Set DNS Servers For All Wifi Networks

[Tommy Trussell]

On Wed, Sep 10, 2014 at 3:42 PM, Sajan Parikh <sajan at parikh.io> wrote:

> On 09/10/2014 02:56 PM, Colin Law wrote:
>
>> On 10 September 2014 20:42, Sajan Parikh <sajan at parikh.io> wrote:
>>
>>> Right now, I can go into the connection manager, choose a wireless
>>> network
>>> and update the DNS servers to use by setting the IPv4 to Automatic DHCP,
>>> address only.  However, when I connect to another network, the default
>>> is to
>>> pull an IP address from the DHCP along with the DNS servers.
>>>
>>> Is there a way for me to default all new connections to DHCP Address
>>> Only,
>>> and set some sort of permanent DNS servers?  I thought about throwing
>>> them
>>> into /etc/resolv.conf, but I assume that gets overwritten everytime I
>>> switch
>>> connections.
>>>
>> I cannot help with the problem but would be interested to know why one
>> would want to use specific DN Servers.
>>
>> Colin
>>
>>  Hotel networks, sometimes libraries, and even some coffee shops whose
> networks are configured by smaller, local ISPs have caused me issues
> multiple times over the past few weeks while traveling.
>
> Some DNS records that I absolutely know should resolve, don't.  The last
> time I had this issue was at a hotel, and I ran dig +trace
> host.thatshoud.resolve and saw some message about some limit being
> reached.  Thought it was incredibly weird.  Edited my resolvers to Google,
> and it worked great of course.
>
> I don't know why that would happen, probably some upstream rate limiting,
> and I've never encountered this before the past 2 months. During which I've
> had this same exact issue at 5 different networks.
>
> *Yes, the records that don't resolve are being served by my own DNS
> cluster, but that is all working properly and the dig trace I ran showed
> the error well before anything was queried to one of my servers.
>
> Sajan Parikh
>
>
It sounds to me like you may be seeing effects of the Internet outages that
started in August due to the number of Internet addresses in the world
exceeding the space available in older routers.

http://arstechnica.com/security/2014/08/internet-routers-hitting-512k-limit-some-become-unreliable/

http://en.wikipedia.org/wiki/512k_day

My understanding is that Cisco has been warning about the impending
failures for months

http://blogs.cisco.com/sp/global-internet-routing-table-reaches-512k-milestone/

but until some major sites went down starting August 12th, many
less-informed network people were unaware of the looming problem. The
issues are being resolved (for now) by Internet Service Providers
installing newer hardware and newer operating systems for their routers.

If this is the error you're seeing, there's nothing you can do other than
(as you have) trying a different DNS server and hoping the varying ISPs
between you and the sites you're accessing are updating their routers. In
other words, if this is the problem you're seeing, the problem isn't with
Ubuntu, it's with Internet hardware outside your control.
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