DNS Exercise 1
--------------

===========
Preparation
===========

1. Log in using SSH/Putty/... to your RESOLVER machine:

  (i.e. for group 1, you would use resolv.grp1.dns.nsrc.org)

    $ ssh sysadm@resolv.grpXX.dns.nsrc.org

    *** PLEASE MAKE SURE YOU ARE LOGGED IN TO YOUR 'RESOLV' MACHINE, AND ***
                  *** NOT IN YOUR 'AUTH1' or 'AUTH2' ***
				  
2. On your RESOLVER machine, modify /etc/resolv.conf temporarily
   to point 10.10.0.241 for this exercise 
   
    $ sudo ee /etc/resolv.conf
or
    $ sudo vi /etc/resolv.conf

---- Before
search dns.nsrc.org
nameserver 10.10.0.230

---- After
search dns.nsrc.org
#nameserver 10.10.0.230
nameserver 10.10.0.241

===
DIG
===

1. Issue DNS queries using 'dig':

1a. Run each command, look for the ANSWER section and write down the result.
    Make a note the TTL as well.

Repeat the command. Is the TTL the same? Are the responses Authoritative?

                                        RESULT 1            RESULT 2
                                        --------            --------
    $ dig your-favorite-domain a
    $ dig www.google.com. a
    $ dig afnog.org. mx
    $ dig NonExistentDomain.sometld any
    $ dig tiscali.co.uk. txt
    $ dig www.afrinic.net aaaa
    $ dig ipv6.google.com aaaa

1b. Now send some queries to another caching server.

    (Run each of the following twice, and note the time in ms for each attempt)

    $ dig @8.8.8.8 news.bbc.co.uk. a
    $ dig @resolver1.opendns.com yahoo.com. a
    $ dig @<a server of your choice> <domain of your choice> a

    How long did it take each answer to be received? (on the first, and
    on the second lookup)

2. Reverse DNS lookups

    Now try some reverse DNS lookups.

    $ dig -x 10.10.X.1
    $ dig -x 10.10.X.2
    $ dig -x 10.10.X.3

    ... where X is an IP address in the range 1-25

    Repeat for an IP address of your choice, on the Internet

    Now try to lookup:

    $ dig 1.X.10.10.in-addr.arpa. PTR

    ... where X is in the range 1-25.

    What do you notice ?

    Let's try IPv6 now:

    $ dig -x 2001:42d0::200:2:1

    What are the differences you can observe in the results, between reverse
    DNS for IPv6 and IPv4 addresses ?

3. DNSSEC & EDNS0

    Try some of the queries above, this time add the "+noedns" option.
    (From dig 9.9, EDNS0 is set by default)

    For example:

    $ dig www.icann.org +noedns

    Notice the absence of OPT PSEUDOSECTION, at the top of the output ?

    What do you notice about the flags: section in the OPT section ?

    Let's explicitly enable the BUFSIZE option, but not EDNS0:

    $ dig www.icann.org +bufsize=1024

    Notice that EDNS is set automatically, and notice the udp: size section
    in the OPT pseudosection.

    Now, let's try and retrieve DNSSEC records:

    $ dig isoc.org DNSKEY
    $ dig www.isoc.org RRSIG

    And finally, let's ask the DNS servers to perform DNSSEC validation:

    $ dig www.isoc.org A +dnssec
    $ dig isoc.org NS +dnssec

    Do you notice a new field in the "flags:" section of the answer ?

    $ dig www.isoc.org A
    $ dig isoc.org NS

    Compare with doing dig WITHOUT the +dnssec option:

===
DOC
===

1. Install doc-2.2.3 package

    $ sudo pkg install doc
    Updating FreeBSD repository catalog...
    (wait for a moment)

    (pkg itself needs to be updated, so just answer 'y')

    (answer 'y' again to install doc-2.2.3)

2. Using 'doc' to validate domain structure:

   Run each command and note "Summary:" part of the output.
   Did you find any domains with "Warning" or "Error" ?

   NOTE: Each of these commands creates log.domainname in the current working
   directory, so please make sure you are under your home directory.

   $ doc domain-of-your-org
   $ doc some-subdomain-of-above
   $ doc ees.kyushu-u.ac.jp  (an example with error)

   If you find warning or error, check the content of the log file:

   $ less log.domainname

   Try to find what is the problem of the domain.

========
Clean-up
========

1. Revert the modification of /etc/resolv.conf
   
    $ sudo ee /etc/resolv.conf
or
    $ sudo vi /etc/resolv.conf

---- Before
search dns.nsrc.org
#nameserver 10.10.0.230
nameserver 10.10.0.241

---- After
search dns.nsrc.org
nameserver 10.10.0.230
#nameserver 10.10.0.241