The JUNOS software automatically creates the routing platform's management Ethernet interface, fxp0, which is an out-of-band management interface for connecting to the router. To use fxp0 as a management port, you must configure its logical interface, fxp0.0, with a valid IP address.
The JUNOS software also creates the internal Ethernet interface, fxp1, which connects the Routing Engine (re0) to the Packet Forwarding Engine. If the routing platform has redundant Routing Engines, another internal Ethernet interface, fxp2, is created to connect the second Routing Engine (re1) to the Packet Forwarding Engine.
When you enter the show interfaces command, the management Ethernet and internal Ethernet interfaces (and logical interfaces) are displayed:
user@host> show interfaces ?
... fxp0 fxp0.0 fxp1 fxp1.0 fxp2 fxp2.0 ...