in fact, you can delegate the responsibility for address space management to local administrators on the various subnets. Also, IP based problems will end up localized rather than affecting your entire network.
If your network is a large backbone with numerous segments individually branching off the backbone, that too suggests subnetting.
Subnetting can also be used to improve routing conditions.
You may wish to partition your network to disallow certain protocols on certain segments of your net. You can, for example, restrict IP or IPX to certain segments only by adding a router routing high level protocols, and across the router you may have to subnet.
Finally, as far as how many subnets you need depends on the answer to the above question. As far as subnet masks are concerned, the mask can be anything from 255.0.0.0 to 255.255.255.252. You'll probably be looking at 9 or 10 bits for the subnet (last octet 128 or 192 respectively). RFC 1219 discusses the issue of subnetting very well and leaves the network administrator with a large amount of flexibility for future growth.
(The following section was contributed by Berislav Todorovic.)
A user or an ISP, having a whole /16 sized IP block (former "Class B") network assigned/allocated, has the responsibility of maintaining the reverse domain for the whole network. That policy is currently applied by all regional Internet registries (RIPE NCC, ARIN, APNIC). In other words, if you're assigned a whole "B class" (say, 10.91/16), you're in charge for the whole 91.10.IN-ADDR.ARPA zone. This zone may be organized using two methods, according to the network topology being in use.
The first, "brute force" method is to place all PTR records directly into a single zone file. Example:
$origin 91.10.in-addr.arpa
@ IN SOA (usual stuff)
IN NS ns1.mydomain.com.
IN NS ns2.mydomain.com.
1.1 IN PTR one-1.mydomain.com. ; ---> 10.91.1.1
2.1 IN PTR one-2.mydomain.com. ; ---> 10.91.1.2
...
254.1 IN PTR one-254.mydomain.com. ; ---> 10.91.1.254
1.2 IN PTR two-1.mydomain.com. ; ---> 10.91.2.1
While this approach may look simple in the networks with a central
management authority (say, campus networks), maintaining such a zone
file becomes more and more difficult in the more complex environment.
Thus, this becomes a bad method. Furthermore, if you're an ISP, it is
more likely that a /16 network will be subnetted and its subnets be
assigned to your customers.
Therefore, another "smarter" approach is to delegate portions of the reverse domain 91.10.IN-ADDR.ARPA to the end users of the subnets of 10.91/16. There would only be NS records in the zone file, while PTR record insertion would be the responsibility of the end users. For example, if you assign:
* 10.91.0.0/22 (10.91.0.0 - 10.91.3.255) to Customer-A.COM * 10.91.4.0/23 (10.91.4.0 - 10.91.5.255) to Customer-B.COM * 10.91.7.0/24 (10.91.7.0 - 10.91.7.255) to Customer-C.COMthen each customer will maintain zone files for the reverse domains of their own networks (say, Customer C will maintain the zone 7.91.10.IN-ADDR.ARPA, customer B their 2 zones, Customer A their own 4 zones). In this constellation, the zone file for reverse domain 91.10.IN-ADDR.ARPA will look like this:
$origin 91.10.in-addr.arpa
@ IN SOA (usual stuff)
IN NS ns1.mydomain.com.
IN NS ns2.mydomain.com.
; --- Customer-A.COM
0 IN NS ns.customer-A.com.
IN NS ns1.mydomain.com.
1 IN NS ns.customer-A.com.
IN NS ns1.mydomain.com.
2 IN NS ns.customer-A.com.
IN NS ns1.mydomain.com.
3 IN NS ns.customer-A.com.
IN NS ns1.mydomain.com.
; --- Customer-B.COM
4 IN NS ns.customer-B.com.
IN NS ns1.mydomain.com.
5 IN NS ns.customer-B.com.
IN NS ns1.mydomain.com.
; --- Customer-C.COM
7 IN NS ns.customer-C.com.
IN NS ns1.mydomain.com.
