Weird network problem

[Phil Dobbin]

On 05/26/2013 11:54 AM, Mikkel L. Ellertson wrote:
> On 05/25/2013 08:00 PM, Phil Dobbin wrote:
>> Hi, all.
>>
>> I've got several machines on a LAN behind a NAT with DHCP assigning
>> always the same addresses from a dynamic IP.
>>
>> A couple of days ago the IP changed & since then, one of the machines
>> running Fedora 17 always fails first time to connect to the network:
>> launch Thunderbird, no start screen, first attempt to check mail, it
>> tells me that there's no network connection, second attempt it connects.
>>
>> The scheduled DejaDup backup always fails with no network but will run
>> manually no problem. Firefox can't find Google but the Nagios
>> web interface is fine as is all the cli stuff (ping, ssh, etc).
>>
>> Most annoyingly, yum update goes through every mirror before partially
>> downloading part of the updates & if the updates are large, it takes
>> about three attempts to get them all installed.
>>
>> I'd like to clear this up naturally especially as in the next couple of
>> weeks I'll be upgrading this box to Fedora 18 & the last thing I need is
>> a dodgy network connection.
>>
>> All the machines below are on the same LAN & they all work fine after
>> the IP address change, it's only the Fedora box that's causing problems.
>>
>> Any help appreciated. I'm stuck.
>>
>> Cheers,
>>
>>   Phil...
>>
> Check your name server settings. Does /etc/resolv.conf have a name
> server that from the old IP address? Do you have one machine on the
> network that runs a catching name server and the rest of the Fedora
> machines are looking for it at the old address? Or are you running
> something like dnsmasq on the machines, and have the old IP address
> in the config file?

I've never used any name server settings on any of these machines. The
lease is automatically assigned by DHCP so therefore there is no need to.

The external link comes into a NAT router then onto a HP ProCurve switch
& then via cat5 cables to each machine (there's no wireless involved
anywhere). Then each machine in Network Settings uses the automatic
setting to assign each address & DNS (192.168.1.254) & address mask
(255.255.255.0).

As I've said, all other machines (all 16 of them) are fine. It's just
the Fedora box which leads me to suspect that Fedora's doing, or not
doing something, to cause this.

Cheers,

  Phil...

-- 
currently (ab)using
CentOS 5.9 & 6.4, Debian Squeeze & Wheezy, Fedora Beefy, Spherical &
That Damn Cat, Lubuntu 12.10, OS X Snow Leopard & Ubuntu Precise,
Quantal & Raring
GnuPG Key : http://www.horse-latitudes.co.uk/publickey.asc