What is a Mac address (detail)

[yucao89]

One day someone post on the forum can i get the mac address using C or Perl and nearly no one posted him back. So now i am going to introduce people what is mac address.
MAC adress is media acess control address it is a layer 2 OSI model reference. for the osi go to www.iso.org.
It is no use when you are on the Internet. The MAC adress is the physical address burt to the ROM of a NIC (network interface card) it is 48 bits and Using a HEX to display because hex codes are base 16 and can display 4 binary number in one single character. there is trillons of MAC addresses and it is UNIQUE!!! The first 24 bits indicates the Manufactors data and the last part describes the interfaces
MAC address are for the physical adress only for LAN and for the internet we use LOGICAL address called IPs.

Not a network professional but in a future will become CCNA

[nh8as]

I would just like to add that MAC addresses are very much in use on the Internet, ethernet is more and more used not only in small LANs, but all over, many big companys, isp's etc use ethernet switching for their backbones.
In addition to this I would like to correct you a little, you compare MACs and IPs as if they are on the same "level".. In LANs we also use IPs the same way as on the Internet, but in addition we use MACs to reach the hosts on the LAN, kind of like we use DLCI numbers in frame relay etc.

MAC addresses are extremly easy to fake, so they should not be trusted when it comes to for example firewalling. (Many would belive this, because its a physical address).

(r)ARP (Address Resolution Protocol) is a protcol that resolves MAC addresses into IP addresses, and vica versa.

Under linux, you can use 'ifconfig' to se the hardware address of the ethernet NIC's attached to your system.


Not a network senior, but a CCNP.

[pjp]

Moved Cisco Certification chat here.
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