The zone file of the Customer C reverse domain would look like this:
$origin 7.91.10.in-addr.arpa
@ IN SOA (usual stuff)
IN NS ns.customer-C.com.
IN NS ns1.mydomain.com.
1 IN PTR one.customer-C.com.
2 IN PTR two.customer-C.com.
3 IN PTR three.customer-C.com.
...
If you are looking for some examples of handling subnetted class C networks as separate DNS domains, see RFC 2317 for more information.
Details follow- You need to delegate down to the fourth octet, so you will have one domain per IP address ! Here is how you can subdelegate a in-addr.arpa address for non-byte aligned subnet masks:
Take as an example the net 192.1.1.x, and example subnet mask 255.255.255.240.
We first define the domain for the class C net,
$origin 1.1.192.in-addr.arpa
@ SOA (usual stuff)
@ ns some.nameserver
ns some.other.nameserver
; delegate a subdomain
one ns one.nameserver
ns some.nameserver
; delegate another
two ns two.nameserver
ns some.nameserver
; CNAME pointers to subdomain one
0 CNAME 0.one
1 CNAME 1.one
; through
15 CNAME 15.one
; CNAME pointers to subdomain two
16 CNAME 16.two
17 CNAME 17.two
31 CNAME 31.two
; CNAME as many as required.
Now, in the delegated nameserver, one.nameserver
$origin one.1.1.192.in-addr.arpa
@ SOA (usual stuff)
NS one.nameserver
NS some.nameserver ; secondary for us
0 PTR onenet.one.domain
1 PTR onehost.one.domain
; through
15 PTR lasthost.one.domain
And similar for the two.1.1.192.in-addr.arpa delegated domain.
There is additional documentation and a perl script that may be used for this purpose available for anonymous ftp from:
ftp.is.co.za : /networking/ip/dns/gencidrzone/gencidrzone
Question 5.6. Recommended format/style of DNS
files
Date: Sun Nov 27 23:32:41 EST 1994
This answer is quoted from an article posted by Paul Vixie:
I've gone back and forth on the question of whether the BOG should
include a section on this topic. I know what I myself prefer, but
I'm wary of ramming my own stylistic preferences down the throat of
every BOG reader. But since you ask :-)...
Create /var/named. If your system is too old to have a /var, either
create one or use /usr/local/adm/named instead. Put your named.boot
in it, and make /etc/named.boot a symlink to it. If your system
doesn't have symlinks, you're S-O-L (but you knew that). In
named.boot, put a "directory" directive that specifies your actual
BIND working directory:
directory /var/named
All relative pathnames used in "primary", "secondary", and "cache"
directives will be evaluated relative to this directory. Create two
subdirectories, /var/named/pri and /var/named/sec. Whenever you add
a "primary" directive to your named.boot, use "pri/WHATEVER" as the
path name. And then put the primary zone file into "pri/WHATEVER".
Likewise when you add "secondary" directives, use "sec/WHATEVER" and
BIND (really named-xfer) will create the files in that
subdirectory.
(Variations: (1) make a midlevel directory "zones" and put "pri" and
"sec" into it; (2) if you tend to pick up a lot of secondaries from
a few hosts, group them together in their own subdirectories --
something like /var/named/zones/uucp if you're a UUCP Project name
server.)
For your forward files, name them after the zone. dec.com becomes
"/var/named/zones/pri/dec.com". For your reverse files, name them
after the network number. 0.1.16.in-addr.arpa becomes
"/var/named/zones/pri/16.1.0".
When creating or maintaining primary zone files, try to use the same
SOA values everywhere, except for the serial number which varies per
zone. Put a $ORIGIN directive at the top of the primary zone file,
not because its needed (it's not since the default origin is the
zone named in the "primary" directive) but because it make it easier
to remember what you're working on when you have a lot of primary
zones. Put some comments up there indicating contact information
for the real owner if you're proxying. Use RCS and put the "Id"
in a ";" comment near the top of the zone file.
