hardware of software problem? networking

  • Thread starter Thread starter John Smith
  • Start date Start date
J

John Smith

Most of the time, I am able to access the Internet via this
particular computer. But some of the time, I cannot. When this
happens (I did not change firewall setting or anything), I
cannot access google (neither IE nor Firefox would do it) or
ping yahoo. However, I am still able to access other computers
on my LAN. Other computers on the same network still have
Internet access.

Is this a hardware or software problem? I suspect this is a
hardware problem but how can I still have intranet access
while losing Internet access?
 
John said:
Most of the time, I am able to access the Internet via this
particular computer. But some of the time, I cannot. When this
happens (I did not change firewall setting or anything), I
cannot access google (neither IE nor Firefox would do it) or
ping yahoo. However, I am still able to access other computers
on my LAN. Other computers on the same network still have
Internet access.

Is this a hardware or software problem? I suspect this is a
hardware problem but how can I still have intranet access
while losing Internet access?
Click to expand...

It means DNS lookup is not working.

For example, try this. What I've done here, is lookup the IP
address for www.sun.com in advance. If you enter this in the URL
area of your web browser, you should see the Sun Microsystems
main web page.

http://72.5.124.61

If you opened a second browser window, and entered it the regular way

http://www.sun.com

and the web page did not appear, then you know that DNS (domain name service)
is not working. DNS translates www.sun.com into 72.5.124.61 .

When the computer is set up to obtain settings automatically
via DHCP, one of the things it should do, is get the address
of one or more DNS servers. The DNS servers are what is
consulted, to do the above translations.

I've had problems before with my ISP, where the provided DNS
servers are broken. By manually configuring DNS on my computer,
I'm able to bypass the bad DNS server. But to do that, I have
to figure out in advance, where one of my ISP's main DNS servers
are located.

Since my ISP uses many DNS servers now, and the DNS servers
are arranged according to public IP address, I can simply
disconnect from ADSL, then reconnect, and I get a brand new
combination of public IP and DNS servers. So if I detect a problem
like that, it takes about 20 seconds to fix it.

If you open a DOS box, try the following command

nslookup www.sun.com

That command should consult the DNS server, for a translation
of the address given as an argument. The results returned, will
also tell you which DNS server was used to get the answer. If
your computer is actually asking your router to do the translation,
then use the web browser interface to your home router box, to
find out the DNS server address currently being used. The
status web page for my router, shows which DNS servers are
being used. (Recording those addresses, will give you addresses
for future use, if your DNS is failing.)

A DNS problem can be caused by misconfiguration at your ISP. It
could also be caused by buggy firmware on your router. (I used
to have a Linksys BEFSR41, and the last firmware I installed,
before getting rid of it, had a problem with the DNS failing.
It would fail, after the BEFSR41 had been running for a period of
time. The replacement router from another company, has no
problems at all.)

HTH,
Paul
 
Paul said:
It means DNS lookup is not working.

For example, try this. What I've done here, is lookup the IP
address for www.sun.com in advance. If you enter this in the URL
area of your web browser, you should see the Sun Microsystems
main web page.

http://72.5.124.61

If you opened a second browser window, and entered it the regular way

http://www.sun.com

and the web page did not appear, then you know that DNS (domain name
service)
is not working. DNS translates www.sun.com into 72.5.124.61 .

When the computer is set up to obtain settings automatically
via DHCP, one of the things it should do, is get the address
of one or more DNS servers. The DNS servers are what is
consulted, to do the above translations.

I've had problems before with my ISP, where the provided DNS
servers are broken. By manually configuring DNS on my computer,
I'm able to bypass the bad DNS server. But to do that, I have
to figure out in advance, where one of my ISP's main DNS servers
are located.

Since my ISP uses many DNS servers now, and the DNS servers
are arranged according to public IP address, I can simply
disconnect from ADSL, then reconnect, and I get a brand new
combination of public IP and DNS servers. So if I detect a problem
like that, it takes about 20 seconds to fix it.

If you open a DOS box, try the following command

nslookup www.sun.com

That command should consult the DNS server, for a translation
of the address given as an argument. The results returned, will
also tell you which DNS server was used to get the answer. If
your computer is actually asking your router to do the translation,
then use the web browser interface to your home router box, to
find out the DNS server address currently being used. The
status web page for my router, shows which DNS servers are
being used. (Recording those addresses, will give you addresses
for future use, if your DNS is failing.)

A DNS problem can be caused by misconfiguration at your ISP. It
could also be caused by buggy firmware on your router. (I used
to have a Linksys BEFSR41, and the last firmware I installed,
before getting rid of it, had a problem with the DNS failing.
It would fail, after the BEFSR41 had been running for a period of
time. The replacement router from another company, has no
problems at all.)

HTH,
Paul
Click to expand...

Thanks for the reply.

You are right. The DNS is not working. The problematic pc has
only one DNS in file. The working pcs have two DNS. I added
the second DNS to the problematic pc and now it has access to
Internet. Thank you.
 
Back
Top