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DNS problem
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DNS problem



hi, all,

As mentioned on this list, many problems may relate to DNS, so I wanted to verify that my DNS setup is ok.

> hermes:~ admin$ host hermes.gymherm.net
> hermes.gymherm.net has address 172.16.0.1
>
> hermes:~ admin$ host 172.16.0.1
> 1.0.16.172.in-addr.arpa domain name pointer hermes.gymherm.net.

This is how I would like the whole system to behave.

dscacheutil -q host -a name hermes.gymherm.net
dscacheutil -q host -a ip_address 172.16.0.1

both return the same, even on our clients: ok.

However, nslookup returns differently:

> hermes:~ admin$ nslookup hermes.gymherm.net
> Server:		192.168.0.101
> Address:	192.168.0.101#53
>
> Name:	hermes.gymherm.net
> Address: 172.16.0.1


I also tried dig:

> hermes:~ admin$ dig hermes.gymherm.net
>
> ; <<>> DiG 9.6.0-APPLE-P2 <<>> hermes.gymherm.net
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 41260
> ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0
>
> ;; QUESTION SECTION:
> ;hermes.gymherm.net.		IN	A
>
> ;; ANSWER SECTION:
> hermes.gymherm.net.	10800	IN	A	172.16.0.1
>
> ;; AUTHORITY SECTION:
> gymherm.net.		10800	IN	NS	hermes.gymherm.net.
>
> ;; Query time: 0 msec
> ;; SERVER: 192.168.0.101#53(192.168.0.101)
> ;; WHEN: Sun Mar 27 12:20:11 2011
> ;; MSG SIZE  rcvd: 66


from

> http://www.fischerlaender.net/it-stuff/mac-os-x-clear-dns-cache-and-the-dig-utility

I learned that dig uses /etc/resolv.conf

> hermes:~ admin$ more /etc/resolv.conf
> #
> # Mac OS X Notice
> #
> # This file is not used by the host name and address resolution
> # or the DNS query routing mechanisms used by most processes on
> # this Mac OS X system.
> #
> # This file is automatically generated.
> #
> nameserver 192.168.0.101


The comment in this file confuses me. Now I am trying to find out, where that 192.168.0.101 entry comes from. A screenshot from Server Admin/DNS can be found here.[1]

To understand where this mess comes from: the machine has two NICs:

en1 provides services to 172.16.*.* and does nat/routing via
en0 to a dsl-modem in 192.168.*.*

In the original setup on our old machine under 10.4 server, DNS was set up to resolve both 172.16.0.1 and 192.168.0.100 to hermes.gymherm.net. When I took over this machine, I never changed or questioned this setting. Later, we got an Intel XServe and I needed to migrate to 10.5 and wanted to keep the Intel XServe alongside the old machine, so the new machine got 192.168.0.101 in the external net. By now, I have migrated the new machine to 10.6.6. On this occasion I recognised that our server returned:

> hermes:~ admin$ sudo changeip -checkhostname
> Password:
>
> Primary address     = 192.168.0.101
>
> Current HostName    = hermes.gymherm.net
> DNS HostName        = hermes.gymherm.net
>
> The names match. There is nothing to change


I do not know, if this problem existed before, is a result of the migration or a setup problem that was caused after the migration.

So I tried to find out, why it does not use 172.16.0.1. As I could not manage to fix this, I deleted the - as I think, please correct me - unnecessary entry for the external net. But as you might have guessed, it now returns:

> hermes:~ admin$ sudo changeip -checkhostname
> Password:
>
> Primary address     = 192.168.0.101
>
> Current HostName    = hermes.gymherm.net
>
> The DNS hostname is not available, please repair DNS and re-run this tool.
>
> dirserv:success = "success"

As you can see in [1] there is no mention of this ip-address in my DNS setup. reboot and dscacheutil -flushcache do not change this state.

I reverted to the old settings, where hermes.gymherm.net resolves to both addresses and changeip now returns ok again. But only because it uses the 192.16.0.101 address, I would like it to use 172.16.0.1.[2]

Any directions to a remedy are very welcome, TIA,

Michael.

[1] http://www.virtosphere.de/data/tmp/ssp_temp_capture.png
[2] we observe long delays on accepting print jobs and sometimes failed logins, I was hoping these problems were related to this DNS issue.







--
Gymnasium Hermeskeil                  Schwerpunkte Musik und Informatik
Borwiesenstrasse 19-21                            http://www.gymherm.de
54411 Hermeskeil                            Fon / Fax: 01803-5518-64241







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