[ILUG] samba, nslookup and private network addresses.

[John N S Gill]

For a while now I've been chasing around trying to find out why our 
NT clients sometimes experience a long delay when first trying to 
connect to a samba share.

I think I have pinned the problem down to host name lookups.  
samba insists on doing these when a new host connects.  It looks up 
the hostname so it can check it against host allow/host deny info 
from the samba configuration file.   I had hoped I could stop samba 
from doing gethostbyaddr calls by using the "name resolve order"
appropriately.  But that only relates to how it should figure out 
Netbios names.  So at least for now I have to let it do its host 
lookups.

Meanwhile, I think the real problem may be down to the DNS servers 
themselves and/or the way I have things configured here.

The basic problem is I don't want to have to list all the clients in
/etc/hosts, so the result is any query to a host not listed goes to 
the nameserver.  Now we are not running our own nameserver, so the 
queries go out to our ISP.

It seems a bit dull to me to send queries for IP addresses on a 
private network out to an external nameserver, so it there any way to 
configure things so that these return straight away as unknown?  

Is the answer simply to run a nameserver locally?

Meanwhile, why do I get such varying results when I send queries 
relating to private network addresses to my favourite nameservers?
Sometimes I get an instant Non-existent host/domain response, other 
times I get a 15 second wait and a time out.

Eg:

jng> time nslookup  172.17.1.111 192.111.39.1
Server:  ns.isi.ie
Address:  192.111.39.1

*** ns.isi.ie can't find 172.17.1.111: Non-existent host/domain
0.01user 0.00system 0:00.08elapsed 11%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (118major+22minor)pagefaults 0swaps

jng> time nslookup  172.17.1.112 192.111.39.1
Server:  ns.isi.ie
Address:  192.111.39.1

*** ns.isi.ie can't find 172.17.1.112: No response from server
0.00user 0.00system 0:15.04elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (118major+22minor)pagefaults 0swaps

John