Ping and nslookup return different ip
Joe
When I ping the FQDN for our mail server the ip address
returned is the outside (NAT) ip. If I ping the netbios
name the internal ip is returned. Nslookup against the
internal DNS server returns the internal ip. This is only
for one server. Nslookup and ping return the internal ip
for all other hosts.
I have deleted and recreated the host record for the
server in question. I am considering rebuilding the DNS
server but since nslookup returns the correct ip I doubt
that would correct the problem.
Help!!!
Joe
Konstantinos Kostis
<news:332d01c15e35$8e098230$9ae62ecf@tkmsftngxa02...>
> Winnt 4.0 SP6
> When I ping the FQDN for our mail server the ip address
> returned is the outside (NAT) ip. If I ping the netbios
> name the internal ip is returned.
Is there anything wrong with this? ping will most likely
resolve the name using WINS (or local broadcasts - depends
on your configuration).
> Nslookup against the internal DNS server returns
> the internal ip.
Did you nslookup just the hostname or the FQDN?
> This is only for one server.
How many other servers have NATed outside addresses?
If it's only this one, shouldn't this be expected?
> Nslookup and ping return the internal ip for all
> other hosts.
What's your internal DNS domain name? What your
domain search suffix? Identical or different from
your outside FQDN?
> I have deleted and recreated the host record for the
> server in question. I am considering rebuilding the DNS
> server but since nslookup returns the correct ip I doubt
> that would correct the problem.
Don't. I have the same doubts. ;)
John R Buchan
provided enough detail on that to allow any further analysis.
Ping, like most winsock apps will resolve names in the following order:
Local machine (is it resolving its own name)
hosts
DNS
NetBIOS cache
WINS
broadcast
lmhosts
Note. This assumes h-node. Other node types can alter the order or
presence of the NetBIOS methods.
When attempting to resolve a host name (or computer name) only (not DNS
domain provided), a DNS client will append its own DNS domain to the
host name, before passing it to the DNS server. If the client has DNS
domains specified in its Domain Name Suffix Search Order list, it will
also try each of those domains. It sounds like none of the combinations
the client is able to attempt can be resolved via the external DNS. So
the client falls through to NetBIOS methods and ends up with the
server's internal IP.
When attempting to resolve a FQDN, the client will pass that value
directly to the DNS server. You are apparently providing an FQDN that is
resolvable via the external DNS servers. This results in the FQDN being
resolved to the external IP.
Unless you are hosting your own external DNS server it is extremely
unlikely you will ever be able to have the external DNS server resolve
your server's name to it's internal IP. If this did happen, it would
cause connectivity problems for any external machines attempting to
reach the server, since they would be unable to reach (or probably even
route to) its internal IP.
I can think of 2 obvious solutions to your problem:
1) Implement your own internal DNS server that passes unresolved
queries along to the external DNS and provide the internal DNS server
with an entry to resolve your server's FQDN to its internal IP.
2) Give each of your machines a hosts file with the server's FQDN
mapped to its internal IP.
On Fri, 26 Oct 2001 08:46:30 -0700, "Joe" <esca...@hooks.esc8.net>
wrote:
--
Note, I seldom respond to email questions. Please keep discussions in
the news group, so everyone can benefit from them (including me <g>).
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John R Buchan Orlando, Florida USA
MCSE -++- MVP ...................... jrb-tech(at)unknownegg(dot)org