In this problem, we use the useful dig tool available on Unix and Linux hosts to
ID: 2247989 • Letter: I
Question
In this problem, we use the useful dig tool available on Unix and Linux hosts to explore the hierarchy of DNS servers. Recall that in Figure 2.19, a DNS server in the DNS hierarchy delegates a DNS query to a DNS server lower in the hierarchy, by sending back to the DNS client the name of that lower-level DNS server. First read the man page for dig, and then answer the following questions. a. Starting with a root DNS server (from one of the root servers [a-m]. root-servers.net), initiate a sequence of queries for the IP address for your department's Web server by using dig. Show the list of the names of DNS servers in the delegation chain in answering your query. b. Repeat part (a) for several popular Web sites, such as google.com, yahoo .com, or amazon.com.Explanation / Answer
The dig tool will allow the user to get the information about (a) IP address (b) text annotations (c) nameservers and (d) mail exchanges.
The symbol 'A' is used for the address "MX" is used for mail servers, "NS" is used for authoritative DNS servers, and the word ANY is used to get set of all the information.
+trace is used for tracing of path taken
answer (A)
<<>> DiG 9.9.5-3ubuntu0.16-Ubuntu <<>> any cse.iith.ac.in
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16450
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 1, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;cse.iith.ac.in. IN ANY
;; ANSWER SECTION:
cse.iith.ac.in. 76855 IN NS dns2.iith.ac.in.
cse.iith.ac.in. 76855 IN A 218.248.6.135
;; AUTHORITY SECTION:
cse.iith.ac.in. 76855 IN NS dns2.iith.ac.in.
;; Query time: 31 msec
;; SERVER: 127.0.1.1#53(127.0.1.1)
;; WHEN: Wed Sep 20 12:54:23 IST 2017
;; MSG SIZE rcvd: 92
answer (b)
dig for google.com
<>> DiG 9.9.5-3ubuntu0.16-Ubuntu <<>> any google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 38758
;; flags: qr rd ra; QUERY: 1, ANSWER: 11, AUTHORITY: 4, ADDITIONAL: 15
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;google.com. IN ANY
;; ANSWER SECTION:
google.com. 563 IN MX 10 aspmx.l.google.com.
google.com. 563 IN MX 20 alt1.aspmx.l.google.com.
google.com. 563 IN MX 50 alt4.aspmx.l.google.com.
google.com. 563 IN MX 40 alt3.aspmx.l.google.com.
google.com. 563 IN MX 30 alt2.aspmx.l.google.com.
google.com. 50 IN AAAA 2404:6800:4007:800::200e
google.com. 49 IN A 216.58.197.78
google.com. 73953 IN NS ns4.google.com.
google.com. 73953 IN NS ns2.google.com.
google.com. 73953 IN NS ns1.google.com.
google.com. 73953 IN NS ns3.google.com.
;; AUTHORITY SECTION:
google.com. 73953 IN NS ns1.google.com.
google.com. 73953 IN NS ns2.google.com.
google.com. 73953 IN NS ns4.google.com.
google.com. 73953 IN NS ns3.google.com.
;; ADDITIONAL SECTION:
ASPMX.l.google.com. 234 IN A 74.125.200.27
ALT1.ASPMX.l.google.com. 159 IN A 74.125.28.26
alt2.ASPMX.l.google.com. 234 IN A 74.125.198.26
alt3.ASPMX.l.google.com. 234 IN A 74.125.69.26
alt4.ASPMX.l.google.com. 235 IN A 173.194.219.26
ns1.google.com. 246795 IN A 216.239.32.10
ns2.google.com. 246795 IN A 216.239.34.10
ns3.google.com. 246795 IN A 216.239.36.10
ns4.google.com. 246795 IN A 216.239.38.10
ASPMX.l.google.com. 256 IN AAAA 2404:6800:4003:c02::1b
ALT1.ASPMX.l.google.com. 256 IN AAAA 2607:f8b0:400e:c04::1a
alt2.ASPMX.l.google.com. 256 IN AAAA 2607:f8b0:4003:c05::1a
alt3.ASPMX.l.google.com. 256 IN AAAA 2607:f8b0:4001:c08::1a
alt4.ASPMX.l.google.com. 256 IN AAAA 2607:f8b0:4002:c03::1a
;; Query time: 31 msec
;; SERVER: 127.0.1.1#53(127.0.1.1)
;; WHEN: Wed Sep 20 12:36:01 IST 2017
;; MSG SIZE rcvd: 629
amazon.com
; <<>> DiG 9.9.5-3ubuntu0.16-Ubuntu <<>> any amazon.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 51324
;; flags: qr rd ra; QUERY: 1, ANSWER: 12, AUTHORITY: 6, ADDITIONAL: 9
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;amazon.com. IN ANY
;; ANSWER SECTION:
amazon.com. 4 IN A 54.239.17.7
amazon.com. 4 IN A 54.239.25.200
amazon.com. 4 IN A 54.239.26.128
amazon.com. 4 IN A 54.239.17.6
amazon.com. 4 IN A 54.239.25.208
amazon.com. 4 IN A 54.239.25.192
amazon.com. 2531 IN NS pdns1.ultradns.net.
amazon.com. 2531 IN NS ns1.p31.dynect.net.
amazon.com. 2531 IN NS ns4.p31.dynect.net.
amazon.com. 2531 IN NS pdns6.ultradns.co.uk.
amazon.com. 2531 IN NS ns3.p31.dynect.net.
amazon.com. 2531 IN NS ns2.p31.dynect.net.
;; AUTHORITY SECTION:
amazon.com. 2531 IN NS ns2.p31.dynect.net.
amazon.com. 2531 IN NS ns3.p31.dynect.net.
amazon.com. 2531 IN NS ns1.p31.dynect.net.
amazon.com. 2531 IN NS pdns6.ultradns.co.uk.
amazon.com. 2531 IN NS ns4.p31.dynect.net.
amazon.com. 2531 IN NS pdns1.ultradns.net.
;; ADDITIONAL SECTION:
ns1.p31.dynect.net. 73261 IN A 208.78.70.31
ns2.p31.dynect.net. 73261 IN A 204.13.250.31
ns3.p31.dynect.net. 73253 IN A 208.78.71.31
ns4.p31.dynect.net. 73237 IN A 204.13.251.31
pdns1.ultradns.net. 2022 IN A 204.74.108.1
pdns6.ultradns.co.uk. 2807 IN A 204.74.115.1
pdns1.ultradns.net. 2022 IN AAAA 2001:502:f3ff::1
pdns6.ultradns.co.uk. 2807 IN AAAA 2610:a1:1017::1
;; Query time: 31 msec
;; SERVER: 127.0.1.1#53(127.0.1.1)
;; WHEN: Wed Sep 20 12:48:36 IST 2017
;; MSG SIZE rcvd: 520
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