NET0183 Networks and Communications
Laboratory 6 DNS revealed (2 pages)
Part A (wireless IP configuration)
Boot up your wireless laptop computer and record the following details using ipconfig /all at the
Windows command prompt.
Wireless
Host Name
IP Address
Subnet Mask
Default Gateway
DHCP Server(s)
DNS Server(s)
length of lease
Part B (nslookup)
The tool nslookup allows a host to query any specified DNS server for a DNS record. All the various kinds
of DNS servers can be queried (root name servers, top-level domain servers, authoritative servers, etc.)
The tool nslookup sends a DNS query to the specified DNS server (or the default local DNS server if none
is specified), receives a reply from that same DNS server, and then displays the result of the query.
Perform the following nslookups at the command prompt and complete the tables below. Have your
results checked by the laboratory supervisor.
>nslookup www.mbl.is
(what is the IP address of the domain specified‘)
What is the name of the default local DNS server?
What is the IP address of the default local DNS server?
Is the answer authoritative or non-authoritative?
What is the domain name looked up?
What is the IP address of the domain name looked up?
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NET0183 Networks and Communications
>nslookup –type=NS www.mbl.is
(what is the host name of the authoritative DNS for www.mbl.is?)
What is the name of the default local DNS server?
What is the IP address of the default local DNS server?
Is the answer authoritative or non-authoritative?
What is the host name of the authoritative DNS?
What is the IP address of the authoritative DNS?
>nslookup www.unak.is pascal.mbl.is
(Use the DNS server pascal.mbl.is to return the IP address of www.unak.is.)
Describe what happens:
>nslookup www.unak.is bitsy.mit.edu
(Use the DNS server bitsy.mit.edu to return the IP address of www.unak.is.)
Describe what happens:
Part C (Wireshark trace)
Run Wireshark and use your IP address as a filter for capture or display. Capture a trace of you executing
the command: nslookup www.unak.is bitsy.mit.edu. Demonstrate to the laboratory supervisor that
you have succesfully captured a DNS query and reply. Point out to the laboratory supervisor the
authoritative DNS servers for www.unak.is described in the Wireshark capture.
Part D (Google Public DNS)
Configure your laptop computer to use Google´s public DNS servers. Carefully follow the instructions
here: http://code.google.com/speed/public-dns/. Demonstrate your new configuration to the
laboratory supervisor.
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