Device Interfaces Overview

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

• Permanent interfaces—Interfaces that are always present in the device.

  Permanent interfaces in the device consist of management Ethernet interfaces and internal Ethernet interfaces, both of which are described separately in the following topics:

  • Understanding Management Ethernet Interfaces

  • Understanding Internal Ethernet Interfaces

• Transient interfaces—Interfaces that can be inserted into or removed from the device depending on your network configuration needs.

• Networking interfaces—Interfaces that primarily provide traffic connectivity.

• Services interfaces—Interfaces that provide specific capabilities for manipulating traffic before it is delivered to its destination.

Each interface has an interface name, which specifies the media type, the slot in which the Flexible PIC Concentrator (FPC) is located, the location on the FPC where the PIC is installed, and the PIC port. The interface name uniquely identifies an individual network connector in the system. You use the interface name when configuring interfaces and when enabling various functions and properties, such as routing protocols, on individual interfaces. The system uses the interface name when displaying information about the interface, such as in the show interfaces command.

The interface name is represented by a physical part, a channel part, and a logical part in the following format:

The channel part of the name is optional for all interfaces except channelized DS3, E1, OC12, and STM1 interfaces.

The following sections provide interface naming configuration guidelines:

• Physical Part of an Interface Name
• Logical Part of an Interface Name
• Separators in an Interface Name
• Chassis Interface Naming

When you configure an interface, you are effectively specifying the properties for a physical interface descriptor. In most cases, the physical interface descriptor corresponds to a single physical device and consists of the following parts:

• The interface name, which defines the media type

• The slot in which the FPC is located

• The location on the FPC in which the PIC is installed

• The PIC port

• The interface’s channel and logical unit numbers (optional)

Each physical interface descriptor can contain one or more logical interface descriptors. These descriptors enable you to map one or more logical (or virtual) interfaces to a single physical device. Creating multiple logical interfaces enables you to associate multiple virtual circuits, data-link connections, or virtual LANs (VLANs) with a single interface device.

Each logical interface descriptor can have one or more family descriptors to define the protocol family that is associated with and allowed to run over the logical interface.

The following protocol families are supported:

• Internet Protocol version 4 (IPv4) suite (inet)

• Internet Protocol version 6 (IPv6) suite (inet6)

• Ethernet (ethernet switching)

• Circuit cross-connect (CCC)

• Translational cross-connect (TCC)

• International Organization for Standardization (ISO)

• Multiprotocol Label Switching (MPLS)

Finally, each family descriptor can have one or more address entries, which associate a network address with a logical interface and hence with the physical interface.

You configure the various interface descriptors as follows:

• You configure the physical interface descriptor by including the interfaces interface-name statement.

• You configure the logical interface descriptor by including the unit statement within the interfaces interface-name statement or by including the .logical descriptor at the end of the interface name, as in et-0/0/0.1, where the logical unit number is 1, as shown in the following examples:

• You configure the family descriptor by including the family statement within the unit statement.

• You configure address entries by including the address statement within the family statement.

To display a configuration, use either the show command in configuration mode or the show configuration top-level command. Interfaces are listed in numerical order, first from lowest to highest slot number, and then from lowest to highest PIC number, and finally from lowest to highest port number.

Table 1 lists encapsulation support by interface type.

Within a Juniper device, internal Ethernet interfaces provide communication between the Routing Engine and the Packet Forwarding Engines. Junos OS Evolved automatically configures internal Ethernet interfaces when Junos OS Evolved boots. Junos OS Evolved boots the packet-forwarding component hardware. When these components run, the Control Board (CB) uses the internal Ethernet interface to transmit hardware status information to the Routing Engine. Hardware status information includes the internal router temperature, the condition of the fans, whether an FPC has been removed or inserted, and information from the LCD on the craft interface.

• Most Juniper devices—Junos OS Evolved creates the internal Ethernet interface. The internal Ethernet interface connects the Routing Engine re0 to the Packet Forwarding Engines.

  If the device has redundant Routing Engines, another internal Ethernet interface is created on each Routing Engine (re0 and re1) in order to support fault tolerance. Two physical links between re0 and re1 connect the independent control planes. If one of the links fails, both Routing Engines can use the other link for IP communication.

Each device also has one or two serial ports, labeled CON (console) or AUX (auxiliary), for connecting tty type terminals to the device using standard PC-type tty cables. Although these ports are not network interfaces, they do provide access to the device. Refer to your devices hardware guide for details.