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From: David on 25 Apr 2008 10:58
Background:

I have several XP Home/Pro systems on my home LAN. All have private,
hard-coded IP addresses (192.168.1.x). There is a ZyXel hardware
firewall/VPN router between my LAN and my ISP's cable modem. The ZyXel gets a
DHCP-assigned IP address from the ISP (Comcast), but nothing else.
Specifically, it doesn't have the ability to retrieve the addresses of
Comcast's DNS Servers, and thus it's not possible for it to propagate those
addresses to my LAN systems. Thus, I have to hard-code the DNS server
addresses on my home systems. But that's worked OK for several years.

The problem(s):

Last week, Comcast apparently changed their DNS servers (I can no longer
ping the old ones). No big deal, except that Comcast now refuses to give me
the addresses of their new DNS servers!!! (although Time Warner - who I had
been with before Comcast bought them out last year - happily gave out their
DNS server addresses).

So I used nslookup to poke around and find the addresses of what I think are
Comcast's new DNS servers. But when I configure my home systems to use those
DNS server addresses and then ping a host by name (eg, www.rice.edu) the name
resolution fails*, although I can use nslookup to resolve that same name!
(and I can ping the DNS servers by their addresses)

* that is, it gets an error trying to resolve the name, even before
attempting to issue the ping.

Thinking that Comcast's servers were doing something strange, I configured a
home system to use one of the Root DNS servers at VeriSign, but the name
resolution still fails when I try to ping anything by name

So, if I can resolve names using nslookup, then why can't XP resolver do the
same?

Are there XP firewall settings that might be blocking the DNS server replies
(although if that were true, then why doesn't it block nslookup and why did
it just now begin failing?)

Were there any recent Windows Updates to the XP resolver?

And what settings should I be using for the "Append DNS suffixes" on the
DNS tab of the Advanced TCP/IP Settings? And also for the
registration-related checkboxes at the bottom of that tab? I've never really
understood what these did in my configuration.

Thanks (my daughter will really be happy when Dad gets "the Internet" fixed!)

D



From: John Wunderlich on 25 Apr 2008 15:59
=?Utf-8?B?RGF2aWQ=?= <David(a)discussions.microsoft.com> wrote in
news:C9500FBD-1F11-4419-9407-1796DC27DB21(a)microsoft.com:

> Background:
>
> I have several XP Home/Pro systems on my home LAN. All have
> private, hard-coded IP addresses (192.168.1.x). There is a ZyXel
> hardware firewall/VPN router between my LAN and my ISP's cable
> modem. The ZyXel gets a DHCP-assigned IP address from the ISP
> (Comcast), but nothing else. Specifically, it doesn't have the
> ability to retrieve the addresses of Comcast's DNS Servers, and
> thus it's not possible for it to propagate those addresses to my
> LAN systems. Thus, I have to hard-code the DNS server addresses
> on my home systems. But that's worked OK for several years.
>
> The problem(s):
>
> Last week, Comcast apparently changed their DNS servers (I can no
> longer ping the old ones). No big deal, except that Comcast now
> refuses to give me the addresses of their new DNS servers!!!
> (although Time Warner - who I had been with before Comcast bought
> them out last year - happily gave out their DNS server addresses).
>
> So I used nslookup to poke around and find the addresses of what I
> think are Comcast's new DNS servers. But when I configure my home
> systems to use those DNS server addresses and then ping a host by
> name (eg, www.rice.edu) the name resolution fails*, although I can
> use nslookup to resolve that same name! (and I can ping the DNS
> servers by their addresses)

It's best not to guess at stuff like this. You must know someone else
in your city that has Comcast and uses it in a more conventional way.
Visit them and either use "ipconfig" to give you the addresses of the
DNS servers (if they don't use a router) or if they use a router, go to
their Router's status page and look at the DNS server that was set by
DHCP.

Other than that, you can try using the OpenDNS routers and see if that
will work for you:
<http://en.wikipedia.org/wiki/OpenDNS>

[....]
>
> So, if I can resolve names using nslookup, then why can't XP
> resolver do the same?

Don't know. It's possible that nslookup has remembered a default DNS
server that works and is different than your current configuration? If
you just type "nslookup" without parameters, what does it show as its
default server? Does it match your settings?

> And what settings should I be using for the "Append DNS suffixes"
> on the DNS tab of the Advanced TCP/IP Settings?

This is a "feature" used by many ISPs. If you type in a Non-Fully
Qualified Domain Name (i.e. one without any "."s), then Windows will
add the domain names in this list to your non-FQDN name until a match
is found in the DNS. This is a feature frequently used by ISPs when
connecting to mail servers and the like... they just tell you to use
"SMTP" as the server name, then they add region-specific suffixes (set
as part of DHCP) in this table so that you will automatically connect
to your local server - whatever that might be.

> And also for the
> registration-related checkboxes at the bottom of that tab? I've
> never really understood what these did in my configuration.

Used mainly in companies that have an internal Dynamic DNS servers.
When you connect to the network, your computer name is automatically
registered in the DNS so that other machines can connect to yours if
they know your computer name.


HTH,
John
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