You should switch to better learning material... Taking a look at the very basic syntax of nslookup
command line parameters (shown below) your 2nd example is asking to find the IP address of mail.yahoo.com
using a DNS server gatech.edu
. As the latter probably isn't responding to your request, you get a timeout.
nslookup [-option] [name | -] [server]
As for the possible reasons for the failure, there are several.
Possible reason 1:
As I noted above, gatech.edu
is not probably resolving to the IP address of a DNS server.
I took a look at the DNS records of the mentioned domain:
C:\>nslookup
> gatech.edu
Server: server.example.com
Address: xxx.xxx.xxx.xxx
Non-authoritative answer:
Name: gatech.edu
Address: 130.207.160.173
> set q=ns
> gatech.edu
Server: server.example.com
Address: xxx.xxx.xxx.xxx
Non-authoritative answer:
gatech.edu nameserver = dns3.gatech.edu
gatech.edu nameserver = dns1.gatech.edu
gatech.edu nameserver = dns2.gatech.edu
dns3.gatech.edu internet address = 168.24.2.35
dns1.gatech.edu internet address = 128.61.244.253
dns1.gatech.edu AAAA IPv6 address = 2610:148:1f00:f400::3
dns2.gatech.edu internet address = 130.207.244.81
dns2.gatech.edu AAAA IPv6 address = 2610:148:1f01:f400::3
So, gatech.edu
resolves to 130.207.160.173
(the 1st query), but the (main) DNS servers for the domain (2nd query) have different IPs.
Possible reason 2:
As @netniV pointed out in his comment, there might be a firewall restriction that is denying DNS resolution from other sources than whatever is the preferred DNS server for the domain you're in.
2
What learning material you are using in your learning? Taking a look at the very basic syntax of
– zagrimsan – 2015-09-28T09:49:59.343nslookup
command line parameters your 2nd example is asking to find the IP address ofmail.yahoo.com
using a DNS servergatech.edu
. As the latter probably isn't responding to your request, you get a timeout.1@zagrimsan this should be an answer :) – Jonas Köritz – 2015-09-28T10:11:27.213