Excercise1 : Use Ipconfig and Nslookup to work with DNS.

1. Open a command prompt window.
2. To see a list of recent DNS lookups, type ipconfig /displaydns and press Enter.
3. To perform a DNS lookup, type ping www.course.com and press Enter. Display the DNS cache again.
4. You should see a DNS record for www.course.com that includes the IP address and other information. Another field in the DNS cache is a TTL value, which is different from the TTL in an IP packet. This DNS TTL value is sent by the DNS server maintaining the www.course.com record. It’s measured in seconds and tells your DNS client how long to cache the DNS record as a safeguard against clients holding on to DNS records whose IP addresses might have changed.
5. Type nslookup www.course.com and press Enter. Your DNS server’s name and IP address are displayed, along withthe name and IP address of www.course.com. You use Nslookup to look up a host’s IP address without actually communicating with it.
6. Type nslookup and press Enter. You enter Nslookup’s interactive mode. Type www.google.com and press Enter. Notice that more than one address is returned along with one or more aliases (other names that www.google.comgoes by). Type www.google.com again (or press the up arrow to repeat the last line you typed) and press Enter. Youshould see the IP addresses returned in a different order. (If you don’t, keep trying, and the order will change.) Thewww.google.com page can be reached by a number of different IP addresses,

nd the addresses are returned in a different order so that a different server is used each time, which is called load balancing.

7. Type 198.60.123.100 and press Enter. Nslookup is also used to do reverse lookups, in which the IP address is given and the hostname is returned.