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Can't connect to Web



 
 
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  #16  
Old May 29th 17, 05:20 AM posted to microsoft.public.windowsxp.general,alt.comp.os.windows-xp,comp.os.ms-windows.networking.misc
rickman
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Posts: 14
Default Can't connect to Web

VanguardLH wrote on 5/28/2017 4:11 PM:
Stef wrote:

Steve Hayes wrote:

This morning I suddenly lost my connection to the web while I was
browsing.

Mail still worked, news still worked, but the web connection did not.

I reset the router, rebooted my computer, but still nothing.

I wondered if it was a browser fault (I use Firefox) so tried Internet
Explorer. It too could not connect, but offered to run diagnostics.
This is what was found:

---- diagnostic report ----
[snip]


DNS Client Diagnostic
DNS - Not a home user scenario

info Using Web Proxy: no
info Resolving name ok for (www.microsoft.com): yes
No DNS servers

DNS failure


I haven't read the entire thread, but this is mostly likely your
problem.

Your default Domain Name Server is down or can't be accessed. When you
can't access "The Web" with your browser, but mail, ftp, etc work
(they don't use DNS), that's where I'd start the troubleshooting.


WRONG. Anytime you use a hostname (host.domain.tld) to specify a host,
like for an e-mail or ftp or "etc" server, DNS gets used. Humans like
names. Computers demand numbers. How many times have you encountered a
user that specifies the IP address address for their e-mail server when
configuring an account within their local e-mail client? Look at your
own e-mail config in whatever local e-mail client you use. Did you
enter a hostname or an IP address? Unless you do the DNS lookup when
configuring the e-mail account in your e-mail client, you don't get that
info from the e-mail provider as they give you hostnames. How many web
pages have you visited where absolute references (non-relative or just a
path under the current location) to sources in a web page use IP
addresses instead of hostnames? If DNS were unusable to the OP, he
wouldn't be doing e-mail or newsgroups. If the OP were having to use IP
addresses for everything, he would've mentioned it and maybe how he got
those IP addresses.


Not 100% true. I believe the Eudora email client uses DNS once to lookup
the IP address of the email server(s) when it first accesses them. From
then on it uses that stored IP address. There were times when I have ported
my domain to new hosting and the browser always finds the web site once it
is back up. But the email program seems to continue to access the old
servers until I do something to make to do a DNS lookup again (like restart
it).

--

Rick C
Ads
  #17  
Old May 29th 17, 05:27 PM posted to microsoft.public.windowsxp.general,alt.comp.os.windows-xp,comp.os.ms-windows.networking.misc
Stef
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Posts: 364
Default Can't connect to Web

On 28/5/2017 18:53, Steve Hayes wrote:

On Sun, 28 May 2017 17:16:01 +0000 (UTC), Stef
wrote:

Google's web site is hardly ever down. It's a good place to test if
your DNS is down using its IP addresses. You may get some kind of
error notice, but as long the number IP address you entered is replaced
with a URL with "google" in it, it's working even if typing in
www.google.com doesn't.

pinging both the domain name of a site and its IP address will test the
DNS, too.


Having read the replies to your post, I think the DNS thing is
unlikely, but last week Google appeared to be down quite a bit, but
only in some places. I had to resort to Bing for searches, and was
quite surprised at how quickly it appeared, much faster than Google,
probably because it has less traffic. Sites that connect to Google
were also much slower to load -- they seemed to hang until the Google
connection timed out.


Perhaps, the problem is something other than DNS, but since "it" failed,
it's a good place to start.

Google is a huge, busy site and I'm sure gets lots of DoS attacks, but
it's up the vast majority of the time and good to test if DNS is down or
it's something else. I used to use Yahoo, but it's regularly slow
responding and times out or I get tired of waiting. At least where I am
-- Southwestern US.

I've abandoned Google for searches and now use duckduckgo.com. Fast,
seems up all the time and doesn't profile searchers. I don't and NEVER
will use Bing: Part of my many personal protests against Microsoft and
its business practices. I only use Windows when I have no other
choices.

Stef
  #18  
Old May 29th 17, 07:57 PM posted to microsoft.public.windowsxp.general,alt.comp.os.windows-xp,comp.os.ms-windows.networking.misc
Stef
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Posts: 364
Default Can't connect to Web

On 28/5/2017 13:11, VanguardLH wrote:

Stef wrote:

Steve Hayes wrote:

This morning I suddenly lost my connection to the web while I was
browsing.

Mail still worked, news still worked, but the web connection did not.

I reset the router, rebooted my computer, but still nothing.

