bind-users Digest, Vol 2230, Issue 1
Harshith Mulky
harshith.mulky at outlook.com
Tue Oct 20 14:49:45 UTC 2015
No Mark, This is not a question I am asked to answer for some course
We have an implementation where, once the DNS Servers are down, The Client (Our device) Blacklists the IP address of DNS Servers for some period of Time
It can only whitelist the server when it receives periodic Responses to a NAPTR Request.
What I did find was even though Our Client was able to send periodic NAPTR requests, we are unable to check what kind of NAPTR requests are sent out
Hence my question,
What Kind of messages are required by the client to be sent towards server to determine if the DNS IP is reachable or not?
Thanks
Harshith
> From: bind-users-request at lists.isc.org
> Subject: bind-users Digest, Vol 2230, Issue 1
> To: bind-users at lists.isc.org
> Date: Tue, 20 Oct 2015 12:00:01 +0000
>
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> Today's Topics:
>
> 1. How does a Client Verify if the DNS server is Alive or down
> (Harshith Mulky)
> 2. Re: How does a Client Verify if the DNS server is Alive or
> down (Matus UHLAR - fantomas)
> 3. Re: How does a Client Verify if the DNS server is Alive or
> down (Wah Peng)
> 4. Re: How does a Client Verify if the DNS server is Alive or
> down (Mark Andrews)
> 5. Re: How does a Client Verify if the DNS server is Alive or
> down (Phil Mayers)
> 6. Re: How does a Client Verify if the DNS server is Alive or
> down (Steven Carr)
> 7. Re: How does a Client Verify if the DNS server is Alive or
> down (Reindl Harald)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 20 Oct 2015 11:56:54 +0530
> From: Harshith Mulky <harshith.mulky at outlook.com>
> To: "bind-users at lists.isc.org" <bind-users at lists.isc.org>
> Subject: How does a Client Verify if the DNS server is Alive or down
> Message-ID: <BLU184-W39A0F214A762089BF7B23B81390 at phx.gbl>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi All,
>
> How can a Client verify if the DNS Server is Running(named service is Running) or Down?
> Does it periodically send any messages to the server. What Kind of messages are required by the client to be sent towards server to determine if the DNS IP is reachable or not?
>
> Thanks
> Harshith
>
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> ------------------------------
>
> Message: 2
> Date: Tue, 20 Oct 2015 08:42:04 +0200
> From: Matus UHLAR - fantomas <uhlar at fantomas.sk>
> To: bind-users at lists.isc.org
> Subject: Re: How does a Client Verify if the DNS server is Alive or
> down
> Message-ID: <20151020064204.GA13681 at fantomas.sk>
> Content-Type: text/plain; charset=us-ascii; format=flowed
>
> On 20.10.15 11:56, Harshith Mulky wrote:
> >How can a Client verify if the DNS Server is Running(named service is Running) or Down?
>
> Why should client know such info?
> The clients needs to have the answer - it sends message and if the server
> replies properly, it's up and running.
>
> >Does it periodically send any messages to the server. What Kind of messages
> > are required by the client to be sent towards server to determine if the
> > DNS IP is reachable or not?
>
> what is your problem?
>
> --
> Matus UHLAR - fantomas, uhlar at fantomas.sk ; http://www.fantomas.sk/
> Warning: I wish NOT to receive e-mail advertising to this address.
> Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
> Remember half the people you know are below average.
>
>
> ------------------------------
>
> Message: 3
> Date: Tue, 20 Oct 2015 14:50:00 +0800
> From: Wah Peng <wah_peng at yahoo.com.sg>
> To: bind-users at lists.isc.org
> Subject: Re: How does a Client Verify if the DNS server is Alive or
> down
> Message-ID: <5625E418.9050106 at yahoo.com.sg>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> Hello,
>
> Network issue should be detected by other ways.
> But DNS health check can be done by sending a normal DNS query to the
> server and try get a valid response.
>
> This is the script what I use to check the health of my DNS server. :D
>
> #!/usr/bin/perl
> use strict;
> use Net::DNS;
> use POSIX 'strftime';
> use MIME::Lite;
> use MIME::Words qw(encode_mimewords);
>
> my $debug = 0;
> my $test_rr = 'alive.example.net';
> my $test_val = '8.8.8.8';
> my @nameservers = qw(1.1.1.1 2.2.2.2);
>
> for my $ns (@nameservers) {
> test_query($ns);
> }
>
> sub test_query {
> my $ns = shift;
> my $res = Net::DNS::Resolver->new(nameservers => [$ns]);
> $res->tcp_timeout(10);
> $res->udp_timeout(10);
> my $answer = $res->query($test_rr);
>
> if (defined $answer) {
> my @rr = $answer->answer;
> if ($rr[0]->address ne $test_val) {
> sendmail( "DNS not matched: $ns" );
> print "$ns wrong\n";
> }
> if ($debug) {
> print "$ns expected value for $test_rr: $test_val\n";
> print "$ns got value for $test_rr: ", $rr[0]->address,"\n";
> }
> } else {
> sendmail( "Can't query to: $ns" );
> print "$ns wrong\n";
> }
> }
>
>
> sub sendmail {
> # your email function to send the alerts
> }
>
> Regards.
