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Network Operating Systems-I

notes most small sites, but some e-commerce applications require matching entries to operate correctly.
You may have to ask your ISP to make a custom DNS change to correct this.
There are a number of commands you can use do these lookups. Linux uses the host command,
for example, but Windows uses nslookup.

The Host Command

The host command accepts arguments that are either the fully qualified domain name or the IP
address of the server when providing results. To carry out a forward lookup, use the syntax:
[root@bigboy tmp]# host www.Ignou.ac.in
www.Ignou.ac.in has address 220.227.168.115

[root@bigboy tmp]#
To perform a reverse lookup

[root@bigboy tmp]# host 220.227.168.115
34.71.115.65. in-addr.arpa domain name pointer 65-115-71-34.myisp.net.

[root@bigboy tmp]#
As you can see, the forward and reverse entries don’t match. The reverse entry matches the entry
of the ISP.

The nslookup Command

The nslookup command provides the same results on Windows PCs. To perform forward lookup,
use.
C:\> nslookup www.Ignou.ac.in
Server: 192-168-1-200.my-site.com
Address: 192.168.1.200

Non-authoritative answer:
Name: www.Ignou.ac.in
Address: 220.227.168.115
C :\>

to perform a reverse lookup

C:\> nslookup 220.227.168.115

Server: 192-168-1-200.my-site.com
Address: 192.168.1.200
Name: 65-115-71-34.my-isp.com
Address: 220.227.168.115
C :\>

102 LoveLy professionaL university