DePaul Information Services

Finding Your IP and MAC Address

Overview

Computers on modern-day networks are connected using a unique Internet Protocol (IP) address. Each computer can then contact other computers on the local network by sending packets of information (much like sending a letter to a recipient via postal mail) to the recipients IP address. When communicating with computers not on your local network, the packets traverse routers. More information on routing packets can be found in How Routers Work.

We use both IP addresses and MAC address when performing incident response to computer security violations on the University network. This tutorial is a brief demonstration on the steps required to find your IP and MAC address.

Finding Your IP Address on Windows 2000/XP

From the Windows Desktop click: Start, then type cmd and press [ENTER].
Enlarge the window (the output may be fairly large).
From the commandline, type ipconfig /all and press [ENTER]. You will see the following output.

C:\>ipconfig /all

Windows IP Configuration

Host Name . . . . . . . . . . . . . : jokeos
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . . : Unknown
IP Routing Enabled. . . . . . . : No
WINS Proxy Enabled. . . . . . : No
DNS Suffix Search List. . . . . : depaul.edu

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . : depaul.edu
Description . . . . . . . . . . . . . . . : Intel(R) PRO/100 VE Network Connection
Physical Address. . . . . . . . . . . : 00-0D-FF-DD-EE-FF
Dhcp Enabled. . . . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . . . . : 140.192.21.254
Subnet Mask . . . . . . . . . . . . . : 255.255.255.128
Default Gateway . . . . . . . . . . : 140.192.21.248
DHCP Server . . . . . . . . . . . . : 140.192.1.50
DNS Servers . . . . . . . . . . . . : 140.192.0.2
140.192.239.2
Lease Obtained. . . . . . . . . . . : Tuesday, April 06, 2004 4:08:57 PM
Lease Expires . . . . . . . . . . . . : Tuesday, April 13, 2004 4:08:57 PM
In this example, the IP address of the computer is 140.192.21.254 and the MAC address (aka. physical address) is 00-0D-FF-DD-EE-FF.

Finding Your IP Address on MacOS X

Start a Terminal, found in the /Applications folder.
Type /sbin/ifconfig -a. You will see the following output.

prettyos$ /sbin/ifconfig -a
lo0: flags=8049 mtu 16384
inet6 ::1 prefixlen 128
inet6 fe80::1 prefixlen 64 scopeid 0x1
inet 127.0.0.1 netmask 0xff000000
gif0: flags=8010 mtu 1280
stf0: flags=0<> mtu 1280
en0: flags=8863 mtu 1500
inet6 fe80::203:93ff:fed1:c5ac prefixlen 64 scopeid 0x4
inet 140.192.21.254 netmask 0xffffff80 broadcast 140.192.21.255
ether 00:0d:ff:dd:ee:ff
media: autoselect (1000baseTX ) status: active
supported media: none autoselect 10baseT/UTP [...]
In this example, the IP address of the computer is 140.192.21.254 and the MAC address (aka. physical address) is 00:0d:ff:dd:ee:ff.

Finding Your IP Address on FreeBSD, OpenBSD, Linux and other UNIX Variants

Enter a terminal.
Ensure that /usr/sbin and /sbin are included in your $PATH, then type ifconfig -a. To execute the command using a full path, type /sbin/ifconfig -a or /usr/sbin/ifconfig -a. You will see the following type of output.

secureos$ /sbin/ifconfig -a
lo0: flags=8049 mtu 33224
inet 127.0.0.1 netmask 0xff000000
inet6 ::1 prefixlen 128
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x6
fxp0: flags=8843 mtu 1500
address: 00:0d:ff:dd:ee:ff
media: Ethernet autoselect (1000baseTX)
status: active
inet 140.192.21.254 netmask 0xffffff80 broadcast
In the above example, the IP address is 140.192.21.254 and the hardware address is 00:0d:ff:dd:ee:ff. Variants of Linux or Solaris may vary; consult your vendors' documentation for more details.

Disclaimer

Although we have attempted to ensure this document is as precise as possible, CSRT takes no responsibility for any side-effects these procedures may incur on your computer. Please see our full disclaimer for the more information on the responsibility offered to you, the user.

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