help with unwanted reverse DNS's please???
Kevin Darcy
kcd at daimlerchrysler.com
Thu Apr 5 19:58:00 UTC 2001
If you're using an /etc/hosts file to reverse-resolve the addresses, then
this has nothing to do with DNS.
Are you actually getting connections from the 192.168.*.* addresses, or
from NAT'ed addresses? In either case, you need to ensure that whatever
resolution mechanism (DNS, /etc/hosts file) you're using to
reverse-resolve those addresses to names, knows about the source
addresses from which you're getting connections. My guess is that you're
getting connections from NAT'ed addresses that aren't in your /etc/hosts
file, so they're being looked up in DNS and getting resolved from your
ISP's nameservers.
-Kevin
bobm at financialdatacorp.com wrote:
> I don't know if this would be the right forum but it does involve
> TCPIP so here goes...
>
> We have an internal LAN with a unix(AIX) server and all Win98SE
> clients. The clients all telnet into our server to access our main
> application(s). The server identifies each connecting device by the
> identity delivered by telnet. The application then sees the IP
> address or the host name. All of our internal IP's are private in
> the range of 192.168.0.xxx which has/was working perfectly for quite
> some time.
>
> Recently we changed our ISP to another provider through a T1 link.
> The router is connected to the LAN and has its own internal IP
> address. It also has NAT configured to allow any/all of the internal
> clients to gain access to the Internet. This also works well.
>
> And, on these clients we have the ISP's DNS servers definded as we do
> not do our own DNS.
>
> So, here's the problem:
>
> Since the day of installation of the new ISP, our users are not being
> identified correctly when telnetting into our application server.
> What is being seen by the server is a qualified hostname which is
> actually the hostname of the ISP's INTERNAL network for the client
> with the SAME INTERNAL IP address.
>
> Example:
>
> We have a typical user whose Win98SE machine has an IP of 192.168.0.39
> and the Win98 Identification is PC39. On our application server we
> also have an /etc/hosts file with an appropriate entry. Previously we
> would see the IP as the identification for this client when
> establishing a session.
>
> Now we see a host name only which is that of the internal client of
> the ISP whose internal IP address is the same (192.168.0.39). The ISP
> says there's nothing that they can do about this!
>
> We had a prior ISP with NAT and we had no problem whatsoever.
>
> QUESTIONS:
>
> 1) The router is a CISCO 2524/2624 so is there anything in the router
> config to prevent reverse DNS? To prevent reversing internal IP's?
>
> 2) Anything the ISP or we can/could do to rectify this situation?
>
> I am at a loss.
>
> Thank you.
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