The SOA and other top level information should all be listed
together. But don't put IN on every line, it defaults nicely. For
example:
==============
@ IN SOA gw.home.vix.com. postmaster.vix.com. (
1994082501 ; serial
3600 ; refresh (1 hour)
1800 ; retry (30 mins)
604800 ; expire (7 days)
3600 ) ; minimum (1 hour)
NS gw.home.vix.com.
NS ns.uu.net.
NS uucp-gw-1.pa.dec.com.
NS uucp-gw-2.pa.dec.com.
MX 10 gw.home.vix.com.
MX 20 uucp-gw-1.pa.dec.com.
MX 20 uucp-gw-1.pa.dec.com.
==============
I don't necessarily recommend those SOA values. Not every zone is
as volatile as the example shown. I do recommend that serial number
format; it's in date format with a 2-digit per-day revision number.
This format will last us until 2147 A.D. at which point I expect a
better solution will have been found :-). (Note that it would last
until 4294 A.D. except that there are some old BINDs out there that
use a signed quantity for representing serial number internally; I
suppose that as long as none of these are still running after 2047
A.D., that we can use the above serial number format until 4294
A.D., at which point a better solution will HAVE to be found.)
You'll note that I use a tab stop for "IN" even though I never again
specify it. This leaves room for names longer than 7 bytes without
messing up the columns. You might also note that I've put the MX
priority and destination in the same tab stop; this is because both
are part of the RRdata and both are very different from MX which is
an RRtype. Some folks seem to prefer to group "MX" and the priority
together in one tab stop. While this looks neat it's very confusing
to newcomers and for them it violates the law of least
astonishment.
If you have a multi-level zone (one which contains names that have
dots in them), you can use additional $ORIGIN statements but I
recommend against it since there is no "back" operator. That is,
given the above example you can add:
=============
$ORIGIN home
gw A 192.5.5.1
=============
The problem with this is that subsequent RR's had better be
somewhere under the "home.vix.com" name or else the $ORIGIN that
introduces them will have to use a fully qualified name. FQDN
$ORIGIN's aren't bad and I won't be mad if you use them.
Unqualified ones as shown above are real trouble. I usually stay
away from them and just put the whole name in:
=============
gw.home A 192.5.5.1
=============
In your reverse zones, you're usually in some good luck because the
owner name is usually a single short token or sometimes two.
=============
$ORIGIN 5.5.192.in-addr.arpa.
@ IN SOA ...
NS ...
1 PTR gw.home.vix.com.
=========================================
$ORIGIN 1.16.in-addr.arpa.
@ IN SOA ...
NS ...
2.0 PTR gatekeeper.dec.com.
=============
It is usually pretty hard to keep your forward and reverse zones in
sync. You can avoid that whole problem by just using "h2n" (see
the ORA book, DNS and BIND, and its sample toolkit, included in the
BIND distribution or on ftp.uu.net (use the QUOTE SITE EXEC INDEX
command there to find this -- I never can remember where it's at).
"h2n" and many tools like it can just read your old /etc/hosts file
and churn it into DNS zone files. (May I recommend
contrib/decwrl/mkdb.pl from the BIND distribution?) However, if you
(like me) prefer to edit these things by hand, you need to follow
the simple convention of making all of your holes consistent. If
you use 192.5.5.1 and 192.5.5.3 but not (yet) 192.5.5.2, then in
your forward file you will have something like
=============
...
gw.home A 192.5.5.1
;avail A 192.5.5.2
pc.home A 192.5.5.3
=============
and in your reverse file you will have something like
=============
...
1 PTR gw.home.vix.com.
;2 PTR avail
3 PTR pc.home.vix.com.
=============
This convention will allow you to keep your sanity and make fewer
errors. Any kind of automation (h2n, mkdb, or your own
perl/tcl/awk/python tools) will help you maintain a consistent
universe even if it's also a complex one. Editing by hand doesn't
have to be deadly but you MUST take care.
You need to create your own root domain name server until you connect to the internet. Your roots need to delegate to mydomain.com and any in-addr.arpa subdomains you might have, and that's about it. As soon as you're connected, rip out the fake roots and use the real ones.
