I have upgraded our notebooks to 12.1 (kde), using identical and (from what I can tell) standard network settings over eth0 in several networks, using networkmanager. All additional updates are installed.
Now, for most dns requests (opening a web site, sending an e-mail to smtp, etc.) I very quickly get an error message, on the second identical try as well, and on the third identical try the expected response.
This happens both at times of very active use and at other times. It is independent of the router (as it happens both at work and at home).
Problems with DNS can be very specific to your ISP and your present Internet connection. One solution is not use the default DNS servers they provide but instead input your own. At my home, I just changed the DNS servers to use Google ones. And I did so in my router. You can change this directly in openSUSE as well, but for a laptop or netbook that moves around, it can be a problem changing this for different wireless connections that change all of the time. None the less, the first step is to know the DNS server addresses. Here is a listing that I have been using:
Google
8.8.8.8
8.8.4.4
Level 3 Communications (Broomfield, CO, US)
4.2.2.1
4.2.2.2
4.2.2.3
4.2.2.4
4.2.2.5
4.2.2.6
Verizon (Reston, VA, US)
151.197.0.38
151.197.0.39
151.202.0.84
151.202.0.85
151.202.0.85
151.203.0.84
151.203.0.85
199.45.32.37
199.45.32.38
199.45.32.40
199.45.32.43
GTE (Irving, TX, US)
192.76.85.133
206.124.64.1
One Connect IP (Albuquerque, NM, US)
67.138.54.100
OpenDNS (San Francisco, CA, US)
208.67.222.222
208.67.220.220
Exetel (Sydney, AU)
220.233.167.31
VRx Network Services (New York, NY, US)
199.166.31.3
SpeakEasy (Seattle, WA, US)
66.93.87.2
216.231.41.2
216.254.95.2
64.81.45.2
64.81.111.2
64.81.127.2
64.81.79.2
64.81.159.2
66.92.64.2
66.92.224.2
66.92.159.2
64.81.79.2
64.81.159.2
64.81.127.2
64.81.45.2
216.27.175.2
66.92.159.2
66.93.87.2
Sprintlink (Overland Park, KS, US)
199.2.252.10
204.97.212.10
204.117.214.10
Cisco (San Jose, CA, US)
64.102.255.44
128.107.241.185
logo2 Public DNS Servers
OpenNIC
202.83.95.227 (au)
119.31.230.42(au)
178.63.26.173 (de)
217.79.186.148 (de)
27.110.120.30(nz)
89.16.173.11 (uk)
69.164.208.50 (us)
216.87.84.211(us)
2001:470:8388:10:0:100:53:20 (us)
2001:470:1f10:c6::2 (us)
Based on how you connect to the internet and in how many places, your description might allow us to help in inputting the selected DNS servers. Again, at my house, I just put the DNS servers into my local router, thus not requiring any special openSUSE setup.
Thank you, I find it extremely unlikely that tinkering with my router or fixing the dns will be of any help. I have used these systems for years (actually since suse 5.1) and always been able to connect, under many different circumstances. Since networkmanager arrived, it has been sometimes more difficult, but I use it because I also connect a lot through wifi connections.
Now, all of a sudden, the upgrade to 12.1 creates this very odd behavious. It seems there must be some caching going on somewhere, that I don’t understand.
This is why I will rather not begin messing up stuff that has not been changed during the upgrade. Besides, I would only be able to do that here at home. In my work LAN, I am no admin, and the problem is exactly the same as at home.
So I would be happy to see someone explain to me where this comes from, and how I get to the root of the problem.
You can change DNS settings on your computer regardless of whether your the admin of the router or not. You can set that up in the NetworkManager profile. It will then ignore what You get from DHCP and set your setting so trying out the above suggestion might not be a bad idea at all.
Other than that I’ve read that kde settings from 11.4 are incompatible with 12.1 kde version. You can test this by creating a new user account or by renaming your .kde4 folder.
Finding the route cause of the problem will require looking at NetworManager logs and using a packet sniffer like wireshark or tcpdump. This can give You an idea what is actually happening with your DNS requests and if that really is the problem.