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Multichassis Link Aggregation on Logical Systems Overview

On MX Series routers, EX9200, and QFX10000 switches, multichassis link aggregation (MC-LAG) enables a device to form a logical LAG interface with two or more other devices. MC-LAG provides additional benefits over traditional LAG in terms of node-level redundancy, multihoming support, and a loop-free Layer 2 network without running Spanning Tree Protocol (STP). The MC-LAG devices use Inter-Chassis Control Protocol (ICCP) to exchange the control information between two MC-LAG network devices. Starting in Junos OS Release 14.1, you can configure MC-LAG interfaces on logical systems within a router. Starting with Junos OS Release 15.1, you can configure MC-LAG interfaces on logical systems on EX9200 switches.

Note:

On QFX10008 switches, Layer 2 and Layer 3 IRB interfaces are not supported under the [edit logical-systems] hierarchy.

To configure ICCP for MC-LAG interfaces on logical systems, include the iccp statement at the [edit logical-systems logical-system-name protocols] hierarchy level. To view ICCP information for MC-LAG on logical systems, use the show iccp logical-system logical-system-name command. To view ARP statistics or remote MAC addresses for the multichassis aggregated Ethernet nodes for all or specified redundancy groups on a logical system, use the show l2-learning redundancy-groups group-name logical-system logical-system-name (arp-statistics | remote-macs) command. To view neighbor discovery (ND) statistical details for multichassis aggregated Ethernet nodes on redundancy groups of a logical group, use the show l2-learning redundancy-groups group-name logical-system logical-system-name nd-statistics command.

Logical systems enable effective, optimal segregation of a single router or switch into multiple virtual partitions, which can be configured and managed by diversified entities. Logical systems perform a subset of the actions of a physical router or switch and have their own unique routing tables, interfaces, policies, and routing instances. A set of logical systems within a single router or switch can handle the functions previously performed by several small routers or switches. As shown on the right side of Figure 1, a set of logical systems within a single router can handle the functions previously performed by several small routers.

In a network deployment that contains MC-LAG interfaces, you can configure such interfaces on logical systems contained within a router or switch. When you configure multichassis aggregated Ethernet interfaces on a logical system, you must ensure that these interfaces are added with the same multichassis aggregated Ethernet identification number and redundancy group identifier for the MC-LAG on both the peers or devices that are connected by the multichassis aggregated Ethernet interfaces. It is not necessary to specify the same logical system name on both the peers; however, you must ensure that ICCP to associate the routing or switching devices contained in a redundancy group is defined on both the peers within the logical systems of the devices. Such a configuration ensures that all the packets are transmitted using ICCP within the logical system network. The logical system information is added and removed by the ICCP process to prevent each packet from containing the logical system details. This behavior enables multiple disjoint users to employ MC-LAG capabilities within their networks transparently and seamlessly. A unique ICCP definition for a logical system is created, thereby enabling you to completely manage the ICCP parameters on one logical system without the need for access permissions to view other logical system networks on the same device. Configuration of MC-LAG interfaces on logical systems enables MC-LAG to be used across multiple routing tables and switch forwarding tables in active-active and active-standby modes of MC-LAG interfaces.

Because the Layer 2 address learning process supports logical systems, the ARP, neighbor discovery, and MAC synchronization packets that are traversing a multichassis aggregated Ethernet interface use the logical system:routing instance (LS:RI) combination to map the packets to the correct routing instance in a logical system. Link Aggregation Control Protocol (LACP) does not require the LS-RI combination to be identified because it operates on physical interfaces and is unique within a chassis. For a service, in the set of provider edge (PE) routers providing the service, the service ID distinguishes the routing instances in a logical system because it is unique for a logical system across a routing instance. MC-LAG is configured on the aggregated Ethernet (ae-) bundle interface. An ae- interface is a logical interface and is globally unique, which causes the MC-LAG configuration to be exclusive and separate for a router or switch. You can add ae- interfaces in an MC-LAG configuration to be part of a logical system and use it throughout that particular logical system.

Change History Table

Feature support is determined by the platform and release you are using. Use Feature Explorer to determine if a feature is supported on your platform.

Release
Description
15.1
Starting with Junos OS Release 15.1, you can configure MC-LAG interfaces on logical systems on EX9200 switches.
14.1
Starting in Junos OS Release 14.1, you can configure MC-LAG interfaces on logical systems within a router.