[c-nsp] Cat3750: MAC addresses of L3 interfaces change after reboot ?!

[Marian Ďurkovič]

Hi all,


  Catalyst 3560/3750 /G/E switches seem to implement L3 interfaces differently
than other switches - they use unique MAC address per every L3 interface.

  MAC addresses are assigned from the MACaddr pool in the order how L3
interfaces are created, however after reboot they are assigned differently
- in the order how interfaces appear in the config.

  As an example, if you add "no switchport" to interface Gig0/1 as the last
change, it might get xxxx.xxxx.07c7 MAC address from the pool, but after reboot,
it gets xxxx.xxxx.07c1 and all other L3 interfaces get higher MAC addresses than
before.

  This creates serious problems in environments where strict MAC address
security is needed - since manual intervention is required to restore network
connectivity.

  Is there any way to change this odd behavior on Cat 3560/3750 by e.g.

- making the switch use the same MAC address for all L3 interfaces
- making the switch reuse the same MAC addresses after reboot (MAC persistence)
- configuring the MAC address on L3 interface manually?


    Thanks & kind regards,

        M.