Check this test:
[edit]
root@EX9204-RE0# run show chassis mac-addresses
MAC address information:
Public base address dc:38:e1:15:54:40
Public count 1984
Private base address dc:38:e1:15:5c:00
Private count 64
[edit]
root@EX9204-RE0# run show chassis fpc
Temp CPU Utilization (%) Memory Utilization (%)
Slot State (C) Total Interrupt DRAM (MB) Heap Buffer
0 Online 38 8 0 2048 17 14
1 Online 38 8 0 2048 17 14
2 Online 36 9 0 2048 9 13
[edit]
root@EX9204-RE0# run show interfaces ae13 | match Hard
Current address: dc:38:e1:15:5c:0d, Hardware address: dc:38:e1:15:5c:0d
[edit]
root@EX9204-RE0# run request chassis fpc slot 0 offline
Offline initiated, use "show chassis fpc" to verify
[edit]
root@EX9204-RE0# run request chassis fpc slot 1 offline
Offline initiated, use "show chassis fpc" to verify
[edit]
root@EX9204-RE0# run request chassis fpc slot 2 offline
Offline initiated, use "show chassis fpc" to verify
[edit]
root@EX9204-RE0# run show chassis fpc
Temp CPU Utilization (%) Memory Utilization (%)
Slot State (C) Total Interrupt DRAM (MB) Heap Buffer
0 Offline ---Offlined by cli command---
1 Offline ---Offlined by cli command---
2 Offline ---Offlined by cli command---
[edit]
root@EX9204-RE0# run show chassis mac-addresses
MAC address information:
Public base address dc:38:e1:15:54:40
Public count 1984
Private base address dc:38:e1:15:5c:00
Private count 64
[edit]
root@EX9204-RE0# run show interfaces ae13 | match Hard
Interface flags: Hardware-Down SNMP-Traps Internal: 0x4000
Current address: dc:38:e1:15:5c:0d, Hardware address: dc:38:e1:15:5c:0d
Flags: Hardware-Down Device-Down SNMP-Traps 0x4004000 Encapsulation: ENET2
[edit]
root@EX9204-RE0#
As you can see, you can assign a large continuous pool of MAC addresses. It's very unlikely that every time you need to RMA a MIC/FPC, you will get one that will have its MAC addresses from the pool of the device. Hence it makes more sense that the chassis will assign the MAC address from the its own pool to the interfaces.
Also, this KB explains how the LAG MAC addresses are assigned.
http://kb.juniper.net/InfoCenter/index?page=content&id=KB30423&actp=RSS
=====
If this worked for you please flag my post as an "Accepted Solution" so others can benefit. A kudo would be cool if you think I earned it.