Understanding Switching Modes on the J-series Services Router

On the J-series Services Router, you set the uPIM to one of three operating modes: routing (the default), switching, or enhanced switching.

When you set a multiport uPIM to switching mode, the uPIM appears as a single entity for monitoring purposes. The only physical port settings that you can configure are autonegotiation, speed, and duplex mode on each uPIM port, and these settings are optional.

Routing Mode

In routing mode, the multiport uPIM has the same configuration options as any other Gigabit Ethernet interface. To configure uPIM Gigabit Ethernet interfaces in routing mode, see ”Configuring Gigabit Ethernet Interfaces—Quick Configuration” and ”Configuring Network Interfaces with a Configuration Editor.”

Switching Mode

In switching mode, the uPIM appears in the list of interfaces as a single interface, which is the first interface on the uPIM—for example, ge-2/0/0. You can optionally configure each uPIM port only for autonegotiation, speed, and duplex mode. A uPIM in switching mode can perform the following functions:

• Layer 3 forwarding—Routes traffic destined for WAN interfaces and other PIMs present on the chassis.
• Layer 2 forwarding—Switches intra-LAN traffic from one host on the LAN to another LAN host (one port of uPIM to another port of same uPIM).

Enhanced Switching Mode

In enhanced switching mode, each port can be configured for switching or routing mode. This usage differs from the routing and switching modes, in which all ports must be in either switching or routing mode. The uPIM in enhanced switching mode provides the following features:

• Supports configuration of different types of VLANs and inter-VLAN routing
• Supports Layer 2 control plane protocols such as Spanning Tree Protocol (STP) and Link Aggregation Control Protocol (LACP)
• Supports port-based Network Access Control (PNAC) by means of authentication servers

Note: You can configure uPIM in enhanced switching mode only in JUNOS 9.2 or later releases.