Redundancy Mechanisms on Aggregated Ethernet Interfaces in a Virtual Chassis

Link Redundancy in a Virtual Chassis

By default, the router uses link redundancy, also known as port redundancy, as the default redundancy mechanism for targeted distribution on aggregated Ethernet interfaces. With link redundancy, the router assigns backup links for a subscriber based on the link with the fewest number of subscribers.

In an MX Series Virtual Chassis configured with link redundancy, the primary link and backup link can be assigned on the same Modular Port Concentrator/Modular Interface Card (MPC/MIC) module, on different MPC/MIC modules in the same member router, or on different MPC/MIC modules in different member routers. This feature provides redundancy if a link in the MX Series Virtual Chassis configuration fails.

Because link redundancy is the default redundancy mechanism, no special configuration is required on the Virtual Chassis primary router to enable it.

Module Redundancy in a Virtual Chassis

You can configure module redundancy, also known as Flexible PIC Concentrator (FPC) redundancy, to provide redundancy if a module or a link fails. The router assigns backup links for the subscriber interface on a different MPC/MIC module from the primary link, based on the link with the fewest number of subscribers among the links on different modules.

In an MX Series Virtual Chassis configured with link redundancy, the router assigns the primary link and backup link to different MPC/MIC modules. For purposes of link selection, the router gives all MPC/MIC modules in the Virtual Chassis equal weight, and disregards the role (primary or backup) of the member router in which the MPC/MIC module is installed. The router uses an algorithm to assign the primary and backup links, and is as likely to assign a primary link to an MPC/MIC module in the Virtual Chassis primary router as it is to assign the primary link to an MPC/MIC module in the Virtual Chassis backup router.

Chassis Redundancy in a Virtual Chassis

Unlike link redundancy and module redundancy, which are supported on both standalone routers and Virtual Chassis member routers, chassis redundancy is available only for member routers in an MX Series Virtual Chassis configuration.

Chassis redundancy and module redundancy use the same algorithm for link assignment, with the exception that in a Virtual Chassis with chassis redundancy configured, the router assigns the backup link to an MPC/MIC module in a member router other than the router on which the primary link resides. For example, in a two-member MX Series Virtual Chassis, if the primary link for the aggregated Ethernet bundle is assigned to an MPC/MIC module in the Virtual Chassis primary router, the router assigns the backup link to an MPC/MIC module in the Virtual Chassis backup router.

Chassis redundancy provides protection if the MPC/MIC module containing the primary link fails. In this event, the subscriber connections fail over to the backup link on the MPC/MIC module in the other member router.