It does not actually have to be another server pretending to be the root. You can set up the name server so that it is primary for each domain above you and leave them empty (i.e. you are foo.bar.com - claim to be primary for bar.com and com)
If you connect intermittently and want DNS to work when you are
connected, and "fail" when you are not, you can point the resolver at
the name server at the remote site and if the connection (SLIP/PPP) isn't up, the
resolver doesn't have a route to the remote server and since there's only one
name server in resolv.conf, the resolver quickly backs off the using
/etc/hosts. No problem. You could do the same with multiple name server and a
resolver that did configurable /etc/hosts fallback.
Question 5.8. Multiple Domain configuration
Date: Fri Dec 2 15:40:49 EST 1994
If you want to have multiple domain names pointing to the same destination, such as:
ftp ftp.biff.com connects user to -> ftp.biff.com
ftp ftp.fred.com connects user to -> ftp.biff.com
ftp ftp.bowser.com connects user to -> ftp.biff.com
You may do this by using CNAMEs:
ftp.bowser.com. IN CNAME ftp.biff.com.
You can also do the same thing with multiple A records.
Does BIND not understand wildcard MX records such as the following?
*.foo.com MX 0 mail.foo.com.
No. It just doesn't work.
Explicit RR's at one level of specificity will, by design, "block" a wildcard at a lesser level of specificity. I suspect that you have an RR (an A RR, perhaps?) for "bar.foo.com" which is blocking the application of your "*.foo.com" wildcard. The initial MX query is thus failing (NOERROR but an answer count of 0), and the backup query finds the A RR for "bar.foo.com" and uses it to deliver the mail directly (which is what you DIDN'T want it to do). Adding an explicit MX RR for the host is therefore the right way to handle this situation.
See RFC 1034, Section 4.3.3 ("Wildcards") for more information on this "blocking" behavior, along with an illustrative example. See also RFC 974 for an explanation of standard mailer behavior in the face of an "empty" response to one's MX query.
Basically, what it boils down to is, there is no point in trying to use a wildcard MX for a host which is otherwise listed in the DNS.
It just doesn't work.
Question 5.10. How do you identify a wildcard MX record
?
Date: Thu Dec 1 11:10:39 EST 1994
You don't really need to "identify" a wildcard MX RR. The precedence for u@dom is:
exact match MX
exact match A
wildcard MX
One way to implement this is to query for ("dom",IN,MX) and
if the answer name that comes back is "*." something, you know it's
a wildcard, therefore you know there is no exact match MX, and you
therefore query for ("dom",IN,A) and if you get something,
use it. if you don't, use the previous wildcard response.
RFC 974 explains this pretty well.
Question 5.11. Why are fully qualified domain names recommended
?
Date: Sun Nov 27 23:32:41 EST 1994
The documentation for BIND 4.9.2 says that the hostname should be set to the full domain style name (i.e host.our.domain rather than host). What advantages are there in this, and are there any adverse consequences if we don't?
Paul Vixie likes to do it :-) He lists a few reasons -
gethostbyname(gethostname) == gethostbyaddr(primary_interface_address)
If you take an address and go "backwards" through the PTR's
with it, you'll get a FQDN, and if you push that back through the A
RR's, you get the same address. Or you should. Many multi-homed
hosts violate this uncaringly.
If you take a non-FQDN hostname and push it "forwards" through the A RR's, you get an address which, if you push it through the PTR's, comes back as a FQDN which is not the same as the hostname you started with. Consider the fact that, absent NIS/YP, there is no "domainname" command analogous to the "hostname" command. (NIS/YP's doesn't count, of course, since it's sometimes-but-only-rarely the same as the Internet domain or subdomain above a given host's name.) The "domain" keyword in resolv.conf doesn't specify the parent domain of the current host; it specifies the default domain of queries initiated on the current host, which can be a very different thing. (As of RFC 1535 and BIND 4.9.2's compliance with it, most people use "search" in resolv.conf, which overrides "domain", anyway.)
What this means is that there is NO authoritative way to programmatically discover your host's FQDN unless it is set in the hostname, or unless every application is willing to grovel the "netstat -in" tables, find what it hopes is the primary address, and do a PTR query on it.
FQDN /bin/hostnames are, intuitively or not, the simplest way to go.
When you attempt to distribute the load on a system using named, the first response be cached, and then later queries use the cached value (This would be for requests that come through the same server). Therefore, it can be useful to use a lower TTL on records where this is important. You can use values like 300 or 500 seconds.
If your local caching server has ROUND_ROBIN, it does not matter what the authoritative servers have -- every response from the cache is rotated.
But if it doesn't, and the authoritative server site is depending on this feature (or the old "shuffle-A") to do load balancing, then if one doesn't use small TTLs, one could conceivably end up with a really nasty situation, e.g., hundreds of workstations at a branch campus pounding on the same front end at the authoritative server's site during class registration.
Not nice.
Paul Vixie has an example of the ROUND_ROBIN code in action. Here is something that he wrote regarding his example:
I want users to be distributed evenly among those 3 hosts.
Believe it or not :-), BIND offers an ugly way to do this. I offer
for your collective amusement the following snippet from the
ugly.vix.com zone file:
hydra cname hydra1
cname hydra2
cname hydra3
hydra1 a 10.1.0.1
a 10.1.0.2
a 10.1.0.3
hydra2 a 10.2.0.1
a 10.2.0.2
a 10.2.0.3
hydra3 a 10.3.0.1
a 10.3.0.2
a 10.3.0.3
Note that having multiple CNAME RR's at a given name is
meaningless according to the DNS RFCs but BIND doesn't mind (in
fact it doesn't even complain). If you call
gethostbyname("hydra.ugly.vix.com") (try it!) you will get
results like the following. Note that there are two round robin
rotations going on: one at ("hydra",CNAME) and one at each
("hydra1",A) et al. I used a layer of CNAME's above the layer of
A's to keep the response size down. If you don't have nine
addresses you probably don't care and would just use a pile of
CNAME's pointing directly at real host names.
{hydra.ugly.vix.com
name: hydra2.ugly.vix.com
aliases: hydra.ugly.vix.com
addresses: 10.2.0.2 10.2.0.3 10.2.0.1
{hydra.ugly.vix.com
name: hydra3.ugly.vix.com
aliases: hydra.ugly.vix.com
addresses: 10.3.0.2 10.3.0.3 10.3.0.1
{hydra.ugly.vix.com
name: hydra1.ugly.vix.com
aliases: hydra.ugly.vix.com
addresses: 10.1.0.2 10.1.0.3 10.1.0.1
{hydra.ugly.vix.com
name: hydra2.ugly.vix.com
aliases: hydra.ugly.vix.com
addresses: 10.2.0.3 10.2.0.1 10.2.0.2
{hydra.ugly.vix.com
name: hydra3.ugly.vix.com
aliases: hydra.ugly.vix.com
addresses: 10.3.0.3 10.3.0.1 10.3.0.2
Please note that this is not a recommended practice and will not work
with modern BIND unless you have the entry "multiple-cnames yes"
in your named.conf file.
Round robin != load balancing. It's a very crude attempt at load balancing, and a method that is possible without breaking DNS protocols. If a host is down that is included in a round robin list, then connections to that particular host will fail. In addition, true load balancing should take into consideration the actual LOAD on the system.
Information on one such technique, implemented by Roland J. Schemers III at Stanford, may be found at http://www-leland.stanford.edu/~schemers/docs/lbnamed/lbnamed.html.
Additional information may be found in RFC 1794. MultiNet for OpenVMS also includes this feature.
Question 5.14. Order of returned records
Date: Tue Apr 8 20:21:02 EDT 1997
Sorting, is the *resolver's* responsibility. RFC 1123:
6.1.3.4 Multihomed Hosts
When the host name-to-address function encounters a host
with multiple addresses, it SHOULD rank or sort the
addresses using knowledge of the immediately connected
network number(s) and any other applicable performance or
history information.
