Overview of Interface Fundamentals

Learn about network interfaces and their types, and the characteristics of special interface types.

Network interfaces connect devices to send and receive network traffic. Network Interfaces provide link-layer and network-layer properties for the operating system and protocols to handle frames and packets.

A network interface, also known as a network interface controller, network interface card, or network adapter, is a hardware component that enables computers to access an interconnection network for communication and synchronization. Network interface acts as a port for sending or receiving packets. A network interface provides two interfaces: one for the computer (host) side and another for the network side. It translates the host interface protocol to the network protocol and vice versa, converting between different physical media.

Figure 1: Network Interfaces Network topology diagram with two laptops connected via en0 interfaces, cloud representing internet, device with eth0 interface, switch sw0, bridge br0, and wireless device wifi0 showing wired and wireless connections.

Network topology diagram with two laptops connected via en0 interfaces, cloud representing internet, device with eth0 interface, switch sw0, bridge br0, and wireless device wifi0 showing wired and wireless connections.

Table 1: Network Interfaces Types
Type	Description
Aggregated Ethernet interfaces	Group Ethernet interfaces at the physical layer to form a single link-layer interface, also known as a link aggregation group (LAG) or bundle. These aggregated Ethernet interfaces help to balance traffic and increase the uplink bandwidth. See Aggregated Ethernet Interfaces Overview.
LAN access interfaces	Use these interfaces to connect to other servers, storage, and switches. When you power on switches and use the factory-default configuration, the software automatically configures interfaces in access mode for each of the network ports. The default configuration also enables autonegotiation for both speed and link mode.
Power over Ethernet (PoE) interfaces	Use the PoE network ports to connect VoIP telephones, wireless access points, video cameras, and point-of-sale devices to safely receive power from the same access ports that are used to connect personal computers to the network. PoE interfaces are enabled by default in the factory configuration. See Understanding PoE on EX Series Switches.
Trunk interfaces	You can connect access switches to a distribution switch or customer-edge (CE) switches or routers. To use a port for this type of connection, you must explicitly configure the network interface for trunk mode. You must also configure the interfaces from the distribution switch or CE switch to the access switches for trunk mode.
Channelized Interfaces	Depending on the device and software package, 40-Gbps QSFP+ ports can be configured to operate as the following types of interfaces: 10-Gigabit Ethernet interfaces (xe) 40-Gigabit Ethernet interfaces (et and xle) 40-Gigabit data plane uplink interfaces (fte) When an et port is channelized to four xe ports, a colon is used to signify the four separate channels. For example, on a QFX3500 standalone switch with port 2 on PIC 1 configured as four 10-Gigabit Ethernet ports, the interface names are xe-0/1/2:0, xe-0/1/2:1, xe-0/1/2:2, and xe-0/1/2:3 You cannot configure channelized interfaces to operate as Virtual Chassis ports.
Ethernet Interfaces	Configure Gigabit Ethernet, 10-Gigabit Ethernet, 40-Gigabit Ethernet interfaces to connect to other servers, storage, and switches. You can configure 40-Gigabit data plane uplink ports to connect a Node device to an Interconnect devices as well as for Virtual Chassis ports (VCPs).
Fibre Channel interfaces	Use Fibre Channel interfaces to connect the switch to a Fibre Channel over Ethernet (FCoE) forwarder or a Fibre Channel switch in a storage area network (SAN). You can configure Fibre Channel interfaces only on ports 0 through 5 and 42 through 47 on QFX3500 devices. Fibre Channel interfaces do not forward Ethernet traffic. See Overview of Fibre Channel.
Multichassis aggregated Ethernet (MC-AE) interfaces	Group a LAG on one standalone switch with a LAG on another standalone switch to create a MC-AE. The MC-AE provides load balancing and redundancy across the two standalone switches.
Tagged-access mode interfaces	Use tagged-access interfaces to connect a switch to an access layer device. Tagged-access interfaces can accept VLAN-tagged packets from multiple VLANs.

Table 2: Special Interfaces Types
Type	Purpose
Console port	Each switch has a serial port, labeled CON or CONSOLE, for connecting tty-type terminals to the switch using standard PC-type tty cables. The console port does not have a physical address or IP address associated with it. However, it is an interface since it provides access to the switch.
Loopback	All switches have this software-only virtual interface that is always up. The loopback interface provides a stable and consistent interface and IP address on the switch.
Management interface	Management interfaces are the primary interfaces for accessing the device remotely. You can use the management interface to access the device over the network using utilities such as `ssh` and `telnet`. You can configure the device from anywhere, regardless of its physical location. SNMP can use the management interface to gather statistics from the device. The Juniper Networks Junos operating system (Junos OS) for switches automatically creates the switch's management Ethernet interface, me0. The management Ethernet interface provides an out-of-band method for connecting to the switch. To use me0 as a management port, you must configure its logical port, me0.0, with a valid IP address. You can connect to the management interface over the network using utilities such as SSH or Telnet. SNMP can use the management interface to gather statistics from the switch. (The management interface me0 is analogous to the fxp0 interfaces on routers running Junos OS.) Before you can use management interfaces, you must configure the logical interfaces with valid IP addresses. Juniper Networks does not support configuring two management interfaces in the same subnet.
Integrated Routing and Bridging (IRB) Interface or Routed VLAN Interface (RVI)	Switches use an integrated routing and bridging (IRB) interface or Routed VLAN Interface (RVI) to route traffic from one broadcast domain to another and to perform other Layer 3 functions such as traffic engineering. These functions are typically performed by a router interface in a traditional network. The IRB interface or RVI functions as a logical router, eliminating the need for having both a switch and a router. Configure these interfaces as part of a broadcast domain or Virtual Private LAN Service (VPLS) routing instance for L3 traffic to be routed from. See Understanding Integrated Routing and Bridging.
Virtual Chassis port (VCP) interfaces	On a Virtual Chassis port, you can access the primary device and configure all members of the Virtual Chassis through any member's console port. For more information about the console port in a Virtual Chassis, see Understanding Global Management of a Virtual Chassis.
Virtual management Ethernet (VME) interface	VME interface is a logical interface that is used for Virtual Chassis configurations and allows you to manage all the members of the Virtual Chassis through the primary device. For more information about the VME interface, see Understanding Global Management of a Virtual Chassis.