[clug-talk] DNS woes

Carl ct at turner.ca
Mon Apr 3 16:04:41 PDT 2006


I picked up a wired Linksys router (BEFSR81) and connected it. And it
exhibited the same problem! ie, could get Internet connectivity but no
name resolution. And when I looked at the Linksys status page the DNS
severs were set to 0.0.0.0.

I swapped the router in and out of the network a few times. And each
time with my PC connected to the cable modem directly things worked
fine. But with a router in between (either the SMC or Linksys) DNS would
not work.

So I hooked up a hub as Gustin suggested and used Ethereal to see what
was happening.

I tried both the PC and SMC router. In both cases, the client would
request DHCP Option 6: Domain Name Server. But in the Shaw DHCP response
only the responses to the PC would contain the information for Option 6.
ie. the DNS servers.

Then I tried with the Linksys router and I noticed the Shaw response did
contain DNS server info! So I put my network back with the Linksys in
place and everything worked.

So then I put the SMC router back in (which was my original setup) and
now everything is working fine.

Talk about a wild goose chase. I'm guessing Shaw had a temporary issue
with their DHCP server but now it must be resolved?

Carl



On Mon, 2006-04-03 at 14:39 -0600, Darren L wrote:
> Let me know if you find a WRT54Gv4!
> 
> 
> 
> On 4/3/06, Carl <ct at turner.ca> wrote:
>         The front end on the SMC has an option to release/renew the
>         IP. Each
>         time it gets the same IP though. And each time the DNS servers
>         are
>         0.0.0.0.
>         
>         It is funny how this problem just showed up today after many
>         months of 
>         using the SMC router.
>         
>         Anyway, since the problem is likely in the SMC firmware I
>         think I'll
>         just go out and purchase a new router. As you say it is
>         probably not
>         worth my time to trouble shoot. I am somewhat curious but if I
>         can't end 
>         up fixing the problem it will just frustrate me. One of the
>         big
>         downsides of using a closed source appliance.
>         
>         Thanks,
>         
>         Carl
>         
>         
>         
>         
>         
>         On Mon, 2006-04-03 at 13:21 -0600, Gustin Johnson wrote: 
>         > -----BEGIN PGP SIGNED MESSAGE-----
>         > Hash: SHA1
>         >
>         > Does the management front end on the SMC have an option to
>         release and
>         > renew the dynamic IP that Shaw assigns?  If this does not
>         populate the 
>         > DNS servers on the SMC router, then the problem is likely an
>         error in
>         > the SMC firmware.  Unless there is an updated firmware, you
>         may be
>         > better served by buying a new router (I have a couple of
>         linksys 
>         > wireless routers and a couple of linux boxes with different
>         distros that
>         > all work fine with Shaw, so you have a lot of choice here).
>         >
>         > Trouble shooting this is not really worth the time, since
>         you can't fix 
>         > the problem (The SMC is a closed appliance that you do not
>         have access
>         > to).  If buying a new $80 router fixes the problem, then it
>         is not even
>         > worth 1 hour of my time to troubleshoot.
>         >
>         > Of course if you are curious then it is worth the time.  It
>         would be 
>         > interesting to see the differences between the linux box and
>         the SMC,
>         > but from a curiosity/educational point of view, not really a
>         technical
>         > troubleshooting point of view.
>         >
>         > Ethereal is a neat tool, especially if have/are
>         reading/learning about 
>         > TCP/IP (Shawn, my review of that giant TCP/IP book should be
>         ready this
>         > week).
>         >
>         > An old fashioned hub is great in this case, since it repeats
>         packets to
>         > all ports, making it easy for Ethereal to capture them (ie
>         cable modem 
>         > to hub, then both the linux box and SMC router to the hub).
>         >
>         > Cheers
>         > __
>         >
>         >
>         > Carl wrote:
>         > > My home network has decided to stop resolving names today.
>         Eg. If I ping 
>         > > google.com I get unknown host yet if I ping 64.233.167.99
>         I get
>         > > responses. If I enter host google.com I get:
>         > > ;; connection timed out; no servers could be reached
>         > >
>         > > I have several computers connected to an SMC router which
>         is connected
>         > > to a Shaw cable modem. The computer I have using now is
>         running Fedora 
>         > > core 3.
>         > >
>         > > While connected through the SMC Barricade router
>         my /etc/resolv.conf is:
>         > >
>         > > ; generated by NetworkManager, do not edit!
>         > > search cg.shawcable.net
>         > > nameserver 192.168.2.1
>         > >
>         > > If I browse to 192.168.2.1 on the status page, among other
>         things I see: 
>         > >
>         > > Primary DNS: 0.0.0.0
>         > > Secondary DNS: 0.0.0.0
>         > >
>         > >
>         > > If I connect my computer directly to the cable modem
>         things are good, 
>         > > name resolution works and and my /etc/resolv.conf looks
>         like:
>         > >
>         > > ; generated by NetworkManager, do not edit!
>         > > search cg.shawcable.net
>         > > nameserver 64.59.135.133
>         > > nameserver 64.59.135.135
>         > >
>         > >
>         > > To me it seems like the SMC router is not getting the DNS
>         information 
>         > > correctly from the Shaw DHCP server. I phoned Shaw and
>         they said it is a
>         > > problem with my SMC router. I talked to SMC tech support
>         and they got me
>         > > to manually enter the DNS servers and then it works. I
>         don't want to 
>         > > have to manually setup the DNS config but they offer no
>         other solution.
>         > >
>         > > Does anyone know why the SMC router might have trouble
>         receiving the DNS
>         > > info? How can I trouble shoot this? Would using Ethereal
>         to see what is 
>         > > happening be worthwhile?
>         > >
>         > > Thanks,
>         > >
>         > > Carl
>         > >
>         > >
>         > >
>         > >
>         > >
>         > >
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