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Old 03-26-2007, 08:06 PM   #1
loopy69
LQ Newbie
 
Registered: Apr 2004
Distribution: Fedora Core 5
Posts: 23

Rep: Reputation: 15
DNS Server: WinXP DNS clients losing name resolution frequently


Hi,

I am experiencing the loss of name resolutions periodically with my WinXP clients.

Our mail server (running scalix) relies on resolving our mailserver hostname 'mailserv' at the client in order to make a mail connection. Every so often (1-2 days) a few random clients lose their resolution and can't connect to 'mailserv' with outlook. I usually release the dhcp address with ipconfig /release and then renew with ipconfig /renew and then the resolution appears to be working again.

I also run samba on a different server as a WINS server (which I needed to get resolution to the samba server before I had setup the DNS server). Is running these two services in conjunction causing this loss of DNS resolution? Is there a way for me to troubleshoot how the problem is occurring?

Both servers are running Fedora Core 5 with lastest updates.

Any help is greatly appreciated.

Thanks,
Brett
 
Old 03-27-2007, 01:50 PM   #2
JimBass
Senior Member
 
Registered: Oct 2003
Location: New York City
Distribution: Debian Sid 2.6.32
Posts: 2,100

Rep: Reputation: 48
WINS and DNS are similar but far from identical. I would NOT run both. How do you know if the problem is WINS or DNS?

All you mention is a problem resolving 'mailserv'. That is a single name, so it appears to be a WINS address, unless you just used that as an abbreviation here, when Outlook is actually asking for mailserv.domain.local or whatever?

Please provide more details if possible. Also, on a test machine, try replacing the 'mailserv' address with the actual IP address of the mailserv, and see if that causes the resolution to work better, in that case because there is no resolution being done.

Peace,
JimBass
 
Old 03-27-2007, 07:21 PM   #3
loopy69
LQ Newbie
 
Registered: Apr 2004
Distribution: Fedora Core 5
Posts: 23

Original Poster
Rep: Reputation: 15
Hi Jim,

Thanks for the response. I agree I don't know if the problem is WINS or DNS but I think that the name 'mailserv' or 'mailserv.iii.net.au' is only registered with our DNS server. I also know that I have another CNAME record which people use in the office regularly which fails DNS resolution, this is 'www.iii.net.au' which is our external website so internally I map that name to the correct internal ip address (see the zones below).

I'll digress to explain my situation as much as possible.

We run two linux servers on fedora core 5 respectively named fileserv and mailserv.

Fileserv runs samba (3.0.23) as a primary domain controller for the domain 'IIIUNANDERRA'. We use an LDAP backend with openldap to store the login configuration and our file sharing services are all on this machine. Mailserv runs our mail software which is a combination of sendmail, mailscanner, spamassassin + plugins and scalix. This mailserv machine is also our webserver (apache) and dns server.

I've found it a little confusing as to whether I actually can disable WINS when running samba as a PDC as DNS does not provide all of the necessary name resolution for a domain. Here is an old post but I think it explains a fair bit about the subject, alas samba cannot yet replace a full active directory domain so WINS is still required; http://lists.samba.org/archive/samba...er/112954.html

So at the moment I am running both services and my DNS server config includes these two zones;
Forward lookup zone called 'iii.net.au'

[root@mailserv named]# cat iii.net.au.zone
$TTL 3M

iii.net.au. IN SOA mailserv.iii.net.au bcarruthers.iii.net.au. (
2007032002 ; serial
2H ; refresh slaves
5M ; retry
1W ; expire
1M ; Negative TTL
)

@ IN NS 192.168.0.9
mailserv.iii.net.au. IN A 192.168.0.9 ; Mail/DNS/Web server
fileserv.iii.net.au. IN A 192.168.0.8 ; Samba/LDAP file server
firewall.iii.net.au. IN A 192.168.0.1 ; Cisco PIX firewall
wireless1.iii.net.au. IN A 192.168.0.4 ; Upstairs wireless
optserv.iii.net.au IN A 192.168.0.151 ; Optrix server
www IN CNAME mailserv ; Internal mapping for webserver
#mailserv IN CNAME mailserv.iii.net.au. ; Alias for mailserv
#webserv IN CNAME webserv.iii.net.au. ; Alias for webserv

@ IN MX 10 mailserv.iii.net.au.

