1

I'm on Ubuntu 15.04 with Chrome up to date. I've been having a strange problem recently.

My internet connection is wireless broadcasted from DSL (AT&T U-Verse to be exact). Viewed with ifconfig, my laptop had always identified with an IPV4 address. This morning as I've been having connection problems, it shows an IPV6 address.

Opening websites in Chrome was giving me ERR_NAME_NOT_RESOLVED, until I finally realized that I was having DNS issues (a common problem at my workplace). Normally I set our computers to Google Public DNS for IPv4, so naturally I set my IPv6 DNS resolvers to Google Public DNS's servers as well. After this, I've had a connection that can only be described as spotty.

Sometimes I can use Chrome to access sites like Google, Facebook, and Wikipedia, which are served over IPv6. Sometimes my network connection "dies," meaning first that Chrome shows a DNS_PROBE_FINISHED_NO_INTERNET and second that Ubuntu shows me the GTK notification that my network disconnected.

My connection "dies" after loading 2-3 IPv6 sites or while attempting to load an IPv4 site like http://ubuntu.com.

While I was on that computer, I would sometimes try to access a resource from Google Search, and then view it in Google cache: that worked (of course, only for a few page loads at a time).

Every time my connection "died" I would go to Network Manager and see the text "connecting." Sidenote: Network Manager does not show its icon in the "taskbar." I have to use Super and search to open it.

My router has an admin page at http://192.168.1.254, but most of the time there is an error when I try to access that page.

Here's what I've tried:

  1. Restart computer, many, many times.
  2. Restart router. I did this once, since it's quite disruptive to my workplace. All of the other computers (Windows and an iMac) seem to be doing fine.
  3. Renew DHCP lease. I've done almost all of these.
  4. Cleared Chrome's DNS cache.
  5. FireFox does not work any better.
  6. Connect directly to DSL modem with ethernet.

At the moment, my internet is working for IPv6 sites (I'm writing this question from the Mac). ping google.com yields connect: Network is unreachable (I can access google.com in Chrome), ping not-a-real-site.com yields ping: unknown host not-a-real-site.com, pinging my gateway at 192.168.1.254 gives "unreachable", as does pinging 8.8.8.8, but pinging localhost still gives the proper behavior.

I am very confused. How do I fix this?

Edit 0: I can connect to both https://ipv4.google.com and https://ipv6.google.com on the working computer, but only to https://ipv6.google.com on my laptop.

Improve this question

1 Answer 1

Reset to default
1

Knowing which method your ISP intended you to be using when accessing IPv4 servers would certainly help debugging the issue. On the LAN side of your router there are three possibilities:

  • Routable IPv4 addresses (unlikely)
  • Non-routable IPv4 addresses (and NAT)
  • Only IPv4 addresses (and NAT64)

Unless you are using routable IPv4 addresses on the LAN side of your router, there are 5 possibilities on the WAN side of your router:

  • Routable IPv4 address (this is what most ISPs used to do)
  • Non-routable IPv4 address (and CGN)
  • NAT64
  • DS-Lite
  • 4rd

Knowing which of the 11 possible combinations the ISP intended you to use would help debugging the issue. The first thing you need to verify is whether you got both an IPv4 and an IPv6 address on your network interface, or if you got only one of them.

There are a few obvious possibilities for what might be going wrong.

If you find the menu called Edit Connections... you can choose whether IPv4 is required on the connection and whether IPv6 is required on the connection. If neither is checked it would require at least one of the two to work in order to consider the connection healthy.

Next if NAT64 is involved, then you also need DNS64. If the ISP intend you to use NAT64, they will also provide you a DNS server with DNS64. But if you opt to use a different DNS server you will (most likely) not get DNS64.

If your ISP intend you to use NAT64 but you do not want to use the ISP provided DNS servers, you can still use a different DNS server, but it has to be configured with DNS64 and the same prefix as the NAT64 provided by your ISP.

If the LAN is using non-routable IPv4 addresses and the WAN is using NAT64, your router need to support NAT464. NAT464 need to know the prefix used by NAT64, usually it finds that prefix by querying the DNS server for a name which is resolved using DNS64. It is technically possible for a NAT464 implementation to support static configuration of the NAT64 prefix, which eliminates the need for DNS64.

Settings which may help

In short the following settings may be related to the problem:

  • Require IPv4 addressing for this connection to complete
  • Require IPv6 addressing for this connection to complete
  • DNS Servers

If proper settings for those is not enough to solve the problem, then you need to find more information in order to get a better answer.

Improve this answer
2
  • Thanks for your help! For some reason, the router is in a good mood today and gave me IPv4. I know how frustrating it is when something breaks and works again without understanding, but I am confident that it will randomly break again in the next few months or so, so just be patient and I'll be back.
    – Simon Kuang
    Commented Jul 21, 2015 at 16:31
  • @SimonKuang While it is working you need to figure out what sort of NAT (if any) it is using. Knowing that will make it easier to figure out what went wrong, if it breaks again.
    – kasperd
    Commented Jul 21, 2015 at 20:30

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .