DNS problems this morning -

[Bob Goodwin - Zuni, Virginia, USA]

On 12/11/12 06:09, Tim wrote:
> Tim:
>>> > > Configure the other computers on your LAN to use the DNS server
>>> > > computer's IP address as their DNS server.  It's as simple as that.
> Bob Goodwin:
>> > Will dns look-ups from the other computers be added to the
>> > nameserver list?
> You appear to have the wrong end of the stick.
>
> When any client on your LAN asks your DNS server for an address, the DNS
> server makes a query to external DNS servers, caches the results, and
> tells your client the answer.  The next client on your LAN to ask about
> the same address, will be told the cached answer.
>
> Telling your clients which DNS server to use is another matter.
>
>> > What if my computer is shut down for the night, will the others go
>> > on and use the ISP dns?
> If you had, say your DNS server at 192.168.0.1, and clients configured
> to only use 192.168.0.1 as their DNS server, then they're reliant on
> 192.168.0.1 always being there.
>
> If you had configured your clients with a list of DNS servers, they'll
> query one of them, only trying other ones when they don't get any
> response.  I don't know what determines which DNS server will get
> queried out of a list, whether Fedora will do it sequentially down the
> list, or randomly.  Nor whether any subsequent queries will use the same
> server as the last time, or pick another one each time.

    I always naively assumed they were used in the order listed, now you've
    introduced an element of doubt, nothing is ever simple it seems. If
    it was I
    could give others the local and then the outside dns addresses, but
    no that may
    not work as expected. I suppose I could test that scheme using two
    of my computers,
    one getting dns service from the other and see what happened when I
    shut down the dns
    of the pair.

>
>>> > > The complications are:  If your other computers are assigned addresses
>>> > > by DHCP, then you have to put overrides on the individual client
>>> > > configuration, or configure the DHCP server to say that *YOUR* DNS
>>> > > server is the LAN's DNS server to all computers that ask it for an
>>> > > address (I do this with mine).
>> > DHCP via the router was the path of least resistance, they get
>> > static assignments, but I could set them up with fixed addresses if
>> > that is necessary. I used to do that but the present set-up is
>> > easier to implement and normally works perfectly.
> They don't need to be fixed, your DNS server will not care what IP they
> have today, or tomorrow.  My LAN has a mixture of clients with fixed and
> dynamic addresses, some are fixed by hand configuring those machine's
> network configuration, on those machines.  Others are fixed by
> configuring the DHCP server to always give the same IPs to the same
> machines.
>
> In any case, they all use the same DNS server.  The manually configured
> machines had the local DNS server manually set in their config.  All the
> rest were told to use the local DNS server in the data that the local
> DHCP server gives out.

    Whatever the problem yesterday it seems to be fixed today. The ISP
    dns appears
    to be working normally. However I am still interested in doing
    anything that
    improves operation.


"Was it you that we had this discussion with before? I can never 
remember who's
doing what in threads, especially old or long-lasting ones."

    Yes I had a similar problem affecting access to Newegg's site and
    they thought it
    was their problem? That was when I discovered I could no longer use
    Opendns.

    I read somewhere that the ISP does this as a result of some caching
    they do to reduce
    traffic through the satellite link. That seemed plausible ...

    Bob

-- 
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box7