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vincenzo romero

2008-Mar-21 00:26 UTC

[CentOS] simple DNS question - reverse nslookup fails.

Hello all,

I am trying to configure a subdomain DNS server on a Cent OS 5.1 - for
my lab.  Brief configuration:

Lab machine ---> 192.168.17.2 (should respond to DNS queries from
hosts in 192.168.16.0/20 network)

1.  I would also like to forward any queries outside the above network
to our corporate domain (no firewalls between our 192.168.16.x network
and the corporate network.  The domain server is:  dns.company.com
with an IP of 10.100.1.2 (255.255.255.0).

2.  What I have configured is:

192.168.17.2 --> myhost.lab.company.com
10.100.1.2 -->  dns.company.com

3.  Installed the dns bind 9 in myhost and set basic configuration via
the system-config-bind GUI.  My configuration file specific to my
setup there is:

 cat lab.maxiscale.com.db
$TTL 1H
@       SOA     myhost.lab.company.com.
root.myhost.lab.company.com. (       2
                                                3H
                                                1H
                                                1W
                                                1H )
        NS      myhost.lab.company.com.
qaserver2 A       192.168.17.3
qaserver1 A       192.168.17.1
myhost A       192.168.17.2

================
The rest of the DNS/Bind records were based upon the auto-generated
files from the Bind GUI Config tool.

3.  I also changed myhost's resolv.conf to reflect the following:

search lab.mycompany.com
192.168.17.2
search mycompany.com
10.100.1.2

=====
PROBLEM:

1.  When I am in myhost.com, I can perform:
a.  nslookup hostname (to any host within 192.168.x and 10.100.x networks)
b.  nslookup ip to anyhost wtihin both networks.

2.  When I am in one of the hosts within 192.168.x aside from
myhost.com (for example, qaserver1 or qaserver2):

a: SUCCESS to nslookup hostname to any host within BOTH networks.
b.  FAILS to nslookup ip (reverse nslookup) to anyhost within the
10.100.x network.

this is the error I get:

nslookup 10.100.1.2
Server:         192.168.17.2
Address:        192.168.17.2#53

Non-authoritative answer:
24.1.100.10.in-addr.arpa        name = dns.company.com.

Authoritative answers can be found from:
.       nameserver = e.root-servers.net.
.       nameserver = f.root-servers.net.
.       nameserver = g.root-servers.net.
.       nameserver = h.root-servers.net.
.       nameserver = i.root-servers.net.
.       nameserver = j.root-servers.net.
.       nameserver = k.root-servers.net.
.       nameserver = l.root-servers.net.
.       nameserver = m.root-servers.net.
.       nameserver = a.root-servers.net.
.       nameserver = b.root-servers.net.
.       nameserver = c.root-servers.net.
.       nameserver = d.root-servers.net.
a.root-servers.net      internet address = 198.41.0.4
b.root-servers.net      internet address = 192.228.79.201
c.root-servers.net      internet address = 192.33.4.12
d.root-servers.net      internet address = 128.8.10.90
e.root-servers.net      internet address = 192.203.230.10
f.root-servers.net      internet address = 192.5.5.241
g.root-servers.net      internet address = 192.112.36.4
h.root-servers.net      internet address = 128.63.2.53
i.root-servers.net      internet address = 192.36.148.17
j.root-servers.net      internet address = 192.58.128.30
k.root-servers.net      internet address = 193.0.14.129
k.root-servers.net      has AAAA address 2001:7fd::1
l.root-servers.net      internet address = 199.7.83.42

====
I must be missing something stupid and apparent .... any help would be
greatly appreciated!!!

:)

thanks in advance!


