Già nel seguente articolo avevamo affrontato il funzionamento di nslookup:
Ecco invece alcuni esempi ripresi dal seguente articolo:
Se invece vogliamo usare il comando DIG possiamo guardare il seguente articolo che con 10 esempi spiega il tutto:
1. Query record A del DNS
$ nslookup redhat.com Server: 192.168.19.2 Address: 192.168.19.2#53 Non-authoritative answer: Name: redhat.com Address: 209.132.183.181
2. Query Record MX
$ nslookup -query=mx redhat.com Server: 192.168.19.2 Address: 192.168.19.2#53 Non-authoritative answer: redhat.com mail exchanger = 10 mx2.redhat.com. redhat.com mail exchanger = 5 mx1.redhat.com. Authoritative answers can be found from: mx2.redhat.com internet address = 66.187.233.33 mx1.redhat.com internet address = 209.132.183.28
La differenza fra autorativo e non autorativo è spiegata bene qua:
"Any answer that originates from the DNS Server which has the complete zone file information available for the domain is said to be authoritative answer.
In many cases, DNS servers will not have the complete zone file information available for a given domain. Instead, it maintains a cache file which has the results of all queries performed in the past for which it has gotten authoritative response. When a DNS query is given, it searches the cache file, and return the information available as “Non-Authoritative Answer”."
3. Query dell'NS Record
il record NS è quello che indica qual'è il DNS che è autorativo per quel dominio
nslookup -type=ns redhat.com Server: 192.168.19.2 Address: 192.168.19.2#53 Non-authoritative answer: redhat.com nameserver = ns4.redhat.com. redhat.com nameserver = ns2.redhat.com. redhat.com nameserver = ns1.redhat.com. redhat.com nameserver = ns3.redhat.com. Authoritative answers can be found from: ns4.redhat.com internet address = 209.132.188.218 ns2.redhat.com internet address = 209.132.183.2 ns1.redhat.com internet address = 209.132.186.218 ns3.redhat.com internet address = 209.132.176.100
4. Query dell'SOA Record
Il SOA Record da informazione autorative del dominio, email adress, domain admins, serial number del dominio....
$ nslookup -type=soa redhat.com Server: 192.168.19.2 Address: 192.168.19.2#53 Non-authoritative answer: redhat.com origin = ns1.redhat.com mail addr = noc.redhat.com serial = 2012071601 refresh = 300 retry = 180 expire = 604800 minimum = 14400 Authoritative answers can be found from: ns1.redhat.com internet address = 209.132.186.218
Ecco la descrizione:
"mail addr – specifies the mail address of the domain admin ( noc@redhat.com )
- serial – sort of revision numbering system. The standard convention is to use “YYYYMMYYNN” format. ( 2012-07-16. 01 will be incremented, if more than one edit has taken place on a same day )
- refresh – specifies ( in seconds ), when the secondary DNS will poll the primary to see if the serial number has been increased. If increased, secondary will make a new request to copy the new zone file.
- retry – specifies the interval to re-connect with the Primary DNS
- expire – specifies the time that the secondary DNS will keep the cached zone file as valid
- minimum – specifies the time that the secondary DNS should cache the zone file"
5. Fare la - query=any
$ nslookup -type=any google.com Server: 192.168.19.2 Address: 192.168.19.2#53 Non-authoritative answer: Name: google.com Address: 173.194.35.7 Name: google.com Address: 173.194.35.8 google.com nameserver = ns1.google.com. google.com nameserver = ns2.google.com. google.com origin = ns1.google.com mail addr = dns-admin.google.com serial = 2012071701 refresh = 7200 retry = 1800 expire = 1209600 minimum = 300 google.com mail exchanger = 20 alt1.aspmx.l.google.com. google.com mail exchanger = 30 alt2.aspmx.l.google.com. google.com mail exchanger = 40 alt3.aspmx.l.google.com. google.com mail exchanger = 50 alt4.aspmx.l.google.com. google.com mail exchanger = 10 aspmx-v4v6.l.google.com. google.com has AAAA address 2a00:1450:4002:801::1004 Authoritative answers can be found from: ns4.google.com internet address = 216.239.38.10 ns3.google.com internet address = 216.239.36.10
6. Si può fare anche il REVERSE Lookup
$ nslookup 209.132.183.181 Server: 192.168.19.2 Address: 192.168.19.2#53 Non-authoritative answer: 181.183.132.209.in-addr.arpa name = origin-www2.redhat.com.
7. Se vogliamo fare le query DNS su un server DNS alternativo
$ nslookup redhat.com ns1.redhat.com Server: 209.132.186.218 Address: 209.132.186.218#53 Name: redhat.com Address: 209.132.183.181
8. Cambiare la porta dove sta in listening il DNS
Se il DNS non lavora sulla porta standard ma su una diversa:
$ nslookup -port 112 redhat.com
9. Cambiare il timeout di risposta del DNS alle nostre query
$ nslookup -timeout=10 redhat.com
10. Effettuare il debug dns
$ nslookup -debug redhat.com
Server: 192.168.19.2
Address: 192.168.19.2#53
------------
QUESTIONS:
redhat.com, type = A, class = IN
ANSWERS:
-> redhat.com
internet address = 209.132.183.181
ttl = 5
AUTHORITY RECORDS:
ADDITIONAL RECORDS:
------------
Non-authoritative answer:
Name: redhat.com
Address: 209.132.183.181
