I have a Lenovo z51-70 running Ubuntu 15.04 and have bought the USB dongle as there are known driver issues in Ubuntu with the on board device. I have permanently disabled the onboard wi-fi wlan0 in /etc/network/interfaces (inserting iface wlan0 inet manual). I have the laptop 2 m away from the router and have a strong signal. When the computer is first started and Firefox launched I can load maybe two or three pages in succession, but after this Firefox a Server not Found message and the connection is lost. Reconnection is impossible until the laptop is restarted.
I’m operating on a DHCP home network Class A. Router is a SKY hub address 192.168.01.
I’ve also got a Lenovo Thinkpad E530C running Ubuntu 14.04 LTS which I’m using now. I have tried this with the dongle too. The process I followed was…
Inserted dongle. Opened terminal and ifconfig revealed wlan0 Centronics and wlan1Realtek dongle. I disconnected wlan0 using the icon at the head of the display and in the terminal using sudo ifconfig wlan0 down. I then opened several webpages sequentially in Firefox, which it did, but after about the sixth page it then failed to open a page selected from my bookmarks and after some time trying reported Server Not Found. ifconfig reveals that no IP address is active and a ping of the router returned a sendmsg: No buffer space available.
The above process has the same result on my new Lenovo Z51-70 with a different onboard wi-fi card.
Incidentally, I tried the process a second time on my E530C because I couldn’t recall the ping message exactly and I was able to sequentially load c.20 pages before everything failed and I was able to verify the ping message.
I hope this helps.
PS I have recorded my desktop for one of these exercises and can provide this so that you can see my actions and terminal.
After pursuing the “sendmsg: No buffer space available” issue, I appear to have solved it on my 14.04 LTS Lenovo Thinkpad E530c by increasing the value of /proc/sys/net/core/wmem_max to 83886080 as advised in an Ubuntu thread. However, doing this on my new Lenovo Z51-70 with 15.04 OS increases the number of pages that can be addressed sequentially to >20, but it has the same result in that the system eventually disconnects, ifconfig reports no connection and pinging results in the same buffer message.