I wondered if it was a browser fault (I use Firefox) so tried Internet
Explorer. It too could not connect, but offered to run diagnostics.
This is what was found:

---- diagnostic report ----
[snip]


DNS Client Diagnostic
DNS - Not a home user scenario

info Using Web Proxy: no
info Resolving name ok for (www.microsoft.com): yes
No DNS servers

DNS failure


I haven't read the entire thread, but this is mostly likely your
problem.

Your default Domain Name Server is down or can't be accessed. When you
can't access "The Web" with your browser, but mail, ftp, etc work
(they don't use DNS), that's where I'd start the troubleshooting.


WRONG. Anytime you use a hostname (host.domain.tld) to specify a host,
like for an e-mail or ftp or "etc" server, DNS gets used. Humans like
names. Computers demand numbers. How many times have you encountered a
user that specifies the IP address address for their e-mail server when
configuring an account within their local e-mail client? Look at your
own e-mail config in whatever local e-mail client you use. Did you
enter a hostname or an IP address? Unless you do the DNS lookup when
configuring the e-mail account in your e-mail client, you don't get that
info from the e-mail provider as they give you hostnames. How many web
pages have you visited where absolute references (non-relative or just a
path under the current location) to sources in a web page use IP
addresses instead of hostnames? If DNS were unusable to the OP, he
wouldn't be doing e-mail or newsgroups. If the OP were having to use IP
addresses for everything, he would've mentioned it and maybe how he got
those IP addresses.


NOT ALWAYS. I'm old school. I use traditional, dedicated email, ftp,
usenet clients instead of a browser for all that. And those clients
work just fine even when my DNSes are not reachable which is very,
very rare. FWIW, Even when I enter the server names like
mail.mymailprovider.com in the configs, they still work without a
DNS. I think the client gets the IP and stores and uses it after
that. I never bothered to check and all have been working fine for
almost 5 years without any problems. With the usenet client I enter
the actual IP addresses. PS. Linux is my primary system and Internet
access. Windows runs in a VM on that machine for those times I need
it.


Here's a couple articles

https://www.lifewire.com/find-the-ip...eb-site-818155


Requires DNS be working.


Yes, but the article also includes some IPs for testing.

https://www.lifewire.com/what-is-the...-google-818153


Requires DNS be working.


Yes, but the article also includes some IPs for testing.

Also, if DNS was unusable, how would the OP get to the lifewire site?
You didn't give him the IP address for that site.


I was going to include it for testing purposes, but when I tested it
myself to be sure it worked, it didn't. Don't know why. Didn't check
why. either. Other IPs for the articles I tested did work though.


Stef
  #19  
Old May 29th 17, 08:05 PM posted to microsoft.public.windowsxp.general,alt.comp.os.windows-xp,comp.os.ms-windows.networking.misc
Stef
external usenet poster
 
Posts: 364
Default Can't connect to Web

On 28/5/2017 10:48, Bert wrote:

In news
but mail, ftp, etc work (they don't use DNS),


Unless the IP addresses for the servers are hard-coded into the client,
they certanly do.


I enter IP addresses sometimes. Just enter and save them. But even
when I enter the server "name," I think my email and ftp clients lookup
the IP address on first access and store them for future use, so it
doesn't have to look it up each time. The reason I say this is even
when my DNSes are "down" those clients (and usenet clent, too) still
work. I don't use a web browser for those tasks.

Stef

  #20  
Old May 31st 17, 06:51 PM posted to microsoft.public.windowsxp.general,alt.comp.os.windows-xp,comp.os.ms-windows.networking.misc
Bert[_3_]
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Posts: 217
Default Can't connect to Web

In news
But even when I enter the server "name," I think my email and ftp
clients lookup the IP address on first access and store them for
future use, so it doesn't have to look it up each time


If they do, it's a bad idea.

Many large-scale systems (and some small ones) have multiple IP
addresses and rotate the way they appear to DNS requests in order to
balance user load.

They'll also take addresses out of rotation if systems are down.

--
St. Paul, MN
  #21  
Old May 31st 17, 09:41 PM posted to microsoft.public.windowsxp.general,alt.comp.os.windows-xp,comp.os.ms-windows.networking.misc
VanguardLH[_2_]
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Posts: 10,881
Default Can't connect to Web

Steve Hayes wrote:

Having read the replies to your post, I think the DNS thing is
unlikely, but last week Google appeared to be down quite a bit, but
only in some places. I had to resort to Bing for searches, and was
quite surprised at how quickly it appeared, much faster than Google,
probably because it has less traffic. Sites that connect to Google
were also much slower to load -- they seemed to hang until the Google
connection timed out.

From people I asked, it seemed that Google's servers in the east of
South Africa and in New Zealand were down, but not in the UK or USA.


