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Gigabit Ethernet uPIM Switch Overview

You can deploy a J-series device with multiport uPIMs in branch offices as an access or desktop switch with integrated routing capability, thus eliminating intermediate access switch devices from your topology. The Gigabit Ethernet uPIM provides Ethernet switching while the Routing Engine provides routing functionality, enabling you to use a single chassis to provide routing, access switching, and WAN interfaces.

You can set a multiport uPIM to three modes of operation: routing (the default), switching, or enhanced switching. Routed traffic is forwarded from any port of the Gigabit Ethernet uPIM to the WAN interface. Switched traffic is forwarded from one port of the Gigabit Ethernet uPIM to another port on the same Gigabit Ethernet uPIM. Switched traffic is not forwarded from a port on one uPIM to a port on a different uPIM.

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).

Connecting uPIMs in a Daisy-Chain

You cannot combine multiple uPIMs to act as a single integrated switch. However, you can connect uPIMs on the same chassis externally by physically connecting a port on one uPIM to a port on another uPIM in a daisy-chain fashion.

Two or more uPIMs daisy-chained together create a single switch with a higher port count than either individual uPIM. One port on each uPIM is used solely for the connection. For example, if you daisy-chain a 6-port uPIM and an 8-port uPIM, the result operates as a 12-port uPIM. Any port of a uPIM can be used for daisy-chaining.

Configure the IP address for only one of the daisy-chained uPIMs, making it the primary uPIM. The secondary uPIM routes traffic to the primary uPIM, which forwards it to the Routing Engine. This results in some increase in latency and packet drops due to oversubscription of the external link.

Only one link between the two uPIMs is supported. Connecting more than one link between uPIMs creates a loop topology, which is not supported.

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 9.2 Release or later.

Link Aggregation

You can combine multiple physical Ethernet ports to form a logical point-to-point link, known as a link aggregation group (LAG) or bundle. A LAG provides more bandwidth than a single Ethernet link can provide. Additionally, link aggregation provides network redundancy by load-balancing traffic across all available links. If one of the links should fail, the system automatically load-balances traffic across all remaining links. You can select up to eight Ethernet interfaces and include them within a link aggregation group.

Link aggregation can be used for point-to-point connections. It balances traffic across the member links within an aggregated Ethernet bundle and effectively increases the uplink bandwidth. Another advantage of link aggregation is increased availability, because the LAG is composed of multiple member links. If one member link fails, the LAG continues to carry traffic over the remaining links.

This section contains the following topics:

IGMP Snooping

Internet Group Management Protocol (IGMP) snooping regulates multicast traffic in a switched network. With IGMP snooping enabled, a LAN switch monitors the IGMP transmissions between a host (a network device) and a multicast router, keeping track of the multicast groups and associated member ports. The switch uses that information to make intelligent multicast-forwarding decisions and forward traffic to the intended destination interfaces. J-series devices support IGMPv1 and IGMPv2.

This section contains the following topics:

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