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Re: Can't find the DNS Servers




On Wed 04 Oct 2017 at 18:14:12 (-0400), Gene Heskett wrote:
> On Wednesday 04 October 2017 14:35:25 David Wright wrote:
> 
> > On Wed 04 Oct 2017 at 13:21:02 (-0400), Greg Wooledge wrote:
> > > On Wed, Oct 04, 2017 at 11:59:04AM -0500, David Wright wrote:
> > > > On Wed 04 Oct 2017 at 09:11:37 (+0300), Reco wrote:
> > > > > A correct way to fix this is to "persuade" your DHCP server not
> > > > > to provide DNS information.
> > > > > Even more correct way is to force your DNS-at-DHCP to use
> > > > > 8.8.8.8 as forwarder DNS.
> > > > > Since it's unnaturally complex to do so in a consumer-grade
> > > > > routers, a hack is in order.
> > > >
> > > > But won't that send local host lookups to google which won't have
> > > > a clue?
> > >
> > > Which problem are we attempting to solve, exactly?  I seem to recall
> > > that the reported symptom was "I can't do apt-get update", which
> > > means the priority is getting real Internet DNS resolution working.
> >
> > "I can't even reach the other computers on my home network if I use
> > their names. IP addresses work OK." as well.
> >
> You probably could if you enter their addresses and names in 
> your /etc/hosts file, and you can run the identical /etc/hosts file on 
> every machine on your home network.

Yes, I do that. The OP is presumably used to not having to do that.

> If you have network-mangler installed and running, stop it and remove it 
> else you may have to make your /etc/resolv.conf into a normal file, make 
> the nameservers work, then chattr +i resolv.conf to keep n-m from 
> tearing down a working network.
> 
> It should, if your router runs something like dnsmasq, be sufficient to 
> point the nameserver entry in your resolv.conf at the router, which 
> will, if its internal lookups fail, forward the dns request to your 
> ISP's dns servers. That adds about 60 milliseconds to the ping time of 
> some site never visited before.

Yes, I do that. As stated below, there are no internal lookups,
but the router has google nameservers configured in place of its
downloading them from my ISP.

> > > If there's a need to add local area network hosts, then *after* the
> > > real Internet DNS is working, the OP can decide whether to add LAN
> > > hosts to /etc/hosts on each machine, or to set up a LAN DNS
> > > nameserver, and wrangle resolv.conf and/or DHCP to point to it. 
> > > (Many steps and details omitted here for simplicity's sake.)
> >
> > I'm obviously out of my league. I was under the impression that
> > everyone set up networking by working outwards from the loopback
> > interface to the universe, rather than the other way round.
> 
> Basically that is how it works.

Well, thank you. But this doesn't explain the paragraph above my comment.
I'm just trying to understand the suggestions being made by more
experienced folk here, like Reco and Greg.

I suppose the main things I don't understand are:
why set up the DNS to resolve externals' addresses before internals';
why send LAN DNS queries out to 8.8.8.8 before consulting the LAN's
own server; why, on a home network, set external servers (like
8.8.8.8) in all the hosts' resolv.conf if the router itself can pass
queries to them. After all, if the router's not up, then those
external servers are unreachable anyway.

> > > Which way the OP *should* go depends mostly on how many LAN hosts
> > > we're talking about.  Which way they *will* go... anyone's guess.
> 
> Your /etc/hosts file can have, IIRC, up to 253 ipv4 entries. And it still 
> is identical on all machines provided they all know their assigned 
> names.  Check that by running hostname w/o an argument. See man 
> hostname, ditto for domainname.

Um, I'm not sure what you're remembering.
$ wc /etc/hosts
 13263  27599 402246 /etc/hosts
$ 
I think there are limits on line length/aliases.

> > As I just posted, I thought the OP was already using a DNS server in
> > the Actiontec router. (I don't have that choice.)
> >
> Why not David?

Because I have a "plastic" router with a server for DHCP but not DNS.

> Get one that has enough memory to be reflashed with 
> dd-wrt, which will have that feature, and since its .de sourced, not at 
> all likely to have any back doors for the 3 letter agencies.

But why would I buy a wireless router that you don't trust enough
to have its wireless turned on?

If we spend money here, it'll be for a repeater and/or more
homeplug-style devices.

> Most routers in the $70+ category can do that. In way over a decade, only 
> one person has come thru dd-wrt and I had to give him all the usernames 
> and passwd's to do so. I needed his expertise at the time.
> 
> Buffalo sells several with dd-wrt already installed, but their branding 
> covered up a needed section of the setup, so I had to go get the real 
> thing from the dd-wrt site & install it.  Shrug.

Cheers,
David.