You might also trying to find out if the route you happen to get is
actually usable to you. Routing is not dynamic: when you can't get
through one route to a target, you don't automatically get assigned a
different route to try. Hosts (nodes in a route) go down, become
unresponsive, or get too busy so they are excessively slow and clients
will timeout. Updating the routing tables (once the problem has been
reported and after someone takes action) can take about 4 hours (that's
usually how long I wait for routing problems but they can take a lot
longer).

Run a traceroute (tracert) to see if you can reach the target host. For
example, last night I could not get to boatloadpuzzles.com. The web
browser said the site was unresponsive. Not true. A traceroute should
I wasn't even getting outside my own ISP's network. Something weird was
happening where I kept getting looped back through the same two nodes.
I could get to other sites, like yahoo.com, but not to that one site.
It wasn't a site problem. It was a routing problem so I wasn't even
reaching the site.

You can use public proxies to reach a site using different routes. I
once couldn't reach creative.com for several days. I could get there
okay using a public proxy. Why? The route that I got happened to hit
one of their boundary servers (front end) to their web farm that was
down. The other routes hit different boundary servers so I could get
in. When presented with the various routings (mine that was unusable
and others that worked) to show which boundary host was unresponsive,
they fixed the problem in a day.

Another time I couldn't get to any site on the west coast but I could
get elsewhere. Turns out an entire backbone provider (Sprint) had an
outage so no one could go either direction across most of the Rockies.
I reported the problem but they already knew. That was a short-lived
outage but not when you're sitting at your computer wondering why you
can't get somewhere.

By the way, and back to the DNS topic, there is a possiblity that it
will interfere with visiting a site but not because the DNS server is
down but because the site might've changed their IP address and you're
still trying to use the old lookup from the local DNS client's cache.
TTL (time-to-live) entries for successful lookups (positives) last
longer in the DNS client's cache than those for failed lookups
(negatives). Some users might suggest disabling the DNS Client service
but that means your end has to do more DNS lookups. Without the cache,
every hostname has to be looked up even if it is the same one. A web
page can have hundreds of references requiring a DNS lookup. Having to
send a request to a DNS server and get a response takes time. Looking
it up in a local cache is much quicker. By default in Windows, the TTLs
a

positive TTL = 24 hours
negative TTL = 5 minutes

You can modify those DWORD values in the registry.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\DNSCache\Parameters

MaxCacheEntryTtlLimit (positive TTL), default = 86400 seconds (24 hours)
NegativeCacheTime (negative TTL), default = 300 seconds (5 minutes)
(if the entries are absent, the defaults get used)

Some folks set the negative TTL to zero to not cache any of the failed
DNS lookups. Their intent is to keep requesting new lookups from the
DNS server until they happen to get one that works. They're hoping to
get to the site as soon as the DNS records get updated. Seems a bit
rude but I can see reducing this to one minute. The positive TTL is a
bit overly long since it is possible a site has changed their IP address
inside of a day. An hour or two seems more appropriate.

If you suspect there is a problem with the Windows DNS cache, you can
flush it so start over with all new DNS lookups and new cachine. Run:

ipconfig /flushdns

Note that web clients can incorporate their own internal DNS cache which
overrides the defaults defined in the registry. The client uses its own
DNS cache instead of relying on the one in Windows. Firefox has its own
DNS cache. I suspect that is partly due to Firefox being
cross-platform: they want to rely on their own DNS cache instead of
hoping there is one (and still functional) back in the OS. I forget why
I ran into problems with Firefox's own DNS cache but back then I
disabled it to resolve whatever was the problem. I have not disabled
the DNS Client in Windows so that DNS caching is available and I don't
want (and ran into problems with) Firefox's own internal DNS cache. In
about:config, Firefox's TTL setting is at:

network.dnsCacheExpiration
default = 3600 (1 hour)
0 (zero) disables Firefox's DNS cache

Setting to zero means disabling the cache which flushes all currently
cached DNS lookups. Apparently Firefox is only caching positive
results, not negative ones. You could then reset back to 3600 or a
value of your choice or just leave it zero (and rely on the DNS Client
in Windows to do both positive and negative DNS caching). There are
add-ons for Firefox to flush Firefox's internal DNS cache, like DNS
Flusher, but I disabled Firefox's internal DNS cache so I don't need an
add-on to fix DNS caching problems within Firefox.

In Firefox, I also set network.dns.disablePrefetch = True but that's for
a different DNS issue: Firefox populating its internal DNS cache for any
resources specified in the currently loaded page. This has Firefox
prefetching IP addresses from the DNS server for resources that you may
never need, like a hyperlink to another site that you won't be visiting
or for ad or tracking sources that can then see your IP address visited
them. You might use an adblocker but prefetching in Firefox partially
cripples the adblocker from doing its job. See:

https://en.wikipedia.org/wiki/Link_p...and_criticisms
  #22  
Old June 1st 17, 12:03 AM posted to microsoft.public.windowsxp.general,alt.comp.os.windows-xp,comp.os.ms-windows.networking.misc
Stef
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Posts: 364
Default Can't connect to Web

On 31/5/2017 10:51, Bert wrote:

In news
But even when I enter the server "name," I think my email and ftp
clients lookup the IP address on first access and store them for
future use, so it doesn't have to look it up each time


If they do, it's a bad idea.

