dns resolution: nslookup/other command

[Vi.]

Hi,

I have a problem with dns resolution.
The dns resolution works fins with nslookup but doesn't work with the
other bash commands (such as ping).

# nslookup host.domain.com
server: ns
address: 192.168.1.2

name: host.domain.com
address: 192.168.1.10

So nslookup works but:

# ping host.domain.com
ping: unknown host host.domain.com

Any idea ?

Thanks

Vi.

[Barry Margolin]

Is this a Solaris system? Make sure you have "dns" in the "hosts" line of
/etc/nsswitch.conf.

--
Barry Margolin, bar...@genuity.net
Genuity, Burlington, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.

[Vi.]

>Is this a Solaris system? Make sure you have "dns" in the "hosts" line of
>/etc/nsswitch.conf.
>

Yes, this is on Solaris but there is already the correct entry in nsswitch.conf:
hosts: files dns

The DNS query is sent by the client, a correct answer is replied by the
DNS server but the client replies by a "ICMP Destination unreachable"
From snoop:
172.16.56.4 -> lithium DNS C oxygen.domain.com. Internet Addr ?lithium ->
172.16.56.4 DNS R oxygen.domain.com. Internet Addr 172.16.48.16
172.16.56.4 -> lithium ICMP Destination unreachable (UDP port 33228
unreachable)

Thanks.

Vi.

[G. Roderick Singleton]

Off hand I'd guess you have a routing problem or a firewall getting in
the way. e.g. packet goes out, answer comes back, packet doesn't get
to target.
--
________________________________________________________________________________
G. Roderick Singleton, <gsing...@home.com>
________________________________________________________________________________

"We of the West add degree upon degree, as stucco troweled on chicken
netting tacked to shoddy wooden framing. Real education ... it is not
the laying of one layer, it is the opposite, it is attrition, peeling
away, wearing away superfluities, as an artist in jade wears away the
rubbish, untul the goddess, the flower, the stallion from the beginning
in the heart of the jade is revealed. Education is not adding. It is
scraping away garbage, trash, revealing hidden realiity." E. Hoffman
Price

[Barry Margolin]

In article <9i7imk$l...@pub3.rc.vix.com>,

G. Roderick Singleton <gsing...@home.com> wrote:
>> The DNS query is sent by the client, a correct answer is replied by the
>> DNS server but the client replies by a "ICMP Destination unreachable"
>> From snoop:
>> 172.16.56.4 -> lithium DNS C oxygen.domain.com. Internet Addr ?lithium ->
>> 172.16.56.4 DNS R oxygen.domain.com. Internet Addr 172.16.48.16
>> 172.16.56.4 -> lithium ICMP Destination unreachable (UDP port 33228
>> unreachable)
>>
>> Thanks.
>>
>> Vi.
>
>Off hand I'd guess you have a routing problem or a firewall getting in
>the way. e.g. packet goes out, answer comes back, packet doesn't get
>to target.

That's not what snoop says. It shows the packet being received by the
client and the client sending an ICMP error when that happens. Also notice
that it's a *port* unreachable error, not a host unreachable.

This can happen if the server takes too long to reply to the query. If the
client has timed out, it will no longer be listening on the port that the
answer is going to, so a Port Unreachable error will result.

[G. Roderick Singleton]

Barry Margolin wrote:
>
> In article <9i7imk$l...@pub3.rc.vix.com>,
> G. Roderick Singleton <gsing...@home.com> wrote:
> >> The DNS query is sent by the client, a correct answer is replied by the
> >> DNS server but the client replies by a "ICMP Destination unreachable"
> >> From snoop:
> >> 172.16.56.4 -> lithium DNS C oxygen.domain.com. Internet Addr ?lithium ->
> >> 172.16.56.4 DNS R oxygen.domain.com. Internet Addr 172.16.48.16
> >> 172.16.56.4 -> lithium ICMP Destination unreachable (UDP port 33228
> >> unreachable)
> >>
> >> Thanks.
> >>
> >> Vi.
> >
> >Off hand I'd guess you have a routing problem or a firewall getting in
> >the way. e.g. packet goes out, answer comes back, packet doesn't get
> >to target.
>
> That's not what snoop says. It shows the packet being received by the
> client and the client sending an ICMP error when that happens. Also notice
> that it's a *port* unreachable error, not a host unreachable.
>
> This can happen if the server takes too long to reply to the query. If the
> client has timed out, it will no longer be listening on the port that the
> answer is going to, so a Port Unreachable error will result.
>

Why thanks. I was only trying to help the poor fellow and don't really
care.

Were I the admin of that system. I certainly would have paid more
attention to the error message and fixed it.

I still hold that had this fellow followed his packets in and out he
would have caught problem.