Q: what is the relationship between interface and the port number displayed in system on USG50?
1. There are 1 WAN interface, 4 LAN interfaces, 1 console interface, 1 USB interface, power switch and 1 plug from left to right on back panel of USG50.
2. Ethernet 0/0/0 is the WAN interface.
Ethernet 0/0/1 is the LAN interface.
There is only one logical interface, but there are 4 physical interfaces connected by a switch chip in LAN interface. Logically, it means a 4-interfaces switch is connected with this LAN interface.
Secp 0/0/2 is the interface of USG50 IPSEC encryption card.
Because the data communication form of encryption card is similar to CPU, communicated by PCI bus. So the system processes the data of encryption card as Ethernet data. But the difference is that the data of encryption card comes from CPU and sends back after encryption.
IPSEC encryption card is a chip which looks like a CPU in the PCB and is invisible for normal user.