>
>
> On 2015/10/20 ??? 14:26, Harshith Mulky wrote:
> > How can a Client verify if the DNS Server is Running(named service is
> > Running) or Down?
> > Does it periodically send any messages to the server. What Kind of
> > messages are required by the client to be sent towards server to
> > determine if the DNS IP is reachable or not?
>
>
> ------------------------------
>
> Message: 4
> Date: Tue, 20 Oct 2015 17:51:52 +1100
> From: Mark Andrews <marka at isc.org>
> To: bind-users at isc.org
> Subject: Re: How does a Client Verify if the DNS server is Alive or
> down
> Message-ID: <20151020065152.BFE313ACF367 at rock.dv.isc.org>
>
>
> In message <20151020064204.GA13681 at fantomas.sk>, Matus UHLAR - fantomas writes:
> > On 20.10.15 11:56, Harshith Mulky wrote:
> > >How can a Client verify if the DNS Server is Running(named service is Runnin
> > g) or Down?
> >
> > Why should client know such info?
> > The clients needs to have the answer - it sends message and if the server
> > replies properly, it's up and running.
> >
> > >Does it periodically send any messages to the server. What Kind of messages
> > > are required by the client to be sent towards server to determine if the
> > > DNS IP is reachable or not?
> >
> > what is your problem?
>
> My bet this a question from some course that Harshith has been
> requested to answer.
>
> Mark
> --
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742 INTERNET: marka at isc.org
>
>
> ------------------------------
>
> Message: 5
> Date: Tue, 20 Oct 2015 10:41:53 +0100
> From: Phil Mayers <p.mayers at imperial.ac.uk>
> To: bind-users at lists.isc.org
> Subject: Re: How does a Client Verify if the DNS server is Alive or
> down
> Message-ID: <56260C61.9070003 at imperial.ac.uk>
> Content-Type: text/plain; charset=windows-1252; format=flowed
>
> On 20/10/15 07:26, Harshith Mulky wrote:
> > Hi All,
> >
> > How can a Client verify if the DNS Server is Running(named service is
> > Running) or Down?
>
> By the presence or absence of a reply to a query.
>
> > Does it periodically send any messages to the server.
>
> No. It just sends a query when it has one, and waits for a reply; if it
> doesn't get one, it tries another DNS server (if it has one)
>
>
> ------------------------------
>
> Message: 6
> Date: Tue, 20 Oct 2015 12:26:34 +0100
> From: Steven Carr <sjcarr at gmail.com>
> To: bind-users <bind-users at lists.isc.org>
> Subject: Re: How does a Client Verify if the DNS server is Alive or
> down
> Message-ID:
> <CALMep06qUWmG8JoRLbey_HviXgzdK65O7hJ=1a_mKbVyu_RZ3Q at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> On 20 October 2015 at 10:41, Phil Mayers <p.mayers at imperial.ac.uk> wrote:
> > On 20/10/15 07:26, Harshith Mulky wrote:
> >>
> >> Hi All,
> >>
> >> How can a Client verify if the DNS Server is Running(named service is
> >> Running) or Down?
> >
> >
> > By the presence or absence of a reply to a query.
>
> That doesn't always verify if the server is running or not, your
> client might not be allowed to query it, in which case you may get a
> refused response, or it may just not respond to you at all.
>
> Steve
>
>
> ------------------------------
>
> Message: 7
> Date: Tue, 20 Oct 2015 13:31:16 +0200
> From: Reindl Harald <h.reindl at thelounge.net>
> To: bind-users at lists.isc.org
> Subject: Re: How does a Client Verify if the DNS server is Alive or
> down
> Message-ID: <56262604.3050605 at thelounge.net>
> Content-Type: text/plain; charset="windows-1252"; Format="flowed"
>
>
> Am 20.10.2015 um 13:26 schrieb Steven Carr:
> > On 20 October 2015 at 10:41, Phil Mayers <p.mayers at imperial.ac.uk> wrote:
> >> On 20/10/15 07:26, Harshith Mulky wrote:
> >>>
> >>> How can a Client verify if the DNS Server is Running(named service is
> >>> Running) or Down?
> >>
> >> By the presence or absence of a reply to a query.
> >
> > That doesn't always verify if the server is running or not, your
> > client might not be allowed to query it, in which case you may get a
> > refused response, or it may just not respond to you at all.
>
> and the client can distinct NXDOMAIN, REFUSED, no connection at all
>
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