Types of Interfaces

Interfaces can be can be permanent or transient, and are used for networking or services:

• Permanent interfaces—Interfaces that are always present in the routing platform.
• Transient interfaces—Interfaces that can be inserted into or removed from the routing platform depending on your network configuration needs.
• Networking interfaces—Interfaces, such as Ethernet or SONET/SDH interfaces, that primarily provide traffic connectivity.
• Services interfaces—Interfaces that provide specific capabilities for manipulating traffic before it is delivered to its destination.

Permanent Interfaces

Each routing platform has two permanent interfaces:

• Management Ethernet interface—For M-series, T-series, and MX-series routing platforms, the JUNOS software automatically creates the routing platform’s management Ethernet interface, fxp0. The management Ethernet interface provides an out-of-band method for connecting to the routing platform. To use fxp0 as a management port, you must configure its logical port, fxp0.0, with a valid IP address. You can connect to the management interface over the network using utilities such as ssh and telnet. Simple Network Management Protocol (SNMP) can use the management interface to gather statistics from the routing platform.
• For the J-series Services Routers, you can use any of the built-in Ethernet ports as a management interface. To use a built-in interface as a management Ethernet interface, configure it with a valid IP address. For information about establishing basic connectivity and configuring a management port, see the Getting Started guide for your router.

• Internal Ethernet interface—The JUNOS software creates the internal Ethernet interface fxp1. The internal Ethernet interface connects the Routing Engine re0 (the portion of the routing platform running the JUNOS software) 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.

The JUNOS software boots the packet forwarding component hardware. 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 routing platform temperature, the condition of the fans, whether an FPC has been removed or inserted, and information from the craft interface on the LCD panel. The internal Ethernet interface is configured automatically when the JUNOS software boots.

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

Transient Interfaces

The M-series and T-series routing platforms contain slots for installing FPC boards, and each FPC can accommodate up to four PICs. The PICs provide the actual physical interfaces to the network. The MX-series routing platforms contain slots for installing DPC boards, and the DPC provides the physical interfaces to the network. These physical interfaces are transient interfaces of the routing platform. They are referred to as transient because you can hot-swap a DPC or FPC and its PICs at any time.

You can insert any FPC or DPC into any slot of the appropriate routing platform. You can generally place any combination of PICs in any location on an FPC. (You are limited by the total FPC bandwidth, and by the fact that some PICs physically require two or four of the PIC locations on the FPC.)

You must configure each of the transient interfaces based on the slot in which the FPC is installed, the location in which the PIC is installed, and for some PICs, the port to which you are connecting.

You can configure the interfaces on PICs that are already installed in the routing platform as well as interfaces on PICs that you plan to install later. The JUNOS software detects which interfaces are actually present, so when the software activates its configuration, it activates only present interfaces and retains the configuration information for the interfaces that are not present. When the JUNOS software detects that an FPC containing PICs has been inserted into the routing platform, the software activates the configuration for those interfaces.

Services Interfaces

Services interfaces enable you to incrementally add services to your network. The JUNOS software supports the following services PICs:

• Adaptive Services (AS) PICs—Allow you to provide multiple services on a single PIC by configuring a set of services and applications. The AS PICs offer a special range of services you configure in one or more service sets.
• ES PIC—Provides a security suite for the IP version 4 (IPv4) and IP version 6 (IPv6) network layers. The suite provides functionality such as authentication of origin, data integrity, confidentiality, replay protection, and nonrepudiation of source. It also defines mechanisms for key generation and exchange, management of security associations, and support for digital certificates.
• Monitoring Services PICs—Enable you to monitor traffic flow and export the monitored traffic. Monitoring traffic allows you to gather and export detailed information about IPv4 traffic flows between source and destination nodes in your network; sample all incoming IPv4 traffic on the monitoring interface and present the data in cflowd record format; perform discard accounting on an incoming traffic flow; encrypt or tunnel outgoing cflowd records, intercepted IPv4 traffic, or both; and direct filtered traffic to different packet analyzers and present the data in its original format. On a Monitoring Services II PIC, you can configure either monitoring interfaces or collector interfaces. A collector interface allows you to combine multiple cflowd records into a compressed ASCII data file and export the file to an FTP server.
• Multilink Services, MultiServices, Link Services, and Voice Services PICs—Enable you to split, recombine, and sequence datagrams across multiple logical data links. The goal of multilink operation is to coordinate multiple independent links between a fixed pair of systems, providing a virtual link with greater bandwidth than any of the members.
• Tunnel Services PIC—By encapsulating arbitrary packets inside a transport protocol, tunneling provides a private, secure path through an otherwise public network. Tunnels connect discontinuous subnetworks and enable encryption interfaces, virtual private networks (VPNs), and Multiprotocol Label Switching (MPLS).
• On M-series and T-series routing platforms, logical tunnel interfaces allow you to connect logical routers, virtual routers, or VPN instances. For more information about VPNs, see the JUNOS VPNs Configuration Guide. For more information about configuring tunnels, see the JUNOS Services Interfaces Configuration Guide.

• Services (J-series)—On J-series Services Routers, the lt interface is an internal interface only and is not associated with a physical medium or PIM. You can configure the logical tunnel interface to provide class-of-service (CoS) support for data link switching (DLSw) traffic and real-time performance monitoring (RPM) probe packets. For more information, see the J-series Services Router Basic LAN and WAN Access Configuration Guide.

  Note: The lt interface on the J-series Services Router does not support logical routers.