DISCUSSION:
The different addresses of a multihomed host generally
imply different Internet paths, and some paths may be
preferable to others in performance, reliability, or
administrative restrictions. There is no general way
for the domain system to determine the best path. A
recommended approach is to base this decision on local
configuration information set by the system
administrator.
In BIND 4.9.x's resolver code, the "sortlist" directive in
resolv.conf can be used to configure this. The directive may also be used in the
named.boot as well.
The question was asked one time, "Why should I use 'real' IP addresses in /etc/resolv.conf and not 0.0.0.0 or 127.0.0.1" ?
Paul Vixie writes on the issue of the contents of resolv.conf:
It's historical. Some kernels can't unbind a UDP socket's source address, and some resolver versions (notably not including BIND 4.9.2 or 4.9.3's) try to do this. The result can be wide area network traffic with 127.0.0.1 as the source address. Rather than giving out a long and detailed map of version/vendor combinations of kernels/BINDs that have/don't this problem, I just tell folks not to use 127.0.0.1 at all. 0.0.0.0 is just an alias for the first interface address assigned after a system boot, and if that interface is a up-and-down point to point link (PPP, SLIP, whatever), there's no guarantee that you'll be able to reach yourself via 0.0.0.0 during the entire lifetime of any system instance. On most kernels you can finesse this by adding static routes to 127.0.0.1 for each of your interface addresses, but some kernels don't like that trick and rather than give a detailed map of which ones work and which ones don't, I just globally recommend against 0.0.0.0. If you know enough to know that 127.0.0.1 or 0.0.0.0 is safe on your kernel and resolver, then feel free to use them. If you don't know for sure that it is safe, don't use them. I never use them (except on my laptop, whose hostname is "localhost" and whose 0.0.0.0 is 127.0.0.1 since I ifconfig my lo0 before any other interface). The operational advantage to using a real IP address rather than an wormhole like 0.0.0.0 or 127.0.0.1, is that you can then "rdist" or otherwise share identical copies of your resolv.conf on all the systems on any given subnet, not all of which will be servers.The problem was with older versions of the resolver (4.8.X). If you listed 127.0.0.1 as the first entry in resolv.conf, and for whatever reason the local name server wasn't running and the resolver fell back to the second name server listed, it would send queries to the name server with the source IP address set to 127.0.0.1 (as it was set when the resolver was trying to send to 127.0.0.1--you use the loopback address to send to the loopback address).
When you start having a very big domain that can be broken into logical and separate entities that can look after their own DNS information, you will probably want to do this. Maintain a central area for the things that everyone needs to see and delegate the authority for the other parts of the organization so that they can manage themselves.
Another essential piece of information is that every domain that exists must have it NS records associated with it. These NS records denote the name servers that are queried for information about that zone. For your zone to be recognized by the outside world, the server responsible for the zone above you must have created a NS record for your your new servers (NOTE that the new servers DO NOT have to be in the new domain). For example, putting the computer club onto the network and giving them control over their own part of the domain space we have the following.
The machine authorative for gu.uwa.edu.au is mackerel and the machine authorative for ucc.gu.uwa.edu.au is marlin.
in mackerel's data for gu.uwa.edu.au we have the following
@ IN SOA ...
IN A 130.95.100.3
IN MX mackerel.gu.uwa.edu.au.
IN MX uniwa.uwa.edu.au.
marlin IN A 130.95.100.4
ucc IN NS marlin.gu.uwa.edu.au.
IN NS mackerel.gu.uwa.edu.au.
Marlin is also given an IP in our domain as a convenience. If they
blow up their name serving there is less that can go wrong because
people can still see that machine which is a start. You could place
"marlin.ucc" in the first column and leave the machine
totally inside the ucc domain as well.
The second NS line is because mackerel will be acting as secondary name server for the ucc.gu domain. Do not include this line if you are not authorative for the information included in the sub-domain.