Many large-scale systems (and some small ones) have multiple IP
addresses and rotate the way they appear to DNS requests in order to
balance user load.

They'll also take addresses out of rotation if systems are down.


I really don't know for sure. I never bother checking. But I do know,
the few times the Web didn't work and I knew DNS, or lack thereof, was
the problem, I could still get mail, etc.

I think the OP is having a configuration problem more than anything
else. I used to have a side business troubleshooting such things on
Windows machines. Windows has an extraordinary ability to break
itself. When the printer or ethernet or wireless, etc. just stop
working, particularly when they worked fine before the machine was
"turned off" the night before, settings were the first thing I
checked.

Stef



  #23  
Old June 1st 17, 07:52 AM posted to microsoft.public.windowsxp.general,alt.comp.os.windows-xp,comp.os.ms-windows.networking.misc
Steve Hayes[_2_]
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Posts: 1,089
Default Can't connect to Web

On Wed, 31 May 2017 15:41:21 -0500, VanguardLH wrote:

If you suspect there is a problem with the Windows DNS cache, you can
flush it so start over with all new DNS lookups and new cachine. Run:

ipconfig /flushdns

Note that web clients can incorporate their own internal DNS cache which
overrides the defaults defined in the registry. The client uses its own
DNS cache instead of relying on the one in Windows. Firefox has its own
DNS cache.


Thanks for this and lots of other useful information.

Since my problem was with the web and not mail or news, and I use
Firefox, it was probably not caused by the Windows DNS cache, but with
something in Firefox or even in my ISP. It seems to have come right
now, not necessarily because of anything I tried.


--
Steve Hayes
http://www.khanya.org.za/stevesig.htm
http://khanya.wordpress.com
  #24  
Old June 13th 17, 09:10 PM posted to microsoft.public.windowsxp.general,alt.comp.os.windows-xp,comp.os.ms-windows.networking.misc
Char Jackson
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Posts: 10,449
Default Can't connect to Web

On Wed, 31 May 2017 17:51:05 -0000 (UTC), Bert wrote:

In news
But even when I enter the server "name," I think my email and ftp
clients lookup the IP address on first access and store them for
future use, so it doesn't have to look it up each time


If they do, it's a bad idea.


Agreed. Thanks to DNS, if a remote host's IP address needs to change for
any reason, DNS will automatically find the new IP.

Many large-scale systems (and some small ones) have multiple IP
addresses and rotate the way they appear to DNS requests in order to
balance user load.


Typically referred to as "DNS load balancing", it's a free but very
crappy way to make a remote service available. Fortunately, it's pretty
rarely used these days. Instead, most publicly accessible organizations
use actual load balancers, where a remote FQDN resolves to a single IP
address that's configured on the client side of a load balancer. The
actual application servers reside behind the load balancer where they
can't be accessed directly by the public.

They'll also take addresses out of rotation if systems are down.


The main problem with DNS load balancing (simply adding additional A or
AAAA records for a given FQDN) is that DNS has no way to do application
health checks, so regardless of whether a specific server is up or not,
DNS will happily hand out its IP address. Real load balancers address
that issue by performing periodic application health checks, taking
servers out of rotation if they don't respond properly and then adding
them back into rotation when they start responding again.

  #25  
Old June 21st 17, 02:50 AM posted to microsoft.public.windowsxp.general,alt.comp.os.windows-xp,comp.os.ms-windows.networking.misc
Rene Lamontagne
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Posts: 2,549
Default Can't connect to Web

On 6/1/2017 1:52 AM, Steve Hayes wrote:
On Wed, 31 May 2017 15:41:21 -0500, VanguardLH wrote:

If you suspect there is a problem with the Windows DNS cache, you can
flush it so start over with all new DNS lookups and new cachine. Run:

ipconfig /flushdns

Note that web clients can incorporate their own internal DNS cache which
overrides the defaults defined in the registry. The client uses its own
DNS cache instead of relying on the one in Windows. Firefox has its own
DNS cache.


Thanks for this and lots of other useful information.

Since my problem was with the web and not mail or news, and I use
Firefox, it was probably not caused by the Windows DNS cache, but with
something in Firefox or even in my ISP. It seems to have come right
now, not necessarily because of anything I tried.





 




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