Appendix C. MAC Addresses usage

Ethernet networks use 48 bit MAC addresses. These are globally unique and allocated by the equipment manufacturer from a pool of addresses that is defined by the first three octets (bytes), which identify the organization, and are known as the Organizationally Unique Identifier (OUI). OUIs are issued by the IEEE - more information, and a searchable database of existing OUIs are available at http://standards.ieee.org/develop/regauth/oui/

MAC addresses are commonly written as six groups of two hexadecimal digits, separated by colons or hyphens.

FB2500s currently ship with an OUI value of 00:03:97.

In principle the FireBrick could have a single MAC address for all operations. However, practical experience has led to the use of multiple MAC addresses on the FireBrick. A unique block of addresses is assigned to each FireBrick, with the size of the block dependent on the model.

Most of the time, FB2500 users do not need to know what MAC addresses the product uses. However, there are occasions where this information is useful, such as when trying to identify what IP address a DHCP server has allocated to a specific FB2500. For information on how MAC addresses are used by the FB2500, please refer to this article on the FireBrick website

The label attached to the bottom of the FB2500 shows what MAC address range that unit uses, using a compact notation, as highlighted in Figure C.1 :-

Figure C.1. Product label showing MAC address range

In this example, the range is specified as :-

000397:147C-F

this is interpreted as :-

Therefore this range spans 00:03:97:14:7C:00 to 00:03:97:14:7F:FF inclusive (1024 addresses). If you trying to identify an IP address allocation, note that the exact address used within this range depends on a number of factors ; generally you should look for an IP address allocation against any of the addresses in the range.

Alternatively, if the range specification doesn't include a hyphen, it specifies that all addresses in the range start with this 'prefix' - the first address in the range will have zero for all the remaining digits, and the last address in the range will have F for all the remaining digits. For example :-

000397:147C

is interpreted as :

Therefore this range spans 00:03:97:14:7C:00 to 00:03:97:14:7C:FF inclusive (256 addresses).

If your DHCP server shows the name of the client (FB2500) that issued the DHCP request, then you will see a value that depends on whether the system name is set on the FB2500, as shown in Table C.1. Refer to Section 4.2.1 for details on setting the system name.

If the FB2500's system name is set, and your DHCP server shows client names, then this is likely to be the preferred way to locate the relevant DHCP allocation in a list, rather than trying to locate it by MAC address. If the FB2500 is in a factory-reset state, then the system name will not be set, and you will have to locate it by MAC address.