Run IP configuration program on your home system at the command 
prompt.

Windows :  ipconfig /all
Linux/Mac : ifconfig -a   (/sbin/ifconfig)

You may see several sections covering Lan (hard wired), Wireless, 
and loopback. Software such as a VPN or VMWare may create additional
sections.

Physical address : this is the actual Machine Access Code (MAC). 
This is the unique physical adress of the network interface card. 
For ethernet and WiFI, it consists of a six byte ID in two parts, 
the left 3 bytes are the OUI, Organizationally Unique Identifer 
which IDs the manufacturer. And the right 3 bytes are the NIC, 
Network Interface Controller, a unique serial number.

If you ever need to ID the manufacturer of a card, you use the 
OUI to search on line.

*

Look for your primary IP.  On Linux, it will be listed as inet 
addr. On Windows, IPv4 Address. You may have listings for both 
Wireless and LAN. 

If you are using a NAT router hub to tie several systems into 
a singe DSL line, you will most likely see 192.168.x.x. 

You can find your DSL IP by logging into hopper/turing and 
runnning 'who'. Your IP will be listed to the right. Or you 
can go to tracert.org and click "What's my IP" link.

*

Check out some other info. Better done from hopper/turing
unless you've plugged your system directly into your DSL modem.
If you are using a NAT/Wireless router to connect several 
systems, you will see the info for the NAT router rather than
your provider.

Subnet or netmask. This specifies the portion of the IPv4 address 
that can be used to identify individual systems on the local
network.

*

DHCP, DNS, and gateway.

In Linux, you can find the DHCP server listed in the IP lease. 
Check /var/lib/dhcp directory on hopper. 

For your Windows system, ipconfig will list some of this but 
it may only point to your NAT router. If you plug a system 
directly into the dsl modem, ipconfig may give you the real 
dchp server address it is using for your connection.

For the brave, if possible, connect your system directly to 
your DSL modem. Keep in mind, any other systems using your DSL
modem will be disconnected.

Run ifconfig or ipconfig, this should give you the DHCP and 
DNS servers your ISP has assigned to your connection. Remember
to put things back.

*

Resolving a DNS entry.

dig is a useful command for traciing the resolution of a DNS
name.

Try : dig eval.cs.niu.edu
Try : dig @ns1.its.niu.edu eval.cs.niu.edu

eval.cs.niu.edu is an alias name for evaluations.cs.niu.edu. 
Not the entry for eval.cs.niu.edu flags CName evaluations.cs.niu.edu.
CName is cannonical (true) name.

The first dig should find the closest DNS server, which should be
one of NIU's servers. 

The second dig specifically tells dig to ask the DNS server at
U of I.  We have an arrangement with U of I to provide backup 
DNS serivces for each other. 

However, because we now have most most systems behind a private
subnet, our firewall provides a private to public static IP 
translation. This means users who contackt one of our publically
accessable systems from on-campus do so with the private subnet
IP. But, users who are not on campus cannot see or use the 
private IP, so they receive a different NIU standard IP in the
131.156. rannge.


* 

netstat - network status.

Lists connections and ports. Various options allow a targeted
list. By itself lists all ports, even non-network ports. 

On turing/hopper, try : 

netstat --inet --numeric-ports

netstat is available on Windows systems with different options.