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Old 12-05-2012, 03:48 AM   #1
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Registered: Apr 2004
Location: Potchefstroom, South Africa
Distribution: Fedora 17 - 3.3.4-5.fc17.x86_64
Posts: 1,506

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Strange connection problem - 3G USB dongle

Hi Guys

Please comment...

I have a 3G USB dongle from an ISP that has been working 100% fine for months.

Since the last few days though, it is exhibiting a strange problem on my FC13 laptop. If I try to connect 5 times (doesn't matter what - web, SSH, etc.) through it, the connection will fail 4 times and work the 5th time.

This is if I use symbolic names that have to be DNSed.

If I use straight IP addresses, it works perfectly, every time. I have already tried many different DNS servers in resolv.conf, most of the time, when using a symbolic name, however, connectivity will fail.

Straight IP addresses keep working perfectly.

If I am SSH'ed in for example (even to a symbolic name, if it works, that time) the connection is smooth and fast and never drops.

It is just the initial name -> ip thing that doesn't work 90% of the time anymore...

Here's my current resolv.conf:

options timeout:30
options attempts:5
options rotate
Where can I start looking? I don't think it is my ISP (since the connection works fine, as long as you restrict yourself to using IP addresses, and, once connected, it works beautifully, for hours and hours).

I've already tried dozens of other DNS servers than those above.

Oh yes, nslookup works perfectly when looking up any name, first time, ever time... Even when my ftp, ssh client or FireFox won't connect to a symbolic name, at that moment nslookup resolves the name to its ip, perfectly...

I also tried removing rotate above in my resolv.conf and then manually rotated the servers through the first position, no effect. I sometimes have to retry a connect to a symbolic name (be it SSH, FTP, WWW, etc) up to 20 times before getting connected. IPs work first time...

So I'm totally out of ideas to try.

What else can I look at?


Last edited by rylan76; 12-05-2012 at 03:56 AM.
Old 12-08-2012, 08:51 AM   #2
Registered: Dec 2012
Posts: 32

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Before connecting to internet, type the following command in a terminal:

 tail -f /var/log/messages
Now, try to connect and watch in the terminal if your connection gets the correct informations (local IP address, remote IP address, etc...)
Old 12-10-2012, 12:55 AM   #3
Senior Member
Registered: Apr 2004
Location: Potchefstroom, South Africa
Distribution: Fedora 17 - 3.3.4-5.fc17.x86_64
Posts: 1,506

Original Poster
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Thanks for replying!

It appears to have been the DNS servers I had in /etc/resolv.conf - I googled some free DNS services' IPs and shuffled the list in /etc/resolv.conf, placing one server after the other in the first position.

After awhile of trying this, everything suddenly started working - even though the DNS server in the top position had been there a few times before as I kept trying.

Anyway, it is working now... so I'm still not sure if it was the DNS servers or some errror at my ISP...


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