Permanent Interfaces

Each router has two permanent interfaces:

• Management Ethernet interface—Provides an out-of-band method for connecting to the router. You can connect to the management interface over the network using utilities such as ssh and Telnet. SNMP can use the management interface to gather statistics from the router.
• Internal Ethernet interface—Connects the Routing Engine (the portion of the router running the JUNOS Internet software) to the System Control Board (SCB), the System and Switch Board (SSB), the Forwarding Engine Board (FEB), or the System and Forwarding Module (SFM), depending on router model, which is part of the Packet Forwarding Engine. The router uses this interface as the main communications link between the JUNOS software and the components of the Packet Forwarding Engine and runs the embedded microkernel.

The JUNOS software boots the Packet Forwarding Engine hardware, including the control board (SCB, SSB, FEB, or SFM), Flexible PIC Concentrators (FPCs), and Physical Interface Connectors (PICs). When these components are running, the control board uses the internal Ethernet interface to transmit hardware status information to the JUNOS software. Information transmitted includes the internal router temperature, the condition of the fans, whether an FPC has been removed or inserted, and information from the craft interface on the LCD display panel. The internal Ethernet interface is configured automatically when the JUNOS software boots.

Each router also has two serial ports, labeled console and auxiliary, for connecting tty-type terminals to the router using standard PC-type tty cables. Although these ports are not network interfaces, they do provide access to the router.