Networking Trivia

The essence of computer networking can only be realized through practical observations.I've made it a point to publish the methods for accessing network information from a host. For, eg. we were recently taught about the resource records that a name server maintains for mapping a domain name to its IP address.
Well you can always view the records, from a UNIX terminal using the host command."host" is a simple utility for performing DNS lookups.For more information on the "host" utility try the manual pages for host by typing "man host" on your terminal.

Observation: (Open the terminal/shell on your Linux distribution)

tanm@tanm-desktop:~$ host -v www.gmail.com

Trying "www.gmail.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48667
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 6, ADDITIONAL: 0

;; QUESTION SECTION:
;www.gmail.com. IN A

;; ANSWER SECTION:
www.gmail.com. 74714 IN CNAME mail.google.com.
mail.google.com. 593108 IN CNAME googlemail.l.google.com.
googlemail.l.google.com. 10 IN A 74.125.157.19
googlemail.l.google.com. 10 IN A 74.125.157.83
googlemail.l.google.com. 10 IN A 74.125.157.17
googlemail.l.google.com. 10 IN A 74.125.157.18

;; AUTHORITY SECTION:
l.google.com. 74708 IN NS e.l.google.com.
l.google.com. 74708 IN NS f.l.google.com.
l.google.com. 74708 IN NS g.l.google.com.
l.google.com. 74708 IN NS a.l.google.com.
l.google.com. 74708 IN NS b.l.google.com.
l.google.com. 74708 IN NS d.l.google.com.

Received 244 bytes from 218.248.255.161#53 in 12 ms
Trying "googlemail.l.google.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26791
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;googlemail.l.google.com. IN AAAA

;; AUTHORITY SECTION:
l.google.com. 421 IN SOA a.l.google.com. dns-admin.google.com. 1392178 900 900 1800 60

Received 89 bytes from 218.248.255.161#53 in 17 ms
Trying "googlemail.l.google.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 51967
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;googlemail.l.google.com. IN MX

;; AUTHORITY SECTION:
l.google.com. 60 IN SOA b.l.google.com. dns-admin.google.com. 1392178 900 900 1800 60

Received 89 bytes from 218.248.255.161#53 in 308 ms

What you get to see here are the alias name that gmail uses. Moreover this might also help you to get the alternative server address for gmail, if their default server is down. There is more to be explored using this utility. Shall keep updating them as and when they work for me.