| C.3. Forcing particular MAC addresses | ||
|---|---|---|
 | Appendix C. MAC Addresses usage |  |
| C.3. Forcing particular MAC addresses | ||
|---|---|---|
| | Appendix C. MAC Addresses usage | |
On rare occasions, it may be necessary or desirable to use specific MAC addresses for
particular connections. In these cases, you may configure mac-suffix on a
subnet, interface or PPPoE object. This allows you to set the end byte(s) of the MAC to
determine which MAC address is used from within the FB9000's block of allocated MACs.
It is also possible to change the base MAC address and hence change the entire block of
allocated MACs. This can be done by setting spoof-mac under "System settings".
This should not be necessary under normal circumstances but if you use this feature, make sure
that the MAC addresses do not clash with other devices on any LAN segments to which the
FB9000 is connected.
Be careful when changing MAC addresses, as this can cause disruption. As stated above, it is generally desirable for MAC addresses to be consistent. Connections will drop because it can take time for other network equipment to become aware of the changes. Some equipment (often at the ISP level) does not expect MAC addresses to change at all.
Because MAC suffixes are stored in persistent data (separately from the config), changes to
MACs will persist even if the mac-suffix is later removed. This should
minimise unnecessary changes to suffixes, but this means that even a 'Test' save of the config
can cause permanent changes. Also note that if you are explicitly setting a MAC suffix that is
already in use on a different subnet, then that subnet will be assigned a new MAC.
| |  | |
| C.2. How the FireBrick allocates MAC addresses |  | C.4. MAC address on label |