I was doing ping with parameter -a, when i encountered something strange. here is what i did.
I got the ip address from above command as 18.104.22.168
Then i used the command :
ping -a 22.214.171.124
My understanding was ping will also give me host name because we are using parameter - a, it did give me host name as:
I performed ip look up using http://ip-lookup.net/?126.96.36.199
I found entry as:
Here is my question, when i clicked this link i was able to get to www.help.com ,thereby proving the ip address 188.8.131.52 is indeed mapped to www help.com. But when i moved the cursor over cnet.com" right after the period between lb and cnet in the link, i was directed to www.cnet.com.
They are two complete host name mapped to 184.108.40.206. How is it possible?
May be i am not reading the mapping " 220.127.116.11--- c13-ss-help-www-lb.cnet.com" properly
thanks and have a good weekend.
These are the DNS lookups for the entries you are asking about -
18.104.22.168.in-addr.arpa. PTR 300 c13-ss-help-www-lb.cnet.com.
www.help.com. CNAME 300 c13-ss-help-www-lb.cnet.com.
22.214.171.124.in-addr.arpa. PTR 300 c13-sha-stack2-netscaler2.cnet.com.
Note the second entry for www.help.com is a CNAME and not a PTR like the other 2. A CNAME or Canonical Name record is simply a way to map one DNS name to another so if you enter "www.help.com" then a DNS lookup is done and the response is c13-ss-help-www-lb.cnet.com. This response will then be looked up again to get an IP address ie. the first entry above will provide this.
So it's simply a way of having multiple "names" mapped to a DNS names eg. www.help.com, ftp.help.com, smtp.help.com could if you wanted all be mapped to c13-ss-help-www-lb.cnet.com. And that is why you are seeing multiple names mapped to the same IP.