Reverse lookup failure

I just recently changed from cable modem to DSL with a local ISP.

The setup in the house is Smoothwall running on a computer accessing the
Internet through broadband service provider. The machine is setup to allow
secure shell into the house so I can get files off of my computer that I may
need. It also is setup to look to the DSL modem for DNS answers.

Network in the house is switched through an eight port Linksys 10/100 switch
with a mix of linux machines and one windows 2000 machine.

What I am seeing on occasion is that a sight will be unreachable because the
address that is returned from DNS is not a valid address.

As an example, this morning I was reading www.cnn.com and had read several
articles. I clicked back on the mozilla browser that I use and nothing
happened. I immediately pinged www.cnn.com and got an address of 1.0.0.0
as the DNS resolution. This has happened with other sites also. One that
comes to mind is www.qwest.com. At the time that this is happening I can
go to other sites and see them. But if there is a site that I can't get to
it will respond to the ping with an address of 1.0.0.0. When those sites
are working I get a correct address back from the site. btw cnn.com does
not actually respond to the ping but I do get a DNS resolution from them.

When I tried to ping from the maintenance page of Smoothwall it indicated a
reverse DNS lookup failure.

My ISP doesn't have a clue as to what is going on and I have not had a
chance to run the dig command from a command line when any of this is not
working properly. I just found out about dig this afternoon at work and
plan on using it as soon as possible. Another thing that I found out about
is www.dnsstuff.com that will check into dns information from their site.

I have googled the problem with multiple different combinations of words and
nothing comes back yet. I will continue to google and look for answers but
I am hopeful that someone here might know what all this means.



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Hello,

On Fri, 16 Sep 2005 00:02:49 -0500, Allan Butler wrote:

> I immediately pinged www.cnn.com and got an address of 1.0.0.0

Are you using DHCP? Do you have static IPs?
If Y and N, then have you changed/added any other kit to your network?
Routers and even printservers have been known to mess with DNS.

> It also is setup to look to the DSL modem for DNS answers.

Surely, it looks to your ISP's nameservers for DNS.
cat /etc/resolv.conf

> I just found out about dig this afternoon at work and plan on using it
> as soon as possible.

Also see ifconfig, host and traceroute. (And man

HTH

--tim

Tim Lingard wrote:

> Hello,
>
> On Fri, 16 Sep 2005 00:02:49 -0500, Allan Butler wrote:
>
>> I immediately pinged www.cnn.com and got an address of 1.0.0.0
>
> Are you using DHCP? Do you have static IPs?
> If Y and N, then have you changed/added any other kit to your network?
> Routers and even printservers have been known to mess with DNS.

Everything on the network is the same as it was with Cable modem. The
answers by the way are yes and no.

>
>> It also is setup to look to the DSL modem for DNS answers.
>
> Surely, it looks to your ISP's nameservers for DNS.
> cat /etc/resolv.conf

The DSL modem is looking where ever it is told to look for DNS when it pulls
it's IP address from the DHCP server that feeds it from my ISP.

>
>> I just found out about dig this afternoon at work and plan on using it
>> as soon as possible.

I had another instance of this happening this afternoon. The results from
dig showed that the dns server in the dsl modem is the source of the bad
address. I don't know what is causing it yet but I will look in the modem
to see what I can see it is using in it's kernel. It is after all a small
linux kernel and OS mounted in proprietary hardware.

>
> Also see ifconfig, host and traceroute. (And man
>
> HTH
>
> --tim


Yes Tim. I do know how to use man and look at the different utilities that
are used in IP networking with Linux. I had done a traceroute and with the
IP address of 1.0.0.0 it is not showing anything valid as there is no known
route to that address.

I plan on doing some more investigation with the website at
www.dnsstuff.com . It is very good at getting information about a lot
of different addresses.

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I have DSL and a router, and I recently had a week-long go around with a
single web site I could not reach. It was driving me crazy. I had a
shell account and several home pages at that site, and it was the only
site in the universe I coldn't reach. I couldn't ping them, ftp,
telnet, pop e-mail, nothin'. Yet everything looked just fine from my
other computer which was fed through the same router, so I didn't
realize my router was the problem. Of course the sys-admin of that
system was stumped. He suggested I reformat my hard drive (gak!).

But you know what fixed it? Taking the router out of the pathway and
plugging the DSL directly into the computer that had the problem. That
fixed it! So then I powered off the router (simply resetting had not
helped), powered it back on, and fed the DSL back through the router.

It's been fine ever since.

And no, in this event I found that CNN doesn't answer pings, but some
other big names do. :-)

Good luck,

Suzanne.

Allan Butler wrote:

> As an example, this morning I was reading www.cnn.com and had read several
> articles. I clicked back on the mozilla browser that I use and nothing
> happened. I immediately pinged www.cnn.com and got an address of 1.0.0.0
> as the DNS resolution.

PS --- my problems began when I was opening multiple simultaneous
bookmarked tabs in Mozilla, and navigating around, likely with lots of
forward and back button use. (I tend to do that.)

I suspect there is a hiccup in Mozilla that somehow confounds your DNS
and router configurations if you jump around too quickly. Maybe it's a
bug. I don't know if it's been reportped.

Suzanne.

Suzanne. wrote:

> I suspect there is a hiccup in Mozilla that somehow confounds your DNS
> and router configurations if you jump around too quickly. Maybe it's a
> bug. I don't know if it's been reportped.

I take it back --- typing the IP address directly into the browser
address bar still didn't help in my case, so the DNS couldn't have been
messed up. See if you can reach the web sites in question by typing
their IP addresses directly into the browser. If that doesn't work
disconnect/reconnect your router.

Hope that helps, and I'll shut up now :-)

Suzanne.

Thanks Suzanne;

Everything that I have seen so far is pointing at the firmware inside the
DSL modem. It will work fine for a while and then it will start sending
back the 1.0.0.0 address for pages that it was just at a few seconds ago.
Some of these sites were cnn and google and yahoo, along with one or two
my wife went to.

I have changed the DNS machines that my firewall looks for and the DNS that
my desktop machine use. They are no longer looking to the modem for DNS
resolution. They are now looking for particular DNS machines on the network
and in the short time I have had them doing that there have been no more
problems.

I may point my personal machine at the same DNS machines that the modem uses
later on to see if that is still causing problems then the problem could be
with the DNS server. But right now I am going to sit the way it is and see
what happens.

Thanks again for the ideas but I had already done the power downs and power
ups that are recommended.

Al


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