[plug] /newbie ..... nslookup

[Christian]

On Mon, May 22, 2000 at 10:38:13AM +0800, Earnshaw, Mike wrote:
> List,
> 
> When reviewing the logs I come across several access attempts that have been
> denied by the kernel on weird ports. I do an nslookup on the requesting IP
> and often get a message that the domain is non-existent. However when I ping
> the IP I get a response.

If there is no PTR record in the DNS for that address then you won't be
able to look it up.  Many ISPs don't bother with adding DNS records in
the in-addr.arpa domain for their address ranges and the result is that
you get a "domain non-existent" style message.  If you want to find out
information about the address then you could always try doing a
traceroute to it which will probably give you some idea of where the
machine is located.  You can also do searches in the whois database to
find out who the address range belongs to.

Regards,

Christian.