Looking Up Information On A Local Ethernet

CS 3000 -- Lab Assignment #7

AGGREGATE ARP

Scan the man page for arp. Do arp -a. Capture the output in a file and insert comments under the lines that contain the flags P, S, U, or M. In your comments explain why the flags are in those entries and what they mean. You should be able to get most of the information you need from the man page, but you may ask for help.

ARP-AT-A-TIME

You can use arp to learn the ethernet address of a network interface. A command of the form

arp hostname

will display the current arp entry for hostname. You can use a domain name like pollux or pollux.csustan.edu for hostname. You can use the IP number (e.g. 130.17.1.55) of the host, if you know it, instead of a domain name.

In some cases you will be logged into a host H and you will do an arp X but there will be no arp entry on H for X. In that case you only need to do something that will cause H to interact with X. Usually it's easiest just to ping X. Here is an example: 
john@vega: arp pollux
pollux (130.17.1.55) -- no entry
john@vega: ping pollux
pollux.csustan.edu is alive
john@vega: arp pollux
pollux (130.17.1.55) at 8:0:20:9d:8e:9
Now you try. Use arp to get ethernet addresses on the following hosts:
Add the text of your interaction to the end of your file so it shows a script of how you got the ethernet addresses of the hosts indicated by the IP numbers above.

NSLOOKUP-AT-A-TIME

Use commands such as nslookup 130.17.31.1 to learn the domain names of the hosts identified above by IP number.

Add the text of your interaction to the end of your file so it shows a script of how you got the domain names of the hosts indicated by the IP numbers above.

PORT STATUS

Next load the man page for netstat into a web browser and do the command netstat -f inet. Append a copy of the resulting display to the end of your file record. Below that add a comment explaining (I mean really explain: make it instructive) the meaning of the command, and the meaning of each of the columns in the display. Use information from the man page.

NETWORK INTERFACE STATUS

Now do the command netstat -i. Are collisions less than 3% of output packets, and are other errors no more than half a percent of total packet volume? Excessive collisions are evidence that the network is overloaded. Other errors can be symptomatic of cabling problems.

Your computer has only one network interface card. Do you know why the command gives information about two network interfaces?

LAB REPORT

Send your file record to me at this address: tester@alcyone.csustan.edu. Make sure the subject of the e-mail reads: "Ethernet Lab." Put your name at the top of the file before sending. If you worked with a partner be sure to put his or her name there too.