To delegate authority for PTR records, the same concepts apply.
stub 10.168.192.in-addr.arpa <subdomain server addr> db.192.168.10may be added to your primary server's named.boot in recent versions of bind. In other versions (and recent ones :-) ), the following lines may be added to the db.192.168.10 zone file to perform the same function:
xxx IN NS <server1> xxx IN NS <server2> xxx IN NS <server3> ; if needed ... xxx IN NS <serverN> ; if needed
Comments relating to running bind 4.9.x on a Sun OS 4.1.x system and the effect on sendmail, ftp, telnet and other TCP/IP services bypassing NIS and directly using named is documented quite well in the comp.sys.sun.admin FAQ in questions one and two. You can get them from:
ftp.ece.uc.edu : /pub/sun-faq/FAQs/sun-faq.general
There are others, but these are listed here:
ftp.inria.fr : /network/ipv6/
This is built into more recent versions of BIND (after 4.9.5?)
ftp.vix.com : /pub/bind/release/4.9.3/contrib/noforward.tar.gz
Also look at
ftp.is.co.za : /networking/ip/dns/bind/contrib/noforward.tar.gz
Mark Andrews has a patch that will tell a 4.9.4 server to listen to a particular interface and respond to DNS queries. It may be found at an unofficial location: http://www.ultra.net/~jzp/andrews.patch.txt
This is built into BIND 8.1.1.
Most name server implementations allow information about multiple domains to be kept on one server, and questions about those domains to be answered by that one server. For instance, there are many large servers on the Internet that each serve information about more than 1000 different domains.
To be completely accurate, a server contains information about zones, which are parts of domains that are kept as a single unit. [Ed note: for a definition of zones and domains, see Section 2: The Name Service in the "Name Server Operations Guide" included with the BIND 4.9.5 distribution.]
In the configuration of the name server, the additional zones need to be specified. An important consideration is whether a particular server is primary or secondary for any specific zone--a secondary server maintains only a copy of the zone, periodically refreshing its copy from another, specified, server. In BIND, to set up a server as a secondary server for the x.y.z zone, to the configuration file /etc/named.boot add the line
secondary x.y.z 10.0.0.1 db.x.y.z
where 10.0.0.1 is the IP address of the server that the zone will be
copied from, and db.x.y.z is a local filename that will contain the
copy of the zone.
If this is a question related to how to set up multiple IP numbers on one system, which you do not need to do to act as a domain server for multiple domains, see
http://www.thesphere.com/%7Edlp/TwoServers/.
Question 5.20. hostname and domain name the
same
Date: Wed Jul 9 21:47:36 EDT 1997
Q: I have a subdomain sub.foobar.com. I would like to name a host sub.foobar.com. It should also be the mail relay for all hosts in sub.foobar.com. How do I do this ?
A: You would add an A record for sub.foobar.com, and multiple MX records pointing to this host (sub.foobar.com). For example:
sub.foobar.com. IN A 1.2.3.4 ; address of host ; foo.sub.foobar.com. IN MX 10 sub.foobar.com. bar.sub.foobar.com. IN MX 10 sub.foobar.com. The host, sub.foobar.com, may also need to be to configured to understand that mail addressed to user@sub.foobar.com and possibly other sub.foobar.com hosts should be treated as local.
Q: How do I restrict my zone transfers to my secondaries or other trusted hosts?
A: Use the 'xfrnets' directive within the named.boot file or the 'secure_zone' TXT RR within a zone file. The BOG has more information on both of these options.
As an example within an 4.9.x named.boot file:
xfernets 10.1.2.0&255.255.255.0 44.66.10.0&255.255.255.0Only Nameservers on these networks will be able to do zone transfers from the server with this configuration.
Please note that 'secure_zone' restricts all access to the containing zone, as well as restricting zone transfers :-) .
BIND 8.x supports restricting zone transfers on a per-zone basis in the named.conf file, whereas BIND 4.9.x only supports xfrnets as a global option.
Chris Peckham - 16 July 1998