resolv.conf wrongly gets Belkin router's address

Kent West wrote:
> I replaced a dead router the other day with a new Belkin F5D7230-4
> wireless/4-port unit.

First let me say that I am not familiar with that particular piece of
hardware.

> When networking starts on my Etch box, /etc/resolv.conf gets rewritten
> like so:
>
> search hydroplatenet
> nameserver 192.168.2.1
> nameserver 208.180.42.68
> nameserver 208.180.42.100

I assume this interface is configured using DHCP? Are you using
'resolvconf'? What is in your /etc/network/interfaces file for that
interface?

> Web browsing (and other name-dependent Intarweb Pipes stuff) is very
> slow with these settings, but if I comment/remove the first nameserver
> line, which is the address of the Belkin router, things are fine.

Some routers proxy DNS information through themselves. On the boxes I
have seen that do this it is configurable and can be turned off. It
appears to me from reading your report that the Belkin box has offered
its own address as a DNS server in addition to some upstream DNS
server.

Inspect the Belkin client DNS configuration and see if that address
has been added to the configuration or if there is a way to remove
that configuration. On consumer routers I have worked with it has
always been possible to specially add in a set of DNS addresses to
provide to DHCP clients, by default empty. Hopefully in your case
these can be removed specifically. Although it is a terrible thing
that it came out-of-the-box with a bad configuration.

> I found a couple of other people with similar problems
> (http://ubuntuforums.org/showthread.php?t=297834 and
> http://www.mepis.org/node/3221), one of which provided the kludgey fix
> of pre-pending the good addresses via /etc/dhcp3/dhclient.conf to force
> duplicates of the good address to the top of the file, but that's just ugly.

And you could also completely override the dns addresses provided by
dhcp or you could move to static addresses. In both cases you are not
getting good use out of the box.

> I've sent this problem to Belkin, and their tech support responded that
> "The Belkin Router only provides a Gateway address but is not a DNS
> server"

Then why did it offer itself as one through DHCP? That could be a
confirmation of a bug.

> (http://www.belkin.com/contact/milan/default1.aspx?id=5B5B5956095F560D0D5C5F0E5B0A5D56305F5E).

Note: That web url has expired.

> They indicated that I should call them on the phone (I hate dealing with
> stuff over the phone...), but I wanted to get all my ducks in a row
> before I do so.

If they hear Debian GNU/Linux they will probably drop your support
call immediately too. Sigh. It would be useful to crosscheck this
with tests from other operating system clients. If they all behave
the same then you have confirmation. If they behave different then
that is also useful information.

> Is Debian somehow responsible for incorrectly seeing this "Gateway
> address" as a name server address (and if so, how do I fix it), or is
> the Belkin tech supporter incorrect about his product (or some other
> option)?

When you say Debian here you really should say dhcp3 client or pump or
other specific dhcp client that you have installed. If you don't know
then you are probably using dhcp3. Debian just bundles it up for you.

I believe that the Belkin DHCP server is offering itself as a DNS
server inappropriately. Yours is not the only report of the problem.
It may be possible correct the bad configuration by explicit
configuration of the box to avoid this.

Commodity routers such as those are inexpensive. Return yours and buy
a different brand that works correctly and avoid the problem.

Bob

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Kent West wrote:
> > auto eth0
> > iface eth0 inet dhcp

That looks fine to me.

> That's the way it seems to me also, but when Belkin support told me that
> their router does NOT offer its own address as a DNS server, I figured I
> better double-check with other Debianistas before concluding that Belkin
> support doesn't know what they're talking about.

I have had really terrible experiences trying to get support for
commodity consumer hardware. You have my sympathy.

> I don't find any such settings; here's a snapshot of the only relevant
> page on the Belkin setup that I can find:
> http://www.acu.edu/~westk/belkin.jpg

That is what I expect to see but it does not explain why it is
offering itself as a DNS server. To me this is confirmation of the
bug.

To continue debugging this I would capture a network trace of the dhcp
transaction using 'tcpdump' and then decode it using 'ethereal'.
Ethereal has a decode module for most packet types and is a great tool
for debugging anything network related. I expect you would find
explicitly in the data packet the bad router address offerred as a dns
server. But perhaps now. Regardless it would be hard data.

I also see that 'dhcpdump' is packaged for Debian. I found it just
now by searching the package database. It looks interesting because
it is targeted and so perhaps "just the tool" for your problem. I
have never used it but it looks useful.

apt-cache show dhcpdump
Description: Parse DHCP packets from tcpdump
This package provides a tool for visualization of DHCP packets as
recorded and output by tcpdump to analyze DHCP server responses.

> Ag! I'm so dense. I'm so accustomed to being a Debian-only house that I
> forgot my work laptop is dual-boot with Vista. I'll give that a shot.
> Thanks!

It is very pleasant to hear that you can forget entirely about those
other systems. That is the way that it should be. :-)

Bob

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