Skip to main content

nslookup Command

A Network Administrator command  which help diagnosis DNS related issue. However to understand this,  you should better to know how DNS works.

How to troubleshoot DNS related issue.

1. NSLOOKUP example display "A Record" (IP Adress) of the domain




C:\Users\jpudasaini>nslookup jpudasaini.com.np 8.8.8.8
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

Non-authoritative answer:
Name:    jpudasaini.com.np
Address:  216.239.32.21

A Non-Authoritative Answer is a response from Cache. A DNS server is
authoritative for zones actually holds it.

The above output shows "A Records" (IP Adress) of the domain
"jpudasaini.com.np". Which is actually query to the public Google DNS. If
you don't put DNS after the domain, it will used your default DNS, in my
case I have used public DNS.

2. MX Record using -query=mx

MX (Mail Exchange) record maps for the specific domain name to verify mail
exchaing servers on that domain.


C:\Users\jpudasaini>nslookup -query=mx gmail.com 8.8.8.8
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

Non-authoritative answer:
gmail.com       MX preference = 40, mail exchanger =alt4.gmail-smtp-in.l.google
.com
gmail.com       MX preference = 20, mail exchanger =alt2.gmail-smtp-in.l.google
.com
gmail.com       MX preference = 10, mail exchanger =alt1.gmail-smtp-in.l.google
.com
gmail.com       MX preference = 30, mail exchanger =alt3.gmail-smtp-in.l.google
.com
gmail.com       MX preference = 5, mail exchanger =gmail-smtp-in.l.google.com

From the above example we can say that  4 MX records used for gmail
domain, the number associat with mx reference the preference of mail
server. Lower the number, higher the preference. So
gmail-smtp-in.l.google.com is the first server which received the mail at
first.

3. NS Record using -query=ns

NS (Name Server) records maps a domain to a list of DNS servers
authoritative for that domain. Here is example of name server which are
associated with jpudasaini.com.np doamain.

C:\Users\jpudasaini>nslookup -query=ns jpudasaini.com.np 8.8.8.8
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

Non-authoritative answer:
jpudasaini.com.np       nameserver = ns4.afraid.org
jpudasaini.com.np       nameserver = ns2.afraid.org
jpudasaini.com.np       nameserver = ns1.afraid.org

4. SOA Record using -query=soa

 C:\Users\jpudasaini>nslookup -query=soa jpudasaini.com.np 8.8.8.8
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

Non-authoritative answer:
jpudasaini.com.np
        primary name server = ns1.afraid.org
        responsible mail addr = dnsadmin.afraid.org
        serial  = 1511030001
        refresh = 86400 (1 day)
        retry   = 7200 (2 hours)
        expire  = 2419200 (28 days)
        default TTL = 3600 (1 hour)

SOA record (start of authority) which provides the authoritative
information, as well as e-mail address, serial no of the respective
domain.


5. Reserve DNS lookup

The reverse DNS look-up using IP Adress as argument to nslookup
C:\Users\jpudasaini>nslookup 216.239.32.21 8.8.8.8
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

Name:    any-in-2015.1e100.net
Address:  216.239.32.21


6. Using Specific DNS Server

Make query using particular name server instead of using default DNS server.


C:\Users\jpudasaini>nslookup jpudasaini.com.np ns1.afraid.org
Server:  UnKnown
Address:  50.23.197.95

Name:    jpudasaini.com.np
Address:  216.239.32.21

Comments

Popular posts from this blog

Unable to open kernel device . global vmx86 windows 7

Suddenly I encounter a weird problem with VMware 9 version. I install different OS for my education and testing purposed. Like MAC os, Ubuntu, CentOS, BT, WinXP, Win-server 2003. When I tried to run one of this OS a error message appear. unable to open kernel device "\\.Global\vmx86": The system cannot find the file specified. Did you reboot after installing VMware Workstation? Failed to initialize monitor device. Click ok you can see this window After googling I found one solution in developer forum but thread starter never use that method. So I tried it and here is my finding. Go to the directory of vmware installed  (In my case I run it as Administrator) C:\Program Files (x86)\VMware\VMware Workstation>   ( I've 32-bit apps on 64-bit OS, your may be different) Run this command vnetlib -- uninstall vmx86  reboot Go to the same directory and check net start command - this time it should say "service name  is invalid&quo

Simple Failover Mikrotik

Simple fail-over Mikrotik router configuration. Most of the user wants backup link (Fiber link with Wireless backup), in case fiber down wireless link auto up. No downtime for the user. Here is simple setting on Mikrotik for fail-over. I'm very great full to Anton to point out the mistake in src-address. It has been corrected now. ****default routes for new outgoing traffic.**** /ip route add dst-address=0.0.0.0/0 gateway=ISP-GW-ADDR-1 distance=1 check-gateway=ping add dst-address=0.0.0.0/0 gateway=ISP-GW-ADDR-2 distance=2 ++masquerade both WAN connections++ /ip firewall nat add chain=srcnat src-address=192.168.0.0/24 out-interface=WAN-1 action=masquerade add chain=srcnat src-address=192.168.0.0/24 out-interface=WAN-2 action=masquerade Thats it.

Mikrotik Hotspot Redirect After Login

This tutorial assumed you already create Hotspot in your router. If you don't know how to create a hotspot in Mikrotik router, click here and create the Hotspot. . After successfully creating the hotspot server go to "Files" Menu of  the main Window of Mikrotik router Copy "hotspot" folder into your PC. Open "alogin" file with text editor Replace "link-redirect" text with your desire URL Now you're done! After successfully logging into the Hotspot server your client automatically redirects to your external link.  Don't forget to copy this folder into Mikrotik Router "Files" Menu. You can also drag and drop this folder into "Files" menu.