Page 5 of 8 Now that we are familiar with nslookup and ipconfig, we're ready to get down to some serious business. Let's first capture the DNS packets that are generated by ordinary Web-surfing activity.  If you are on a windows host, do the following: Use ipconfig to empty the DNS cache in your host. Open your browser and empty your browser cache. (With Internet Explorer, go to Tools menu and select Internet Options; then in the General tab select Delete Files.)  Open Wireshark and enter "dns && ip.addr == your_IP_address” into the filter, where you obtain your_IP_address (the IP address for the computer on which you are running Wireshark) with ipconfig. This filter removes all packets that neither originate nor are destined to your host or are not dns packets.  Start packet capture in Wireshark.  With your browser, visit the Web page: http://www.ietf.org Stop packet capture.  If you are on a Linux/Unix machine and do not have privileges to clear your host cache (or don't know how to) you can download this dns-tracefile that was captured while following the steps above. Or you could give it a try if you haven't been to www.ietf.org in a few days (it may not be cached). But if you don't see a DNS request, then download the tracefile. Answer the following questions What is the destination port for the DNS query message for www.ietf.org? enter a number