Each NP4 processor connects to the integrated switch fabric through two XAUI interfaces: XAUI0 and XAUI1. On each NP4 processor all of the odd numbered interfaces use XAU0 and all of the even numbered interfaces use XAUI1:

NPU1

XAUI0 = port1,port3,port13, port15, port17

XAUI1 = port2, port4, port14, port16

 

NPU2

XAUI0 = port5, port7, port18, port20, port22

XAUI1 = port6, port8, port19, port21

 

NPU3

XAUI0 = port9, port11, port23, port25, port27

XAUI1 = port10, port12, port24, port26, port28

Usually you do not have to be concerned about the XAUI interface mapping. However, if an NP4 interface is processing a very high amount of traffic you should distribute that traffic among both of the XAUI interfaces connected to it. So if you have a very high volume of traffic flowing between two networks you should connect both networks to the same NP4 processor but to different XAUI links. So between even and an add numbered FortiGate-3600C ports. For example, you could connect one network to port5 and the other network to port6. In this configuration, the second NP4 processor would handle traffic acceleration and both XAUI interfaces would be processing traffic.