## Problem

Often end user IT departments will need to know the MAC address of Ethernet equipment, including devices such as the Lighting Router, in order to allow the devices to communicate on their network. This can be calculated from the router's serial number as follows using either a calculator or Excel.

## Solution

The MAC address contains 6 bytes, each byte being represented by 2 hexadecimal digits (0-9,A-Z), making a total of 12 hexadecimal digits

For clarity the each byte of the MAC address is traditionally separated by colons

The MAC address fixed part for routers is the first 7 hexadecimal digits of 00:E0:AA:E1:23:45 i.e. 3 and a half bytes

The MAC address variable part is the last 5 hexadecimal digits of 00:E0:AA:E1:23:45 i.e. 2 and a half bytes

The MAC address variable part is the router’s serial number.

__ __

__Example 1__

Router Serial Number 25259

Calculator in **Program** Mode

Click **Hex**. The answer will change to 62AB

Helvar Prefix always 7 hexadecimal digits 00:E0:AA:E

Then add __5__ hexadecimal digits from the calculator result, __adding a leading 0 where necessary____,__ 0:62:AB

MAC address 00:E0:AA:E0:62:AB

__Example 2__

Router Serial Number 98907

Hex Serial Number 1825B

Helvar Prefix always 7 hexadecimal digits 00:E0:AA:E

Then add __5__ hexadecimal digits from the calculator result, no leading zero being necessary in this case, 1:82:5B

MAC address 00:E0:AA:E1:82:5B

__Example 3__

Using Excel, enter the serial number into cell B3 then paste the following formula into the cell C3

="00E0AAE" & RIGHT("00000" & DEC2HEX(B3),5)

To get the version with colons, paste the following formula into cell D3

=LEFT(C3,2) & ":" & MID(C3,3,2) & ":" & MID(C3,5,2) & ":" & MID(C3,7,2) & ":" & MID(C3,9,2) & ":" & MID(C3,11,2)

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