Reverse zone 192.168.0.zone
[root@mailserv named]# cat 192.168.0.zone
$TTL 3M

@ IN SOA mailserv.iii.net.au bcarruthers. (
2007032002 ; serial
2H ; refresh slaves
5M ; retry
1W ; expire
1M ; Negative TTL
)

IN NS mailserv.iii.net.au.
1 IN PTR firewall.iii.net.au.
4 IN PTR wireless1.iii.net.au.
8 IN PTR fileserv.iii.net.au.
9 IN PTR mailserv.iii.net.au.
#9 IN PTR www.iii.net.au.
11 IN PTR webserv.iii.net.au.
151 IN PTR optserv.iii.net.au.

The conditions when I say resolution is not working refers to the following conditions;
When I try to ping mailserv i timeout
When I try to nslookup mailserv it works

Would this mean its the wins resolution serving the ping command? I'm sure nslookup is DNS. Is there a way to change the name resolution order on the clients to use DNS and then WINS?

I hope I've given you more information and sorry if I am confusing in any way.

Many thanks,
Brett
 
Old 03-27-2007, 07:25 PM   #4
loopy69
LQ Newbie
 
Registered: Apr 2004
Distribution: Fedora Core 5
Posts: 23

Original Poster
Rep: Reputation: 15
Client settings

Also, here is a client connections dhcp assigned settings

Ethernet adapter Wireless Network Connection:

Connection-specific DNS Suffix . : iii.net.au
Description . . . . . . . . . . . : Intel(R) PRO/Wireless 3945ABG Networ
k Connection
Physical Address. . . . . . . . . : 00-13-02-0C-4A-D6
Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.0.52
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.0.1
DHCP Server . . . . . . . . . . . : 192.168.0.1
DNS Servers . . . . . . . . . . . : 192.168.0.9
203.12.160.35
Primary WINS Server . . . . . . . : 192.168.0.8
Secondary WINS Server . . . . . . : 192.168.0.9
Lease Obtained. . . . . . . . . . : Wednesday, 28 March 2007 9:07:35 AM
Lease Expires . . . . . . . . . . : Wednesday, 28 March 2007 10:07:35 AM

The secondary WINS server address is indeed wrong here...

Cheers
 
Old 03-27-2007, 10:21 PM   #5
JimBass
Senior Member
 
Registered: Oct 2003
Location: New York City
Distribution: Debian Sid 2.6.32
Posts: 2,100

Rep: Reputation: 48
A few problems exist in the zone file, which should be easily correctable -

Quote:
I also know that I have another CNAME record which people use in the office regularly which fails DNS resolution, this is 'www.iii.net.au' which is our external website so internally I map that name to the correct internal ip address (see the zones below).

www IN CNAME mailserv ; Internal mapping for webserver
#mailserv IN CNAME mailserv.iii.net.au. ; Alias for mailserv
#webserv IN CNAME webserv.iii.net.au. ; Alias for webserv
You map www via a CNAME to mailserv, then comment out the mailserv entry. So www.iii.net.au maps to nothing. You should either uncomment the mailserv line, or change the CNAME to the full address of mailserv.iii.net.au.

In regards to the mailserv entry, I don't know jack about WINS, and no offense is intended, but I don't plan on learning it. It would seem to me that somehow you should be able to specify what lookup method windows uses first, DNS or WINS. That of course is what I would call the logical thing, so it is possible windows doesn't give you that choice. If nslookup of the single name, mailserv works, then either -

a) you have the DNS settings on the clients set to automatically append the domain name to a lookup, so when you type "ping mailserv", what actually gets asked is "ping mailserv.iii.net.au".
b) it isn't asking the DNS, but rather the WINS.

I would (if you are able to institute this level of change) set up DHCP from one of the linux boxes (is it doing that already?) and set the DHCP box to update the forward and reverse zones of the DNS by the rndc utility. The nice thing about that is it allows you to get full resolution of host names (like mailserv) from the DNS, which I would think is much better documented than WINS, but could be wrong. Again, I don't do domains at all at work or home, but I have set up this DHCP/DDNS combo and had it work within domains in the recent past.

Peace,
JimBass
 
  


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