only 16 entries allowed for specific mac address access control

In Computer Network various types of address are introduced; each works at different layer.

Media Access Control Address is a physical address which works at Data Link Layer.

In this article, we will discuss about addressing in DLL, which is MAC Address.

MAC Address is also known as Physical Address of a network device.

MAC Address is word wide unique, since millions of network devices exists and we need to uniquely identify each.

First 6-digits (say 00:40:96) of MAC Address identifies the manufacturer, called as OUI ( Organizational Unique Identifier ).

IEEE Registration Authority Committee assign these MAC prefixes to its registered vendors.

If the LSB (least significant bit) of first octet of an address is set to zero, the frame is meant to reach only one receiving NIC.

In Layer-2 (Ethernet) Multicast address, LSB (least significant bit) of first octet of an address is set to one.

IEEE has allocated the address block 01-80-C2-xx-xx-xx (01-80-C2-00-00-00 to 01-80-C2-FF-FF-FF) for group addresses for use by standard protocols.

Ethernet frames with ones in all bits of the destination address (FF-FF-FF-FF-FF-FF) are referred as broadcast address.

Frames which are destined with MAC address FF-FF-FF-FF-FF-FF will reach to every computer belong to that LAN segment.

When device connects to the ISP, DHCP server records the MAC address and then assign IP address.

If user wants to reconnect, DHCP server checks if the device is connected before.

If so, then server tries to assign same IP address (in case lease period not expired).

In case user changed the router, user has to inform the ISP about new MAC address because new MAC address is unknown to ISP, so connection cannot be established.

Or the other option is Cloning, user can simply clone the registered MAC address with ISP.

Now router keeps reporting old MAC address to ISP and there will be no connection issue.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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Only 16 Entries Allowed For Specific Mac Address Access Control