-- 
best,

Vince

mouss

2008-Mar-21 19:59 UTC

head link

[CentOS] simple DNS question - reverse nslookup fails.

vincenzo romero wrote:> Hello all,
>
> I am trying to configure a subdomain DNS server on a Cent OS 5.1 - for
> my lab.  Brief configuration:
>
> Lab machine ---> 192.168.17.2 (should respond to DNS queries from
> hosts in 192.168.16.0/20 network)
>
> 1.  I would also like to forward any queries outside the above network
> to our corporate domain (no firewalls between our 192.168.16.x network
> and the corporate network.  The domain server is:  dns.company.com
> with an IP of 10.100.1.2 (255.255.255.0).
>
> 2.  What I have configured is:
>
> 192.168.17.2 --> myhost.lab.company.com
> 10.100.1.2 -->  dns.company.com
>
> 3.  Installed the dns bind 9 in myhost and set basic configuration via
> the system-config-bind GUI.  My configuration file specific to my
> setup there is:
>
>  cat lab.maxiscale.com.db
> $TTL 1H
> @       SOA     myhost.lab.company.com.
> root.myhost.lab.company.com. (       2
>                                                 3H
>                                                 1H
>                                                 1W
>                                                 1H )
>         NS      myhost.lab.company.com.
> qaserver2 A       192.168.17.3
> qaserver1 A       192.168.17.1
> myhost A       192.168.17.2
>
> ================>
> The rest of the DNS/Bind records were based upon the auto-generated
> files from the Bind GUI Config tool.
>
> 3.  I also changed myhost's resolv.conf to reflect the following:
>
> search lab.mycompany.com
> 192.168.17.2
> search mycompany.com
> 10.100.1.2
>   what's this?  should be:

search lab.mycompany.com mycompany.com
server 192.168.17.2
server 10.100.1.2> =====>
> PROBLEM:
>
> 1.  When I am in myhost.com, I can perform:
> a.  nslookup hostname (to any host within 192.168.x and 10.100.x networks)
> b.  nslookup ip to anyhost wtihin both networks.
>
> 2.  When I am in one of the hosts within 192.168.x aside from
> myhost.com (for example, qaserver1 or qaserver2):
>
> a: SUCCESS to nslookup hostname to any host within BOTH networks.
> b.  FAILS to nslookup ip (reverse nslookup) to anyhost within the
> 10.100.x network.
>   
you did not create the reverse zone. the zone file should contains 
something like

$TTL 1H
@       SOA     myhost.lab.company.com.
root.myhost.lab.company.com. (       2
                                                3H
                                                1H
                                                1W
                                                1H )
        NS      myhost.lab.company.com.


3              IN      PTR     qaserver2.lab.company.com.
1              IN      PTR     qaserver2.lab.company.com.
2              IN      PTR     myhostA.lab.company.com.

WARNING. don't forget the trailing dot (...lab.company.com. with a dot 
at the end).

you must tell you bind that it is authoritative for this zone. so in 
named.conf, add


zone "17.168.192.IN-ADDR.ARPA" {
        type master;
        file "192.168.17.db";
};

where 192.168.17.db is the name of the zone file.

A good reference for DNS is
    http://www.zytrax.com/books/dns/

Robert Moskowitz

2008-Mar-24 20:17 UTC

head link

[CentOS] simple DNS question - reverse nslookup fails.

vincenzo romero wrote:>>  where 192.168.17.db is the name of the zone file.
>>
>>  A good reference for DNS is
>>     http://www.zytrax.com/books/dns/
>>     
>
> thank you for the reference and response... I have also checked the
> above and reviewed it.... and attempted to follow the configuration
> file samples;  however I noticed in CentOS is that I either:
>
> - use the Bind Configuration Tool
> or
> - configure DNS manually (byhand, hence the above reference should be
followed).
>
> As I am a newbie, I attempted to configure using the Bind
> Configuration Tool (GUI) that automatically creates my records files;
> The questions I have are:
>   Use webmin. (webmin.com). I am an old hand at BIND and use webmin 
regularly....> 1.  Is there some URL or reference that has a "step-by-step-DNS
> configuration" based upon the Bind configuration Tool (GUI)?  the
> manuals is not a cookbook and could potentially cause newbies to make
> mistakes.  the HOW-TO-FORGE document - does NOT show step-by-step but
> only shows how to INSTALL bind.  ... If anyone is aware of such a
> link, I would appreciate pointers to where.
>
> 2.  I did not seem to find a place to configure my /etc/resolv.conf -
> do I configure this from the Network Manager?  Again, I feel that I
> should configure all via GUI since it seems that if I configure
> sometimes by editing files or by GUI, then the configuration gets
> messed up.
>
> thanks in advance,
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
>
>

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