F10, NetworkManager, and intermittent dns

[Bill Davidsen]

McGuffey, David C. wrote:
> A couple of weeks back I did a fresh install of F10, blowing away F7.
> Got F10 up and running, did an update and then converted to static IP
> addressing.  Everything went downhill from there.  Could only get on the
> network about 1 out of 10 attempts. This is on a wired network.
> 
> Did some research and discovered on an Ubuntu forum a recommendation to
> pin the MAC address to an IP address in the dhcpd configuration of the
> IPS firewall/switch device, and then go back to dynamic addressing.
> 
> Did that, and did a complete fresh install of F10 with dynamic
> addressing.  Data held by NM seems to be correct. I can ping all the
> devices on the 192.168.1.0 network, and can use cups to print to two
> printers on that network.  I got to a mirror site and downloaded the F10
> updates and applied them. So far, so good. 
> 
> Most of the time, I can browse out and get Evolution to upload/download
> e-mail.  I say most of the time, because after a while, the box starts
> getting dns errors (failure to resolve address).  It is intermittent,
> and has been driving me nuts.
> 
> I finally discovered a pattern.  After a reboot, the first user can log
> in and everything works.  That user can log out and a second user log in
> and everything works. This can be repeated until the cows come home.
> However, if either of those users let the screensaver kick off, dns
> disappears for all users until a reboot. The Windoze XP Pro side of this
> box doesn't skip a beat. Two other Windoze laptops (one XP and one
> Vista) have no problems, and neither did a guest laptop on the wireless
> side of the ISP firewall/switch, so I don't think there is an issue with
> the ISP firewall/switch. 
> 
> This NM stuff is new to me.  The old way worked and worked and
> worked...better than the Energizer Bunny.  This NM tool, in my opinion,
> is not ready for big time, and there is not enough documentation so
> someone can come back and yell at me to rtfm.
> 
> Tonight I'm going to install tshark and see what I can discover in the
> network traffic.
> 
> Where do I start?  
> 
Start by booting and saving a copy of /etc/resolv.conf. Then let the screensaver 
kick in, resume, and look at the resolv.conf file again. Other things to save 
and check are (a) "netstat -rn" or your favorite similar command, (b) "ifconfig" 
to see if the network is working. From the original resolv.conf file you can see 
the nameserver address(es) and then see if you can reach them after DNS fails, 
assuming the resolv.conf file isn't getting hosed. If you ping they may not 
respond (mine don't), but if you get "no route to host" you have something else 
wrong.

Does your screensaver config kick the system to low power mode, or suspend it, 
or do anything but change the screen display?

-- 
Bill Davidsen <davidsen at tmr.com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot