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Old 03-09-2010, 10:23 PM   #1
Zac Matthew Joseph
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Registered: Sep 2008
Distribution: pendrive- ubuntu, mandriva
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Ubuntu 9.10 unexpected internet behavior


I use DSL Broadband connection with all the IP and DNS settings. I realized that Sometimes when I start my system, internet works and sometimes it doesnt although wired connection is enabled on eth0. I gota restart many times then slowly internet starts.

But if I boot from pendrive the same ubuntu 9.10 catches internet without any IP or DNS settings! COOL ISN'T IT?
But on my hard disk installed system the same ubuntu 9.10 shows disconected network on eth0 if I dont give IP and DNS settings.

I would like to mention that i installed ubuntu 9.10 from pendrive itself and also that there are no IP conflicts with other PC.

Its not a big problem but i want to learn whats the deal here.

-Thank already
 
Old 03-10-2010, 03:41 AM   #2
tallship
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Quote:
Originally Posted by Zac Matthew Joseph View Post
I use DSL Broadband connection with all the IP and DNS settings. I realized that Sometimes when I start my system, internet works and sometimes it doesnt although wired connection is enabled on eth0. I gota restart many times then slowly internet starts.
um.. that's about as clear as mud. so you checked ifconfig and the DHCP server on the DSL router to make sure you're not assigning an IP that's reserved?

I see that you're running Windows Vista too.

Quote:
Originally Posted by Zac Matthew Joseph View Post
But if I boot from pendrive the same ubuntu 9.10 catches internet without any IP or DNS settings! COOL ISN'T IT?
Not really. Sounds like you have an issue that needs to be worked out.

Quote:
Originally Posted by Zac Matthew Joseph View Post
But on my hard disk installed system the same ubuntu 9.10 shows disconected network on eth0 if I dont give IP and DNS settings.
That's sounds correct. Set up your machine as a DHCP client if you don't want to set up via ifconfig and route.

Quote:
Originally Posted by Zac Matthew Joseph View Post
Its not a big problem but i want to learn whats the deal here.
Try using a packet sniffer to inform you as to what exactly is occuring. You'll learn a lot in the process too.

Last edited by tallship; 03-10-2010 at 03:42 AM.
 
Old 03-10-2010, 03:52 AM   #3
jamescondron
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Location: Scunthorpe, UK
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Walk me through this; how exactly does your computer connect? Straight into the wall and dialling up? Via a home router? One of those daft little USB 3g doodas?
 
Old 03-10-2010, 04:05 AM   #4
kainosnous
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Registered: Mar 2010
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There are a few things that you'll want to check to try to get an idea of what is going on. There could be many causes.

It seems like the unexpected behaviour is when it is not connecting, so when it doesn't connect, try to find out why. First, check ifconfig to see if you have an IP address (note what is is when it is working). You should also check /etc/resolv.conf to make sure that there is at least one nameserver listed. Another thing to check is your firewall by typing "iptables -L" to see what type of packets are being dropped or rejected.

One of the most useful tools would be a packet sniffer. I would recommend wireshark. That should tell help you see what is going around on your network.
 
Old 03-10-2010, 04:25 AM   #5
tallship
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And sometimes when you don't have a default gateway or an incorrect mask you can have weird, intermittant issues.

I was actually going to recommend Ethereal but forgot what it's name was changed to

Last edited by tallship; 03-10-2010 at 04:27 AM.
 
Old 03-10-2010, 11:47 PM   #6
everest40
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Quote:
Originally Posted by tallship View Post
And sometimes when you don't have a default gateway or an incorrect mask you can have weird, intermittant issues.

I was actually going to recommend Ethereal but forgot what it's name was changed to
I believe it's called Wireshark now
 
  


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