LAN Connectivity Only (Mint17) HP Elitebook 8570w [SOLVED]

[DogeIsFriend]

I wasn't sure which sub forum to post this in since it pertains to all adapters in my laptop losing connectivity.

I came into the office this morning and discovered my laptop was no longer connecting to the Internet after a weekend of working fine from home. I installed Linux Mint 17 last week around Wednesday and it has been working great so far up until this morning. The only changes made to the laptop over the weekend was the installation of Conky.

My wired network adapter is leasing an IP address and can communicate with network printers on this subnet but will not connect to the internet. I verified the wired network is function with a Windows PC and printed test pages from my Linux Mint laptop to a copier. The network is indeed operational. I tried to connect my laptop to two other known working WiFi networks and the issue is the same for both. I can lease an IP address and connect with good or better signal strength but cannot access the internet.

[txba516]

Hi DogeIsFriend,

There are two likely causes of the issue you are describing. Fortunately, both are fairly easy to resolve.

First, let's verify if you can reach a remote Internet IP address...
Test #1

Code: Select all

ping -c 4 4.2.2.1

If it is successful, then you should see this response...the time numbers will not match but as long as they are under say 100ms then all is well.

PING 4.2.2.1 (4.2.2.1) 56(84) bytes of data.
64 bytes from 4.2.2.1: icmp_seq=1 ttl=57 time=2.15 ms
64 bytes from 4.2.2.1: icmp_seq=2 ttl=57 time=2.03 ms
64 bytes from 4.2.2.1: icmp_seq=3 ttl=57 time=1.99 ms
64 bytes from 4.2.2.1: icmp_seq=4 ttl=57 time=2.11 ms

If that works, then let's test DNS resolution...
Test #2

Code: Select all

ping -c 4 google.com

And again, a successful ping test will have 4 replies from the resolved IP address associated with google.com (There are many so the IP may not match my example.)

PING google.com (64.233.185.138) 56(84) bytes of data.
64 bytes from 64.233.185.138: icmp_seq=1 ttl=46 time=2.70 ms
64 bytes from 64.233.185.138: icmp_seq=2 ttl=46 time=2.59 ms
64 bytes from 64.233.185.138: icmp_seq=3 ttl=46 time=2.59 ms
64 bytes from 64.233.185.138: icmp_seq=4 ttl=46 time=2.58 ms

Now...if for some reason both of these work fine but you still cannot get to the Internet in your web browser...the issue is likely not on your system.

If test #1 fails, then you do not have actual connectivity to the Internet. This will either be due to a misconfigured default route or blocking of access at the existing default route.
If test #2 fails, then the DNS servers that are configured are unreachable or incorrect.

You can quickly see what the settings are by looking at your network connection details in the System Settings -> Networking panel (Hardware subsection of System Settings).

Did this Mint installation properly reach the Internet at your office last week? Are you aware of any network changes that may have occurred at the office (new proxy/web filter/etc)?

Cheers!

[DogeIsFriend]

Thank you for the quick reply. My Mint installation was indeed working properly last week from this office. I haven't made any changes to the work network so I know that we didn't add any web filters or proxies.

Test 1 was successful and I was able to reach 4.2.2.1 without packet loss.
Test 2 was a failure and name resolution isn't working.

To rule out the network itself. I just disconnected my ethernet cable and connected my laptop to my 4G internet through my cell phone and repeated your test. I got the exact same results. I am able to ping the 4.2.2.1 address but I'm unable to resolve "google.com"

Doesn't that mean it's the computer itself? Thank you again for your assistance.

[txba516]

Yes, your configured DNS servers are not responding or not correct. You can either pull the configured DNS servers from a working system (Windows or other) and put those in your network setup or you can configure external DNS servers (those not in use at your office). The side effect of option 2 is that it may cause local name resolution problems if you use internal DNS for reaching computers on your office network.

Some external DNS servers I like to use are

208.67.222.222
208.67.220.220
4.2.2.1
8.8.8.8

Cheers!

[DogeIsFriend]

Thanks again for the reply. I configured my wlan0 interface to use the DNS servers you suggested. Name resolution still isn't working.

I didn't think it would be the DNS servers because three networks (1 wired, 2 wireless) using 3 different DHCP supplied sets of internal DNS servers met with the same results.

Is there way to delete my network adapters from my laptop and have Linux re-detect/reinstall them?

[txba516]

If you open a browser and go to http://64.233.185.138 does it show you the Google homepage?

It shouldn't be necessary but if you want to delete the NICs and have them be rediscovered, then open Network Connections, select the desired connection and click the Delete... button.

Upon reboot, the NICs should be rediscovered and configured with defaults.

Cheers!

[DogeIsFriend]

Browsing to http://64.233.185.138 does bring up the google.com homepage. DNS definitely isn't working but it's not the DNS servers that are causing the problem since 3 separate networks couldn't possibly all have malfunctioning DNS servers. My Windows and OSX clients are able to use all three of the networks I've been using to test my Mint17 laptop without any issues.

Something is broken with DNS for this laptop only and changing the DNS servers in the interfaces doesn't seem to help, no matter what I point to.

[txba516]

Ok so after some digging, I've come up with a fix for you I think.

By default, Ubuntu (and Mint) have a base version of dnsmasq that is run and managed by NetworkManager. Essentially, it positions itself as a local DNS resolver with the configuration set to forward requests upstream (to DHCP Assigned DNS servers) that it can't answer directly. This seems to be the point of the issue for you. I suspect that dnsmasq is not working or not forwarding requests.
The good news is we can remove it from the resolution stack with very little effort.

To disable the NetworkManager integrated dnsmasq component

Code: Select all

sudo gedit /etc/NetworkManager/NetworkManager.conf

Then comment out the dns=dnsmasq line by putting a # in front of it. Save the file and reboot.

This will set your laptop to directly query the DHCP obtained DNS servers.

Cheers!

[DogeIsFriend]

Back in business! Thank you for your time and diligence.